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Illustration depicting formed elements of blood
Picture Attribution:
By staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436., CC BY 3.0 <;, via Wikimedia Commons. File URL:
What is Blood?

What is Blood? It’s a good place to start. Although seemingly a simple question, the answer is quite complicated. First, it’s necessary to know that blood comprises platelets, white and red blood cells, and plasma. Then, it is important to understand how blood is made by the human body and the various disorders that can arise – all as described below.

The platelets, the smallest of our blood cells, can only be seen under a microscope. Their purpose in life is to come to your rescue when you suffer a cut. A normal platelet count ranges from 150,000 to 450,000 platelets per microlitre of blood. Having more than 450,000 platelets is a condition called thrombocytosis, whereas having less than 150,000 is known as thrombocytopenia. The number of platelets you have is found via a routine blood test called a complete blood count (CBC)[1].

White blood cells
White blood cells (aka leukocytes or white corpuscle) are part of the immune system that protects your body from illness and disease. These cells circulate through your bloodstream and tissues to respond to injury or disease by attacking any unknown organisms that enter your body. They account for a small part (1%) of your blood, but their impact is huge – by producing antibodies or fighting viruses, bacteria, and other unwanted invaders that threaten your health. The cells are made in the bone marrow and are stored in your blood and lymph tissues. Because some white blood cells (called neutrophils) have a short life of less than a day, your bone marrow is constantly making them[2].

In adults, the bone marrow produces 60/70% of the white cells. The lymphatic tissues, particularly the thymus, the spleen, and the lymph nodes, produce the lymphocytes (comprising 20/30% of the white cells). The reticuloendothelial tissues of the spleen, liver, lymph nodes and other organs produce the monocytes (4% to 8% of the white cells). A healthy adult human has between 4,500 and 11,000 white blood cells per cubic millimetre of blood.

Blood circulating in our bodies is composed of about 55% plasma, 40% red blood cells, 4% platelets, and 1% white blood cells. Of the white blood cells in blood circulation, neutrophils are the most abundant.[3] Fluctuations in white cell numbers occur during the day; lower values are obtained during rest and higher values during exercise. The survival of white blood cells, as living cells, depends on their continuous production of energy. The chemical pathways utilised are more complex than those of the red cells and are similar to those of other tissue cells. White cells, containing a nucleus and able to produce ribonucleic acid (RNA), can synthesise protein[4].

Red blood cells[5]
Red blood cells (RBC) contain a substance called haemoglobin, which transports oxygen around the body. The amount of oxygen delivered to your body’s tissues depends on the number of your red blood cells and how well they work. An RBC count is usually carried out as part of a full blood cell (FBC) count. Women typically have a lower RBC count than men, and the level of red blood cells tends to decrease with age. A normal RBC count would be:

  • Men: 4.7 to 6.1 million cells per microlitre (cells/mcL)
  • Women: 4.2 to 5.4 million cells/mcL

Picture Credit: “Red Blood cells” by SciTechTrend is marked with CC PDM 1.0

The results of an RBC count can be used to help diagnose blood-related conditions, such as iron deficiency anaemia (where there are fewer red blood cells than normal). A low RBC count could also indicate a vitamin B6, B12 or folate deficiency, but it may also signify internal bleeding, kidney disease or malnutrition (where a person’s diet doesn’t contain enough nutrients to meet their body’s needs). A high RBC count could be caused by several health conditions or health-related factors, including:

The cytoplasm[6] of a red blood cell is rich in haemoglobin, the iron-containing biomolecule[7] that can bind oxygen and is responsible for the red colour of the cells and the blood. Each human red blood cell contains approximately 270 million haemoglobin molecules[8]. The cell membrane is composed of proteins and lipids, and this structure provides properties essential for physiological cell function – such as deformability and stability of the blood cell while traversing the circulatory system and, specifically, the capillary network[9].

In humans, mature red blood cells are flexible biconcave disks. They lack a cell nucleus and organelles to accommodate maximum space for haemoglobin; they can be viewed as sacks or pockets of haemoglobin, with a plasma membrane as the sack. Approximately 2.4 million new erythrocytes are produced per second in human adults[10]. The cells develop in the bone marrow and circulate for about 100–120 days in the body before their components are recycled by macrophages.[11]

Cleveland Medical[12] very usefully say that red blood cell conditions have either a low or high red blood cell count. They say the medical conditions that affect this include:

Low red blood cell count

High red blood cell count

Anaemia: Your blood carries less oxygen than normal and causes your body to feel cold, tired and weak.

