Last edited 10/2019 and last reviewed 12/2022

Thrombocytopaenia is a decrease in the number of platelets in the blood - it reduces the ability of the blood to clot and is thus a bleeding diathesis. It is defined as a platelet count less than 100 x 10^9/L (<100,000 per cubic mm).

In addition, it is important to consider also the causes of apparent thrombocytopaenia - i.e. conditions where there is platelet dysfunction.

Neonatal thrombocytopaenia has a modified differential diagnosis.

A suggested management of low platelet count in adults (1):


  • NHS Camden CCG. Abnormal FBC guidance - for adults (Accessed 30/10/19)