A young woman with microcytic anaemia (MCV 73), a mildly raised platelet count and no organomegaly most likely has iron deficiency with reactive thrombocytosis. Iron studies (ferritin, TIBC) are the initial test for microcytic anaemia.

• JAK2 testing for a myeloproliferative cause is considered only after secondary causes such as iron deficiency are excluded.
• Bone marrow biopsy is rarely necessary.
• Thyroid function is not a workup for microcytosis.