Platelet Count

July 21, 2020

What are platelets?

A platelet count simply tells us how many platelets are in circulation. Platelets are small cell fragments which circulate in the blood alongside red and white cells. Produced in the bone marrow, platelets, have an important role in coagulation (the clotting of blood), they stem bleeding when blood vessels become injured, preventing blood loss.[1]

Why take a platelet count blood test?

A platelet count gives a value for the number of platelets in circulation, it doesn’t give any indication about how well they are functioning. Platelet function tests, however, are used if there is a suspicion that the platelets are not functioning as they should.  A normal platelet count in a healthy adult is between 150 and 450 x 109/L, so there could be up to 450,000 platelets per microlitre of blood in circulation.[1]

What function do platelets have in the body?

Blood contains three main components, red blood cells, white blood cells and platelets. Platelets are also called thrombocytes and their main function is to react to bleeding in the body by sticking together to initiate a blood clot and ultimately, stop the bleeding. They have no nucleus, so are called anucleate cells. Platelets travel in the blood searching for any problems in structural integrity. So, if there is a wound, the platelets will work together to naturally stem the bleeding and clot the blood, preventing blood loss.[2]

Upon the discovery of injury to a blood vessel, platelets interact with the subendothelial matrix. Usually, blood vessels are lined with special cells called endothelial cells. However, when a blood vessel is injured the endothelial cells are lost and the subendothelial matrix is exposed. The matrix sends out strong signals which stimulate platelets to become activated and adhere to each other.[3] The ability of the body to naturally stop the flow of blood is called haemostasis. Abnormalities, however, can cause haemorrhage or blood clots to occur.

Inactivated platelets are circular in shape, however, when they become activated, platelets change to a spiky structure. The change in shape makes it easier for the platelets to stick to both the damaged vessel and to each other to plug the hole. A protein in the blood, fibrin, interacts with the platelets to help seal the wound by forming a net, trapping more activated platelets and red blood cells to seal the wound.

How do changes in platelet count affect health and wellbeing?

A low platelet count is referred to as thrombocytopenia and is classified as having less than 150 x 109/L platelets in circulation. Two things can cause thrombocytopenia, either:

  • the bone marrow is not producing enough platelets, or
  • the bone marrow is producing normal numbers of platelets but they are being destroyed faster than they should be in the blood

A low platelet count can be found in several conditions and the severity will depend upon the presence or absence of bleeding.

An increased platelet count, on the other hand, is classified as having a platelet count above 450 x 109/L and is referred to as thrombocytosis. Thrombocytosis occurs because of an overproduction of platelets by the bone marrow. There are two reasons why this may occur:

  1. bone marrow disorders
  2. a side effect of reactive thrombocytosis

If you are worried about your platelet count or just want to check where you fall on the range, you can test your level with a simple at-home blood test.

What can cause platelet count to change?

A reduced platelet count can be found in:

  • Immune thrombocytopenia where platelets are destroyed faster than they should be because of an immune condition.
  • Vitamin B12 or folate deficiency
  • Infections and viruses
  • Liver disease leukaemia
  • Bone marrow disorders like aplastic anaemia and myelodysplasia

A high platelet count can have serious side effects, such as the development of blood clots. These clots can vary in size, small clots found in the hands and feet can result in numbness, redness and tingling while larger clots can affect organs such as the brain and heart, increasing the risk of strokes and heart attacks. [4]

A high platelet count is sometimes associated with a bone marrow disorder, such as:

  • Essential thrombocythemia
  • Chronic myeloid leukaemia
  • Polycythaemia Vera

However, thrombocytosis can occur because of reactive thrombocytosis, with the most common causes in adults being infection, tissue damage, chronic inflammatory disorders and malignancy.[5]

What are the most common symptoms?

Mild thrombocytopenia often occurs without any symptoms, although they can appear over time. If the condition is severe then it can cause bleeding almost anywhere in the body. A low platelet count can cause external bleeding which can cause purpura (purple, brown and red bruises) or petechiae, small red or purple dots present on the skin.

Other symptoms which suggest external bleeding are:

  • Prolonged bleeding, even if it is just a small cut
  • Abnormal vaginal bleeding
  • Nosebleeds or bleeding gums when you brush your teeth

An infection can cause reactive thrombocytosis. The signs of an infection are:

  • Fever – temperature above 37.5C
  • Skin feeling hot to touch
  • Fatigue
  • Aching muscles
  • Feeling dizzy or confused
  • Feeling cold or shivery
  • Diarrhoea
  • Headache

How to your keep platelet count in the healthy range

There are certain things you can do to help prevent pathogens from entering your body and causing infection. For example, always remember to wash your hands after visiting the lavatory as well as before and after handling food. Equally, keeping yourself hydrated can help to prevent illness. You should aim to drink approximately 2 litres of water per day.

Physical activity prevents cardiovascular morbidity and mortality, but it does lead to a temporary activation of the thrombotic system. In healthy individuals, fibrin activity is increased, but in individuals who have heart disease, their fibrin activity is compromised. Therefore, it is essential to seek medical advice before attempting strenuous physical activity.[6]

Diet has a potential role in the development and progression of cardiovascular disease, especially platelet function. The Mediterranean diet may prevent cardiovascular disease, while foods like ginger, onion, omega-3 fatty acids, tomato and wine can all reduce platelet aggregation.[7]


[1] Lab Tests Online UK. (2014). Platelet Count. Available at:

[2] Walsh, T, G., Metharom, P and Berndt, M, C. (2014). The Functional Role of Platelets in the Regulation of Angiogenesis. Platelets: Early Online.

[3] Watson, S, P. (2009). Platelet Activation by Extracellular Matrix Proteins in Haemostasis and Thrombosis. Current Pharmaceutical Design: 15.

[4] National Heart, Lung, and Blood Institute. (2018). Thrombocythemia and Thrombocytosis. Available at:

[5] Bleeker, J, S and Hogan, W, J. (2011). Thrombocytosis: Diagnostic Evaluation, Thrombotic Risk Stratification, and Risk-Based Management Strategies. Thrombosis.

[6] Yilmaz, M, B., Saricam, E., Biykoglu, S, F., Guray, Y., Guray, U., Sasmaz, H and Korkmaz, S. (2004). Mean Platelet Volume and Exercise Stress Test. J Thromb Thrombolysis: 17(2), pp 115-20.

[7] McEwen, B, J. (2014). The Influence of Diet and Nutrients on Platelet Function. Semin Thromb Hemost: 40(2), pp 214-226.

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This information has been medically reviewed by Dr Nicky Keay

Nicola has extensive clinical and research experience in the fields of endocrinology and sport and exercise medicine. Nicky is a member of the Royal College of Physicians, Honorary Fellow in the Department of Sport and Exercise Sciences at Durham University and former Research Fellow at St. Thomas' Hospital.

Dr Nicky Keay

Dr Nicky Keay

BA, MA (Cantab), MB, BChir, MRCP.