Number of platelets in a cubic millimetre of whole blood – normally 150 000 – 300 000.
Increase (thrombocytosis) polycythemia, thrombocytopenia, neoplasia, iron deficiency anaemia, inflammatory diseases, chronic renal disease
Decrease (thrombocytopenia) acute leukaemia, allergic conditions, liver disease, infection, SLE, thyroid disease, severe iron deficiency anaemia
Lowest safe level for elective surgery is considered 100 000 cell/mm3
Spontaneous bleeding usually occurs below 25 000 – 50 000