Anaemia

A reduction in haemoglobin concentration, haematocrit, or RBC count.

Aetiology

Decreased RBC production (low reticulocytes, little or no change in RBC morphology)
- Iron deficiency
- Acute and chronic inflammation
- Renal disease
- Hypometabolic states - protein malnutrition and endocrine deficiencies
- Marrow damage
Maturation disorders (slightly to moderately elevated reticulocytes, with microcytosis or macrocytosis)
Decreased survival
- Increased RBC destruction - high reticulocytes >3x normal
- Acute blood loss - reticulocytes up to 2.5x normal

Female - Hb < 119 or haematocrit <35%
Male - Hb <136 or haematocrit <40%
Use same cut-offs for all ethnicities and ages
Lower normal cut-offs in pregnancy - 110 in first trimester, 105 in second and third trimester

Decreased (or inappropriately low)
- Deficiency of iron, B12, folate or copper
- Medications that suppress the bone marrow
- Primary bone marrow disorders (MDS, myelofibrosis, leukaemia)
- Very recent bleeding within 5-7 days, pre-compensation
Increased
- Haemolysis
- Repletion of deficient iron, B12, folate or copper
- Recovery from bleeding

RBC size/ MCV	Reticulocyte count
	Low or normal*	Increased
Microcytic MCV <80 fL	Iron deficiency (late) Anemia of chronic disease/inflammation Sideroblastic anemias	Thalassemia Hemolysis¶
Normocytic MCV 80 to 100 fL	Bleeding (acute) Iron deficiency (early) Anemia of chronic disease/inflammation Bone marrow suppression (cancer, aplastic anemia, infection) Chronic renal insufficiency Hypothyroidism Hypopituitarism Excess alcohol Copper deficiency/zinc poisoning	Bleeding (with bone marrow recovery) Hemolysis¶ Bone marrow recovery (eg, after infection, vitamin B12 or folate replacement, and/or iron replacement)
Macrocytic MCV >100 fL	Vitamin B12 or folate deficiency Excess alcohol Myelodysplastic syndrome Liver disease Hypothyroidism HIV infection Medications that interfere with nuclear maturation (hydroxyurea, methotrexate, some chemotherapy agents)	Hemolysis¶ Bone marrow recovery (eg, after infection, vitamin B12 or folate replacement, and/or iron replacement)