What are platelets?

Platelets are tiny cells which circulate in the blood and whose function is to take part in the clotting process. Inside each platelet are many granules, containing compounds that enhance the ability of platelets to stick to each other and also to the surface of a damaged blood vessel wall.

The platelet count in the circulating blood is normally between 150 and 400 million per millilitre of blood (x109/L).

Newborn babies have a slightly lower level, but are normally within the adult range by three months of age.

Many factors can influence an individual's platelet count including exercise and racial origin. The average life span of a platelet in the blood is approximately 10 days.

What do platelets do?

Platelets are essential in the formation of blood clots to prevent haemorrhage - bleeding from a ruptured blood vessel. An adequate number of normally functioning platelets is also needed to prevent leakage of red blood cells from apparently uninjured vessels.