Polycythemia Vera: A high red blood cell count causes your blood to thicken, leading to a heart attack or stroke.

Blood loss: Your body loses more blood cells than it can produce.

Congenital heart disease: One or more structures in your heart are irregular due to not forming completely during the development of the foetus.

Bone marrow disorder: You experience damage to your bone marrow, where red blood cells           form (leukaemia, lymphoma).

Lung disease: The tissue in your lungs scars from emphysema, COPD[13] or pulmonary fibrosis.

Cancer: Certain cancers and chemotherapy treatments for cancer can affect the number of       red blood cells produced by your body.

Hypoxia: The oxygen level in your blood is low.


Carbon monoxide: Smoking increases your chance of exposure to carbon monoxide.

Plasma is the yellowish liquid in your blood that carries platelets, red blood cells and white blood cells around the body. About 55% of our blood is plasma, and the remaining 45% are red blood cells, white blood cells, and platelets suspended in the plasma. Plasma is about 92% water. It also contains vital proteins such as albumin, gamma globulin and anti-haemophilic factor, and 1% mineral salts, sugars, fats, hormones and vitamins. Plasma serves several important functions in our body:

  • Helping maintain blood pressure and volume.
  • Supplying critical proteins for blood clotting and immunity.
  • Carrying electrolytes such as sodium and potassium to our muscles.
  • Helping maintain a proper pH balance in the body, which supports cell function.
  • Fighting infection with antibodies, known as immunoglobulins.

Plasma is commonly given to trauma, burn and shock patients and people with severe liver disease or multiple clotting factor deficiencies. It helps boost the patient’s blood volume, which can prevent shock, and helps with blood clotting. Pharmaceutical companies use plasma to treat conditions such as immune deficiencies and bleeding disorders.

The Bone Marrow
The bone marrow is the spongy material in the centre of some of our bones. It makes cells known as stem cells. Stem cells are early blood cells that develop into three different types of blood cells:

  • red blood cells, which carry oxygen to all cells in the body
  • white blood cells, which fight infections and form part of our immune system
  • platelets, which help the blood clot to prevent bleeding.

Blood Conditions[15]
Common blood disorders include anaemia, bleeding disorders such as haemophilia, blood clots, and blood cancers such as leukaemia, lymphoma, and myeloma. Talking to your GP is the first step to take if you believe you may have a blood condition.

The field of haematology covers a wide spectrum of disorders. Some of these disorders are benign, meaning they resolve completely with therapy or do not cause symptoms and do not affect overall lifespan. Some are chronic and lifelong but again do not affect longevity. Other blood disorders are more serious and can cause chronic illness or are life-threatening. A list of conditions of blood (but read the footnote)[16] is as follows:

