Last updated:
March 25, 2026
Anaemia is defined as a decrease in red cell mass as evidenced by a haemoglobin concentration below the reference range for a given age or sex in a given population or geographic location. A haemoglobin concentration of <13g/dL in adult males and <12g/dL for adult females constitutes anaemia.
Classification of Anaemia
| Classification | Types | Examples |
|---|---|---|
| Hemorrhage | Acute Loss | Trauma |
| Chronic Loss | Upper and Lower GI bleed, Menorrhagia, Hematuria | |
| Hemolysis | Inherited Hemolytic Anemia | Membranopathies, Enzymopathies, Hemoglobinopathies |
| Acquired Hemolytic Anaemia | Alloimmune, Autoimmune, TTP, HUS, Malaria | |
| Diminished Erythropoiesis | Microcytic Anaemia | Defective heme synthesis, Defective globin chain |
| Macrocytic Anaemia | Megaloblastic and Non-megaloblastic macrocytic anemias |
Causes of anaemia according to morphology
| Morphology | Examples |
|---|---|
| Normocytic anaemia | Acute blood loss, Anaemia of chronic disease, Bone marrow failure, Renal failure, Hypothyroidism, Hemolysis, Pregnancy |
| Macrocytic anemia | B12 and folate deficiency, Alcohol excess, Reticulocytosis, Cytotoxics, Myelodysplastic syndrome, Hypothyroidism |
| Microcytic anemia | Iron deficiency anemia, Thalassemia, Sideroblastic anemia |
- Signs and symptoms
- Fatigue
- Weakness
- Pallor
- Seen on mucous membranes and conjunctivae
- Breathlessness
- Jaundice
- Seen in haemolytic anaemia
- Pica
- Craving for ice (pagophagia) or dirt (geophagia)
- Seen in iron deficiency anaemia
- Features of a hyperdynamic state
- Bounding pulses
- Tachycardia/palpitations
- Flow murmur
- Pulsatile sound in the ear
- Possibly heart failure (anaemia-induced heart failure)
- Features of extramedullary haematopoiesis
- Hepatosplenomegaly
- Paravertebral mass
- Widening of diploic spaces of the skull
- Investigations
- To establish that there is anaemia
- Complete blood count for Hemoglobin and Hematocrit
- To classify the anaemia
- Red cell indices (MCV, MCH, MCHC) and Peripheral blood film
- Size: Normocytic, Microcytic, Macrocytic
- Degree of haemoglobinization: normochromic, hypochromic
- Shape e.g. Poikilocytes
- Red cell indices (MCV, MCH, MCHC) and Peripheral blood film
- To establish the cause of anaemia
- Decreased Erythropoiesis
- Bone marrow aspirate or Trephine Biopsy: for bone marrow failure
- Iron, Folate and B12 levels: for hematinic deficiency
- Excessive loss or destruction
- Urinalysis and Serum study (Bilirubin, Haptoglobin, LDH) for hemolytic anaemia
- Stool for ova and cysts
- Gastroscopy and Colonoscopy
- Decreased Erythropoiesis
- To establish that there is anaemia
- Indications for blood transfusion in anaemia
- Hb < 7 g/dL (especially in acute anemia)
- Symptomatic Anaemia
- Comorbidities, e.g. Ischemic Heart Disease
- Treatment of severe anaemia with heart failure
- Transfuse with caution to restore Hb to safe levels of 6-8 g/dL
- Intravenous or oral furosemide
- Check for signs of worsening congestion (JVP, basal crackles). If present, stop and treat.
