How long does thrombocytopenia last?

Depends. Thrombocytopenia means low platelet count. It is an abnormal lab- like a symptom, not a disease. There are many reasons for it and "how long it lasts" depends on the cause. It can be from toxic exposure (examples= radiation, alcohol, or drugs), an immune problem ("ITP"), from infections or from bone marrow dysfunction. It can be from Leukemia or from treatment of Leukemia. NEED MORE INFORMATION.