  • Acute leukaemias
  • Acute lymphocytic leukaemia
  • Acute myelogenous leukaemia
  • Amyloidosis
  • Anaemia: Either due to chronic disease or iron deficiency – an abnormally low number of red blood cells in the blood. Fatigue and breathlessness can result, although anaemia often causes no noticeable symptoms.
  • Antiphospholipid syndrome
  • Aplastic anaemia
  • Autoimmune hemolytic anaemia, an immune-mediated disease causing a low red blood cell count
  • Autoimmune hemolytic anaemias
  • Autoimmune thrombocytopenia
  • Bacteremia: Bacterial infection of the blood. Blood infections are serious and often require hospitalisation and continuous antibiotic infusion into the patient’s veins.
  • Benign hematologic conditions
  • Bleeding disorders
  • Blood clots (not life-threatening)
  • Cancer
  • Castleman disease
  • Chronic lymphocytic leukaemia
  • Chronic myelogenous leukaemia (CML) – excessive white cell production causing leukaemia
  • Chronic myelomonocytic leukaemia
  • Cryoglobulinemia
  • Cutaneous T-cell lymphoma
  • Deep venous thrombosis (DVT): A blood clot in a deep vein, usually in the leg. DVTs are dangerous because they may become dislodged and travel to the lungs, causing a pulmonary embolism (PE).
  • Disseminated intravascular coagulation (DIC): An uncontrolled process of simultaneous bleeding and clotting in very small blood vessels. DIC usually results from severe infections or cancer.
  • Essential thrombocythemia
  • Fanconi anaemia
  • Haemochromatosis: A disorder causing excessive levels of iron in the blood. The iron deposits in the liver, pancreas and other organs and causes liver problems and diabetes.
  • Haemophilia: An inherited (genetic) deficiency of certain blood clotting proteins. Frequent or uncontrolled bleeding can result from haemophilia.
  • Haemorrhage (bleeding): Blood leaking out of blood vessels may be obvious from a wound penetrating the skin. Internal bleeding (such as into the intestines or after a car accident) may not be immediately apparent.
  • Hairy cell leukaemia
  • Heavy chain disease
  • Hematoma: A collection of blood inside the body tissues. Internal bleeding often causes a haematoma.
  • Hemoglobinopathies
  • Hemolytic anaemia: This is Anemia caused by the rapid bursting of large numbers of red blood cells (hemolysis). An immune system malfunction is one cause.
  • Hereditary hemolytic anaemias
  • Hodgkin’s lymphoma (Hodgkin’s disease)
  • Hypercoagulable state: Numerous conditions can result in the blood being prone to clotting. A heart attack, stroke, or blood clots in the legs or lungs can result.
  • Hypereosinophilic syndrome
  • Idiopathic thrombocytopenic purpura (ITP), an immune-mediated disease causing a low platelet count
  • Immune thrombocytopenia (ITP)
  • Iron deficiency anaemia
  • Large granular lymphocyte disorders
  • Leukaemia: A form of blood cancer in which white blood cells multiply abnormally and circulate through the blood. The abnormal white blood cells make falling ill from infections easier than normal.
  • Leukopenia: Abnormally low numbers of white blood cells in the blood. Leukopenia can result in difficulty fighting infections.
  • Low blood counts (white count, red cell count, or platelet count) due to a drug reaction – for example, heparin-induced thrombocytopenia.
  • Low blood counts not due to medications but related to underlying medical conditions – for example, anaemia of chronic disease or low platelet count secondary to liver disease.
  • Lymphocyte disorders
  • Lymphoma: A form of blood cancer in which white blood cells multiply abnormally inside lymph nodes and other tissues. The enlarging tissues, and disruption of the blood’s functions, can eventually cause organ failure.
  • Lymphoma-Hodgkin’s disease
  • Lymphoma-non-Hodgkin’s
  • Macroglobulinemia
  • Malaria: Infection of red blood cells by Plasmodium, a parasite transmitted by mosquitos. Malaria causes episodic fevers, chills, and potentially organ damage.
  • Monoclonal Gammopathy of Undetermined Significance (“MGUS”), a disorder of plasma cells causing abnormal proteins in the blood)
  • Multiple myeloma: A form of blood cancer of plasma cells similar to leukaemia. Anaemia, kidney failure and high blood calcium levels are common in multiple myeloma.
  • Myelodysplastic syndromes
  • Myelofibrosis
  • Myeloproliferative diseases (characterised by excessive production of blood cells in the bone marrow)
  • Myeloproliferative disorders
  • Myocardial infarction (MI): Commonly called a heart attack, a myocardial infarction occurs when a sudden blood clot develops in one of the coronary arteries, which supply blood to the heart.
  • Natural killer cell leukaemia
  • Non-Hodgkin’s lymphoma
  • Osteosclerotic myeloma
  • Paroxysmal nocturnal hemoglobinuria
  • Pediatric white blood cell disorders
  • Plasma cell disorders
  • POEMS syndrome
  • Polycythemia vera
  • Polycythemia vera-too many red cells
  • Polycythemia: Abnormally high numbers of red blood cells in the blood. Polycythemia can result from low blood oxygen levels or may occur as a cancer-like condition.
  • Primary myelofibrosis-excess fibrous or scar tissue in the marrow
  • Recurrent blood clots (thrombophilia)
  • Sickle cell anaemia
  • Sickle cell disease: A genetic condition in which red blood cells periodically lose their proper shape (appearing like sickles rather than discs). The deformed blood cells deposit in tissues, causing pain and organ damage.
  • Systemic capillary leak syndrome
  • Systemic mastocytosis
  • Thalassemia
  • Thrombocytopenia(low platelet count): Abnormally low numbers of platelets in the blood. Severe thrombocytopenia may lead to bleeding.
  • Thrombocytosis
  • Vitamin deficiency anaemia
  • Von Willebrand disease
  • Waldenström macroglobulinemia
  • White blood cell disorders
Specific Abnormalities

