• Normal: 150-400 x 10^9/L
  • Thrombocytopenia: PLT <150
  • <100: risk of surgical bleeding in high risk surgical patients (i.e. neurosurgery, major cardiac, orthopaedic surgery)
  • <50: risk of surgical bleeding
  • <10-20: risk of severe spontaneous bleeding


  • Post-operative consumption (platelets are being used to help heal wounds post-op)
  • Infections (e.g. HIV, hepatitis C, sepsis with disseminated intravascular coagulation)
    • Thrombocytopenia: independent risk factor for morality in the ICU (sepsis)
  • HIT Type I: not ab mediated (direct effect of heparin) and fall in PLTs (nadir: 100) typically resolves with continued heparin administration
  • HIT Type II: ab-mediated (nadir >20) and may lead to thrombosis until heparin is discontinued
  • Other drug causes: quinine, sulfonamides, acetaminophen, cimetidine, ibuprofen, naproxen, ampicillin, piperacillin, vancomycin, glycoprotein IIb/IIIa inhibitors
  • Nutrient deficiencies (e.g. vitamin B12, folate, copper)
  • Pregnancy

Platelets: also an acute phase reactant (increase in inflammation/infection/trauma)