Too few
Thrombocytopenia
Nonfunctional
Aspirin
Von Willebrand disease
Thrombocytopenia
Aspirin
Von Willebrand disease
Acquired (Drug Related)
Warfarin (Coumadin)
Unfractionated heparin
Low molecular weight heparin (i.e. enoxaparin (Lovenox), dalteparin)
Factor Xa Inhibitors (e.g. rivaroxaban, apixaban, fondaparinux, edoxaban)
Direct thrombin inhibitors (e.g. dabigatran, argatroban, bivalirudin)
Illness induced
Vitamin K deficiency
Disseminated Intravascular Coagulation (DIC)
Liver disease induced<unk> Uremic bleeding syndrome
Genetic
Hemophilia
Factor VIII inhibitor
Lupus anticoagulant
Warfarin (Coumadin)
Unfractionated heparin
Low molecular weight heparin (i.e. enoxaparin (Lovenox), dalteparin)
Factor Xa Inhibitors (e.g. rivaroxaban, apixaban, fondaparinux, edoxaban)
Direct thrombin inhibitors (e.g. dabigatran, argatroban, bivalirudin)
Vitamin K deficiency
Disseminated Intravascular Coagulation (DIC)
Liver disease induced<unk> Uremic bleeding syndrome
Hemophilia
Factor VIII inhibitor
Lupus anticoagulant
Disseminated Intravascular Coagulation (DIC)
Factor V Leiden
Nephrotic syndrome
Coagulopathy 
Too few
Bacteremia
Thrombocytopenia
Pancytopenia
Nonfunctional
Anemia
Aspirin