Angiodysplasia is an abnormality in the blood vessels in the gastrointestinal (GI) tract. The GI tract includes the mouth, oesophagus, small and large intestines, stomach, and anus. This condition causes swollen or enlarged blood vessels, as well as the formation of bleeding lesions in the colon and stomach. The type of Angiodysplasia is based on the location of the blood vessel enlargement. A doctor may classify it as either colon Angiodysplasia (enlargement of blood vessels in the colon) or stomach Angiodysplasia (enlargement of blood vessels in the stomach). In addition, this condition can be broken down into the following categories based on location:

  • Colonic and gastric Angiodysplasia
  • Angiodysplasia of the stomach and the intestine
  • Cecal Angiodysplasia
  • Duodenal and small bowel Angiodysplasia

Janus Kinase 2 (Jak-2) [mutation] positive myeloproliferative neoplasms
Myeloproliferative disorders (MPD) cause blood cells to grow abnormally in the bone marrow: too many platelets are being made. The type of MPD depends on which type of cell your body is overproducing. MPD mostly affects one type of blood cell more than the others, but it sometimes can involve two or more.

JAK2 gene fusions with the TEL(ETV6) (TEL-JAK2) and PCM1 genes have been found in leukaemia patients – particularly clonal eosinophilia forms of the disease.[17]

Thrombocytosis (High Platelets)[18]
Thrombocytosis is an increase in platelets > 600 x 109/L, commonly found incidentally in a routine blood test.

There are broadly two types of thrombocytosis:

  • Primary haematological disease:
  • primary thrombocytosis (also referred to as essential thrombocytosis or essential thrombocythemia). The clinical features can relate to an increased incidence of arterial and venous thrombosis and bleeding. Most can remain well for decades.
  • polycythaemia vera
  • primary myelofibrosis
  • chronic myeloid leukaemia
  • myelodysplastic syndromes
  • Secondary or reactive (changes are caused by an exaggerated physiologic response to a primary problem):
  • infectious diseases
  • inflammatory disease
  • neoplasms
  • non-malignant haematological conditions such as acute blood loss, iron deficiency anaemia
  • functional and surgical hyposplenism
  • tissue damage – such as recent trauma or surgery
  • exercise
  • reaction to medications such as steroids, adrenalin, low molecular weight heparins
  • pregnancy
  • allergic reactions

Essential Thrombocythaemia (ET)[19]
Essential thrombocythaemia (ET) is also known as primary thrombocythaemia. This is one of a group of conditions known as myeloproliferative diseases (MPDs).

Myeloproliferative diseases (MPDs)
MPDs are a group of conditions that affect how the bone marrow works. In MPDs, the bone marrow makes too many of one or more types of blood cells.

The main types of MPD are:

  • Essential Thrombocythaemia
  • Polycythaemia Vera
  • Myelofibrosis

Some people with essential thrombocythaemia develop myelofibrosis – a condition in which the bone marrow becomes scarred. People with MPDs rarely develop leukaemia. Myeloproliferative disorders are slow-acting and don’t always cause life-threatening symptoms. The complications of these conditions, however, may be serious. Some complications include enlargement of the spleen and liver.

Essential thrombocythaemia
Essential thrombocythaemia is a rare condition affecting the bone marrow in which too many platelets are made. It is a rare condition that can affect people at any age, including children, but it’s most common in people over 50. ET usually develops very slowly, and for most people, it doesn’t affect their normal life span.

Signs and symptoms of essential thrombocythaemia
Having too many platelets in the blood may not cause any symptoms, and many people with ET are diagnosed during a routine blood test when they have no symptoms. Possible symptoms include:

  • Headaches.
  • Dizziness.
  • Itchy skin.
  • Tiredness (fatigue).
  • Redness, swelling or pain in the hands or feet due to reduced blood flow in those areas.

Sometimes symptoms develop due to complications of ET, such as a blood clot or abnormal bleeding. Too many platelets in the blood can cause clots to form. Less commonly, people may have abnormal bleeding because the platelets in their blood don’t work properly.

