What is anaemia?
Anaemia is defined as haemoglobin below the normal range for sex and age: below 13.5 g/dL in adult men, below 12.0 g/dL in adult women, and below 11.0 g/dL in pregnant women. It affects approximately 1.6 billion people globally — making it one of the most common medical conditions. The cause determines the treatment, which is why a systematic approach using blood tests is essential.
Step 1: CBC + blood film — classifying anaemia by red cell size
| MCV (mean cell volume) | Red cell appearance | Likely cause |
|---|
| Low MCV (<80 fL) | Microcytic (small cells) | Iron deficiency (most common), thalassaemia, sideroblastic anaemia |
| Normal MCV (80–100 fL) | Normocytic (normal size) | Anaemia of chronic disease, haemolysis, blood loss (acute), kidney disease |
| High MCV (>100 fL) | Macrocytic (large cells) | Vitamin B12 deficiency, folate deficiency, alcohol, hypothyroidism, liver disease |
Step 2: Iron deficiency anaemia workup
| Test | Iron deficiency finding |
|---|
| Ferritin | <30 ng/mL (often much lower) — most sensitive marker |
| Serum iron | Low |
| TIBC | High (body compensates by making more transport protein) |
| Transferrin saturation | <16% |
| MCV | Low (<80 fL) |
| Blood film | Microcytic, hypochromic cells; target cells |
Step 3: Megaloblastic anaemia workup
| Test | B12 or folate deficiency finding |
|---|
| Serum B12 | <200 pg/mL (deficiency); <100 (severe) |
| Serum folate | <3.0 ng/mL |
| MCV | >100 fL (macrocytic) |
| Blood film | Oval macrocytes; hypersegmented neutrophils (5+ lobes) |
| Peripheral blood smear | Hypersegmented neutrophils are pathognomonic of megaloblastic anaemia |
Step 4: Haemolytic anaemia workup
| Test | Finding in haemolysis |
|---|
| LDH | Elevated (released from lysed red cells) |
| Indirect bilirubin | Elevated (breakdown product of haemoglobin) |
| Haptoglobin | Low or absent (mops up free haemoglobin; depleted in haemolysis) |
| Reticulocyte count | High (bone marrow compensating) |
| Blood film | Spherocytes (hereditary spherocytosis), sickle cells, fragmented cells (microangiopathy) |
| Direct Coombs test | Positive in autoimmune haemolytic anaemia |
Common treatments by anaemia type
| Type | Treatment |
|---|
| Iron deficiency | Ferrous sulfate oral iron (200 mg 2-3x daily) or IV iron; identify and treat source of blood loss |
| Vitamin B12 deficiency | IM cyanocobalamin/methylcobalamin injections; or high-dose oral B12 (1,000 mcg daily) |
| Folate deficiency | Folic acid 5 mg daily for 4 months; address underlying cause |
| Anaemia of chronic disease | Treat underlying condition; EPO injections for kidney disease-associated anaemia |
| Thalassaemia (minor) | Usually no treatment needed; genetic counselling |
Questions to ask your doctor
- What type of anaemia do I have based on MCV?
- Why am I iron deficient — is there internal bleeding?
- Do I need B12 injections or will tablets work?
- Should I have a haemoglobin electrophoresis for thalassaemia?
- Is my anaemia related to a chronic illness?
Medical Disclaimer: This page is for general educational purposes only and does not constitute medical advice. Always consult a qualified doctor for diagnosis and treatment.