Platelets

Some laboratories use 150 to 450; it is a little lower in pregnancy and in older men; use the range your lab printed.

Platelets are tiny cell fragments made in the bone marrow that plug damaged blood vessels and start the clotting process. The count is the number of them in a given volume of blood. Too few can mean easier bruising or bleeding; too many are usually a reaction to something else going on.

It is part of the full blood count. Doctors look at it when someone bruises or bleeds easily, before operations, during infections and inflammatory illnesses, when monitoring medicines that can lower it, and when looking into blood and bone marrow conditions.

• Infection and inflammation from any cause
• Low iron
• After blood loss or surgery
• After the spleen has been removed
• Some cancers
• Some bone marrow conditions where too many platelets are made

• Viral infections
• Some medicines, including heparin, some antibiotics, chemotherapy and some used for epilepsy and arthritis
• Alcohol
• Liver disease and an enlarged spleen
• Autoimmune conditions where antibodies remove platelets
• Low vitamin B12 or folate
• Pregnancy, slightly
• Bone marrow conditions

• Platelets can clump in the tube, making the count read falsely low; the laboratory usually comments and a repeat in a different tube sorts it out
• A rise during and after an infection or an operation is expected and settles
• Heavy drinking in the days before the test lowers it
• It is a little lower in the general population in pregnancy

No fasting needed. A low count on a single sample is often repeated in a citrate tube to exclude clumping. The trend matters more than one value.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.