Blood clots
Symptoms can occur because a blood clot (thrombosis) has formed in a vein in the body. Clotting problems are more common in people over 60, in people who have had a blood clot before, and in people who have conditions such as high blood pressure or diabetes.

Symptoms of a blood clot depend on where it is in the body. These are some common sites where a clot may form:

  • The deep veins of the leg. Known as deep vein thrombosis or DVT, it can cause pain, swelling, heat and redness, especially in the calf.
  • The brain – This may cause mild symptoms such as headaches, blurred or double vision, or dizziness. Blood clots in the brain may also cause a stroke or mini-stroke (also called a TIA[20]). Symptoms of a stroke or TIA may include weakness, numbness or pins and needles in part of the body, or difficulties with speech or swallowing.
  • The heart – a blood clot in the heart may cause chest pain and, in severe cases, can result in a heart attack.
  • The lungs – a blood clot in a lung may cause breathlessness and chest pain. It is known as a pulmonary embolism.

Abnormal bleeding
Abnormal bleeding is a less common complication than blood clots. It can cause:

  • nosebleeds
  • bruising
  • abnormal vaginal bleeding
  • bleeding gums.

Diagnosis of essential thrombocythaemia (ET)
ET is usually diagnosed by a haematologist (a specialist in blood disorders). The diagnosis may be suspected after the results of a blood test called a full blood count (FBC). This test counts the number of red blood cells, white blood cells and platelets. In ET, there will be a high platelet count. Other conditions can cause an increase in platelet count, such as an infection, arthritis, chronic bleeding or a lack of iron in the blood. These need to be ruled out before a diagnosis of ET can be made.

Tests and investigations that may be done to confirm a diagnosis of ET are:

  • JAK2 blood test: JAK2 is an important gene in regulating blood cell production. If a change (mutation) happens in this gene, it can cause ET. About half of all people with ET have a mutation in the JAK2 gene. This change in the gene happens during the person’s lifetime. It isn’t something you’re born with, and you can’t pass it on to your children.
  • Bone marrow sample (biopsy): Your specialist may want to take a sample of marrow (biopsy) to be checked. The sample is usually taken from the back of your hip bone (pelvis). You’ll be given a local anaesthetic injection to numb the area. The doctor will then pass a needle through the skin into the bone, and draw a small sample of liquid marrow (called a bone marrow aspirate) into a syringe. After this, the doctor will take a small core of marrow from the bone (a trephine biopsy). Both samples will be looked at later under a microscope. The test can be done on the ward or in the outpatient’s department. The whole procedure takes about 15 minutes. It may be uncomfortable when the marrow is drawn into the syringe, but this should only last for a few seconds. You may feel bruised and have an ache for a few days after the test. The discomfort can be eased with mild painkillers.

Treatment for Essential Thrombocythaemia (ET)

