What initial investigations should I perform to confirm a diagnosis of

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

To confirm a diagnosis of iron deficiency anaemia in adults, initial investigations involve assessing haemoglobin levels and iron status.

Full blood count (FBC): This is performed to determine haemoglobin levels and identify the presence of anaemia ,.
Iron status tests: These tests are crucial for confirming iron deficiency. While the provided guidelines detail these tests primarily in the context of chronic kidney disease (CKD), they are generally used to diagnose iron deficiency .
- Percentage of hypochromic red blood cells (% HRC): A result of more than 6% suggests iron deficiency, provided the blood sample can be processed within 6 hours .
- Reticulocyte Hb content (CHr): If % HRC is not feasible, CHr (less than 29 pg) or equivalent tests can be used .
- Transferrin saturation and serum ferritin measurement: If % HRC or CHr tests are unavailable, or if the person has thalassaemia or thalassaemia trait, a combination of transferrin saturation (less than 20%) and serum ferritin (less than 100 micrograms/litre) should be used . It is important not to request transferrin saturation or serum ferritin measurement alone to assess iron deficiency status .

What initial investigations should I perform to confirm a diagnosis of iron deficiency anaemia in adults?