  • Treatment aims to reduce the risk of complications, particularly blood clots. If treatment is successful, the outlook for someone with ET can be very similar to that of someone of the same age who doesn’t have the condition.
  • Aspirin is often used as it can reduce the ability of platelets to ‘stick’ together. It doesn’t affect the platelet count but can help lower the risk of blood clots. Side effects of aspirin include an increased risk of bleeding and ulcers in the stomach. If you need to take a painkiller when taking aspirin, ask your doctor what they advise. Some types of painkillers called NSAIDs (non-steroidal anti-inflammatory drugs), such as ibuprofen, may not be right for you.
  • Cytoreductive Therapy[21] (treatment to reduce platelet numbers). If you have a lower risk of developing complications such as blood clots, you may not need treatment other than aspirin. You will be seen by your doctor, who will monitor your condition with regular blood tests. If you are at high risk of blood clots, you’ll usually be started on treatment to reduce the numbers of platelets in your blood.
  • Chemotherapy: This is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. It may be given to try to reduce the platelet count. Hydroxycarbamide is the most commonly used chemotherapy drug to treat ET and is taken as a tablet. It can cause side effects (see page 8), but generally, these are mild. Side effects can include lowered resistance to infection, reduced red blood cell numbers (anaemia), diarrhoea or constipation. Hydroxycarbamide may also affect fertility. People taking it are advised not to get pregnant or father a child, as there may be a risk of harming the developing baby. It’s advisable to use effective contraception while taking the drug and also for a few months afterwards. If Hydroxycarbamide is used in combination with other chemotherapy drugs over a long period, it may increase the chance of the ET developing into leukaemia.
  • The chemotherapy drug busulphan may also be used. Busulfan is usually given as a tablet, but it can be given as an injection into a vein. It can cause similar side effects to Hydroxycarbamide.
  • Interferon-alpha: Interferon is a protein that occurs naturally in the body. It can also be made as a medicine. It slows down the production of blood cells, including platelets. It’s most often used to treat ET in younger people (under 40), although it can be used at any age. Interferon is given as an injection under the skin. Possible side effects include flu-like symptoms, headaches, dizziness and tiredness.
  • Anagrelide: This drug reduces the number of platelets in the blood. It’s taken as a capsule. Side effects can include headaches and palpitations (the sensation of a fast heartbeat). It doesn’t seem to affect fertility, but anagrelide should never be taken during pregnancy or if you are planning to get pregnant. It’s important to use effective contraception when taking anagrelide. Anagrelide is usually given when other treatments have already been tried. Some studies suggest it may increase the chance of changes in the bone marrow that may develop into Myelofibrosis.
  • Radioactive Phosphorus (32P): This may be used to treat ET and is given as an injection into a vein. It irradiates the bone marrow and can lower the number of platelets being produced. The effects of a single injection can last from months to years. Treatment with radioactive phosphorus over many years can cause an increased risk of leukaemia. Your specialist, doctor, or nurse will explain your treatment to you and answer any of your questions.
  • Clinical trials for Essential Thrombocythaemia: New treatments for ET are being researched all the time. Your GP may invite you to participate in a clinical trial to compare a new treatment against the best available standard treatment. Your GP must discuss the treatment with you and have your informed consent before entering you into a trial. Before any trial is allowed to take place, it must be approved by a research ethics committee, which protects the interests of those taking part. If you decide to participate, you can withdraw from the trial at any time. You will then receive the best standard treatment available.

Monitoring for Essential Thrombocythaemia
Your treatment may continue for several years, and you will need to have regular check-ups and blood tests. If you have any problems or notice any new symptoms between these times, let your nurse or doctor know as soon as possible.

Living with Essential Thrombocythaemia
In addition to the treatments and check-ups recommended by your haematologist, you may want to look at additional ways of optimising your health and feeling the best you can. Doing things like following a healthy diet, drinking plenty of fluids, staying active and giving up smoking are good for your general health. These steps can also help reduce the risk of complications such as blood clots. Your doctor or specialist nurse can give you information and support that fits your individual situation.

You may find it helpful to talk things over with family and friends or your doctor or nurse. You can also contact Macmillan cancer support specialists (on 0808 808 00 00) or the organisations at the foot of this page for more information and support.

Example of Treatment
Hydroxycarbamide (aka hydroxyurea) is a medication used in sickle-cell disease, essential thrombocythemia, chronic myelogenous leukaemia and cervical cancer. In sickle-cell disease, it increases foetal haemoglobin and decreases the number of attacks. It is taken by mouth.[22] Hydroxycarbamide is to be taken three times a week to start. There is detailed information about this medication at The side-effects[23] of Hydroxycarbamide are:

Common or very common
Alopecia; anaemia; appetite decreased; asthenia; bone marrow disorders; chills; constipation; cutaneous vasculitis; dermatomyositis; diarrhoea; disorientation; dizziness; drowsiness; dyspnoea; dysuria; fever; gastrointestinal discomfort; haemorrhage; hallucination; headache; hepatic disorders; leucopenia; malaise; mucositis; nail discolouration; nail disorder; nausea; neoplasms; neutropenia; oral disorders; pancreatitis; peripheral neuropathy; pulmonary oedema; red blood cell abnormalities; respiratory disorders; seizure; skin reactions; skin ulcers; sperm abnormalities; thrombocytopenia; vomiting.

Rare or very rare
Cutaneous lupus erythematosus; gangrene; systemic lupus erythematosus (SLE).

Frequency not known
Amenorrhoea; gastrointestinal disorders; hypomagnesaemia; Parvovirus B19 infection; vitamin D deficiency; weight increased.

There are alternative medications, as mentioned in this paper. Hydroxycarbamide is one of a group of chemotherapy drugs known as anti-metabolites, which stop cells from making and repairing DNA. Cancer cells need to make and repair DNA to grow and multiply.

More Information and Support
  • Leukaemia CARE is a national group promoting the welfare of people with leukaemia and other blood disorders. It has regional support groups.
  • MPN Voice The volunteers, MPN patients and healthcare professionals who run MPN provide a source of professionally backed information, facilitate an MPN community and advocate for patients affected by this rare group of blood cancers. Myeloproliferative neoplasms (MPNs) were formerly known as myeloproliferative disorders (MPDs). MPN Voice is registered as a Charity under the auspices of Guy’s and St Thomas’ Foundation.
  • American Society of Hematology (ASH)
  • Hemostasis and Thrombosis Research Society (HTRS)
  • International Society on Thrombosis and Haemostasis (ISTH)
  • European Association for Haemophilia and Allied Disorders (EAHAD)
  • Sickle Cell Society

Interesting Facts about Blood[24]

  • The word “blood” appears at least once in every play by William Shakespeare.
  • Not every creature has red blood. Spiders, lobsters, crabs and snails have blue blood due to the presence of the protein haemocyanin (it contains copper). Earthworms and leeches have green blood. Many invertebrates, such as starfish, have clear or yellowish blood. Some species of marine worms have violet blood. The colour of blood is determined by the type of respiratory pigment used to transport oxygen via the circulatory system to cells.
  • Cows have 800 (and possibly more) blood types.
  • The amount of blood in a pregnant mother’s body will have increased by 50% by the 20th week of pregnancy.
  • Human blood contains around 0.2 milligrams of gold.
  • Some Japanese people believe that blood type is an indicator of a person’s personality. There are even novelty goods themed after blood types.
  • Research has shown that mosquitoes prefer blood type O.
  • There are 150 billion red blood cells in one ounce of blood and 2.4 trillion red blood cells in one pint of blood.
  • The human body manufactures 17 million red blood cells per second. In the event of stress, the body can produce up to seven times that amount (up to 119 million red blood cells per second.)
  • A red blood cell is around seven microns in size (a micron is one-millionth of a metre).
  • It takes just 20 to 60 seconds for a drop of blood to travel from the heart, through your body, and back to the heart again.
  • Nearly 7% of the body weight of a human is made up of blood.
  • An adult body has 100,000 kilometres or 62,000 miles of blood vessels running throughout the body.
  • The average volume of blood present in an adult male body is 5.6 litres, while an adult female body contains 4.5 litres of blood. A newborn baby will have around one cup of blood in its body (234 millilitres of blood).
  • AB0 isn’t the only blood grouping system. The International Society of Blood Transfusion currently recognises 39 systems.
  • Rhnull (rhesus factor zero) is the rarest blood type in the world.
  • About 95% of the body’s blood cells are produced in the bone marrow
  • The only place where blood cannot be found in the human body is the cornea (eye) because it can directly extract oxygen from the air.
  • The supply of blood in blood vessels located in the nose increases when someone catches a cold. This increase happens to keep the nose warm. As a result, blood vessels dilate and increase mucus production, thereby causing a runny nose.
  • More than 400 gallons of blood are filtered by our kidneys every day.
  • Nearly 1/4th of the cells in the human body are red blood cells. In an adult human body, it’s estimated that there are 20-30 trillion red blood cells. The total number of white blood cells in an adult human body is between 4,000 and 11,000.
  • Nearly two million red blood cells in an adult human body die every second. Fortunately, they are replaced by new cells produced in the bone marrow.
  • The human heart pumps between 1 million and 1.5 million barrels of blood during a lifetime.
  • At age 13, an Australian named James Harrison needed 13 litres of blood for major surgery. After he turned 18, he started donating blood. It was found that his blood contained a very rare antigen that was capable of curing Rhesus disease. To date, Harrison has donated blood 1,000 times (over 60 years) and is responsible for saving over two million babies from that disease.
  • The vampire bat has an enzyme that prevents its victims’ blood from clotting on wounds. As a result, the victims lose more blood for the vampire bats.
  • Gnats are especially attracted by people with blood type O.
  • Kidneys regulate the production of red blood cells in the human body. Kidneys are responsible for producing erythropoietin hormone (EPO) that binds with the receptors in stem cell walls in the bone marrow, and after a complex set of events, the DNA of stem cells are transformed into red blood cells.
  • Kidneys will release EPO only when it finds that oxygen levels in the blood have fallen below normal levels. Thus, kidneys are responsible for measuring oxygen levels in the blood.
  • The A positive blood type is the second most common blood type, present in 1 out of 3 people (approximately 35.7% of the population has A positive blood). However, not all ethnic groups share the same proportions of A positive blood types.
  • Saddam Hussein had a Koran, written in his own blood.
Sources and Further Reading

Caution: No advice is implied or given in articles published by us. This guide is for general interest only and is compiled from the sources stated but has not been medically reviewed. It should never be used as a substitute for obtaining advice from your Doctor, a consultant Haematologist or other qualified clinician/medical practitioner. If you have already been given dietary advice you should not make changes without first talking to your GP, consultant or dietitian. The medications mentioned include names for US drugs. The facts are believed to be correct as at the date of publication, but there may be certain errors and omissions for which we cannot be responsible. The information contained in this paper is provided for informational purposes only. There is no implied endorsement or promotion by the writer of any organisation. The hyperlinks were valid at the date of publication.

Picture Credit: “Blood donation” by Canadian Blood Services is licensed under CC BY-NC 2.0

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  2. Source:

  3. Source:

  4. Attribution:

  5. Source and Acknowledgement: © NHS material is Crown copyright.

  6. Cytoplasm is the gelatinous liquid that fills the inside of a cell. It is composed of water, salts, and various organic molecules. Some intracellular organelles, such the nucleus and mitochondria, are enclosed by membranes that separate them from the cytoplasm. Source:

  7. See:

  8. Source: D’Alessandro, Angelo (2017). “Red blood cell proteomics update: is there more to discover?”. Blood Transfusion. 15 (2): 182–87. doi:10.2450/2017.0293-16. PMC 5336341. PMID 28263177.

  9. For an explanation of the capilliary network, see:

  10. Source: Erich Sackmann, Biological Membranes Architecture and Function., Handbook of Biological Physics, (ed. R.Lipowsky and E.Sackmann, vol.1, Elsevier, 1995.

  11. This paragraph is sourced from:

  12. At:

  13. Chronic obstructive pulmonary disease (COPD) is the name for a group of lung conditions that cause breathing difficulties. Source:

  14. Sources:, and

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  16. NOTE: The list of conditions may not be complete and it does not differentiate as to severity. In some cases, hyperlinks are provided where readers can look up details of the condition. There may be some conditions that are dupicated through use of alternative names In all cases, if you are concerned, you should speak to your Doctor, a consultant Haematologist or other qualified clinician/medical practitioner.

  17. Sources: (1) Lacronique V, Boureux A, Valle VD, Poirel H, Quang CT, Mauchauffé M, Berthou C, Lessard M, Berger R, Ghysdael J, Bernard OA (November 1997). “A TEL-JAK2 fusion protein with constitutive kinase activity in human leukemia”. Science. 278 (5341): 1309–12. Bibcode:1997Sci…278.1309L. doi:10.1126/science.278.5341.1309. PMID 9360930, (2) Reiter A, Walz C, Watmore A, Schoch C, Blau I, Schlegelberger B, Berger U, Telford N, Aruliah S, Yin JA, Vanstraelen D, Barker HF, Taylor PC, O’Driscoll A, Benedetti F, Rudolph C, Kolb HJ, Hochhaus A, Hehlmann R, Chase A, Cross NC (April 2005). “The t(8;9)(p22;p24) is a recurrent abnormality in chronic and acute leukemia that fuses PCM1 to JAK2”. Cancer Research. 65 (7): 2662–7. doi:10.1158/0008-5472.CAN-04-4263. PMID 15805263, and (3) Reiter A, Gotlib J (2017). “Myeloid neoplasms with eosinophilia”. Blood. 129 (6): 704–714. All cited at:

  18. Source and Acknowledgement: © NHS material is Crown copyright.

  19. Source and Acknowledgement: © NHS material is Crown copyright.

  20. TIA: A transient ischaemic attack (TIA)

  21. Cytoreductive surgery is a surgical procedure that aims to reduce the amount of cancer cells in the abdominal cavity for patients with tumours that have spread intraabdominally. It is often used to treat ovarian cancer but can also be used for other abdominal malignancies. Sources:

  22. Source:

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  24. Sources:,, and

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