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Anaemia: Types, Causes and How Each Is Treated

Anaemia, a low haemoglobin, can result from iron deficiency, B12 or folate deficiency, chronic disease, or blood disorders. Understanding the type guides targeted treatment.

Written by Suman Konda, PharmD, Clinical Pharmacist · Based on peer-reviewed sources · Editorial policy · Not medical advice

Last updated: · How we check our content

Definition (WHO)
Hb <130 g/L (M); <120 g/L (F)
Most common cause
Iron deficiency anaemia
Affects globally
~2 billion people
Key test
FBC + MCV + reticulocyte count

Anaemia Classification by MCV

MCVTypeCommon Causes
Low (<80 fL) — MicrocyticIron deficiency, thalassaemia, sideroblastic anaemiaCheck ferritin, iron studies, Hb electrophoresis
Normal (80–100 fL): NormocyticAnaemia of chronic disease, acute blood loss, CKD, early combined deficiencyCheck reticulocyte count, CRP, eGFR
High (>100 fL): MacrocyticB12 deficiency, folate deficiency, alcohol, hypothyroidism, drugs (methotrexate)Check B12, folate, TFTs, alcohol history
Anaemia pathway by red cell sizeHow mean cell volume narrows the likely cause of anaemia.Red cell size narrows the cause of anaemiaLow haemoglobinNext: look at MCVMCV < 80 fLMicrocyticIron deficiency,thalassaemia, chronicdiseaseMCV 80–100 fLNormocyticBlood loss, chronicdisease, kidney disease,haemolysisMCV > 100 fLMacrocyticB12 or folate deficiency,alcohol, thyroid, drugsThe reticulocyte count then separates reduced production from increased loss or destruction:low reticulocytes point to a production problem, high to bleeding or haemolysis.
Scroll sideways to see the whole diagram
How mean cell volume and reticulocytes narrow the cause of anaemia.
What the diagram shows. Once anaemia is confirmed, the mean cell volume splits the causes into three groups. Small cells suggest iron deficiency or thalassaemia; normal-sized cells suggest blood loss, chronic disease or kidney disease; large cells suggest B12 or folate deficiency, alcohol or thyroid disease. The reticulocyte count then separates a marrow that is not producing enough cells from one responding normally to bleeding or destruction.

Specific Anaemia Types

TypeMechanismTreatment
Iron deficiencyBlood loss or poor absorptionOral iron (ferrous sulfate); treat cause
B12 deficiencyPernicious anaemia or dietaryIM hydroxocobalamin; oral high-dose B12
Anaemia of chronic diseaseCytokine-mediated iron sequestrationTreat underlying condition; EPO if CKD
Haemolytic anaemiaPremature RBC destruction (autoimmune, hereditary)Folic acid; steroids; treat cause
Aplastic anaemiaBone marrow failure: no cell productionStem cell transplant; immunosuppression
Seek Urgent AssessmentHaemoglobin <70 g/L causes significant symptoms and may require transfusion. New severe anaemia with fatigue, pallor, and breathlessness warrants same-day assessment.
Investigate the Cause, Not Just the AnaemiaTreating iron deficiency without finding the source of blood loss misses bowel cancer, coeliac disease, or peptic ulcer. Always investigate the cause of iron deficiency anaemia in adults, especially post-menopausal women and all men.
What are the symptoms of anaemia?
Fatigue, pallor (pale inner eyelids, nail beds), shortness of breath on exertion, palpitations, dizziness, headache, poor concentration, cold intolerance. Severe anaemia causes angina and heart failure in those with underlying heart disease.
How quickly can anaemia be corrected?
Iron tablets increase haemoglobin by approximately 10–20 g/L per month. B12 injections show response within 2–4 weeks. IV iron works faster than oral. Blood transfusion corrects anaemia within hours.
Can diet alone treat iron deficiency anaemia?
Dietary improvement alone is rarely sufficient to correct established iron deficiency. Supplemental iron (ferrous sulfate 200 mg twice daily) is required, with dietary optimisation alongside. Address the cause of the deficiency.
Does anaemia require blood transfusion?
Most anaemia does not require transfusion. Thresholds vary: most stable patients tolerate Hb >70–80 g/L. Patients with cardiac disease or acute blood loss may need higher thresholds. Transfusion is reserved for symptomatic severe or refractory anaemia.
Vitamin B12B12 deficiency

ICD-10-CM diagnosis codes

Anaemia is coded by its underlying cause rather than by haemoglobin level alone:

ICD-10-CM codeDescription
D50.9Iron deficiency anemia, unspecified
D50.0Iron deficiency anemia secondary to chronic blood loss
D50.8Other iron deficiency anemias
E61.1Iron deficiency (without anemia)
D52.8Other folate deficiency anemias
D51.0Vitamin B12 deficiency anemia due to intrinsic factor deficiency

Codes shown are from the current ICD-10-CM classification (FY2026) and are provided for general reference. Clinical coding is performed by trained coders using the full medical record.

References

The clinical information on this page is based on peer-reviewed sources indexed in PubMed, the biomedical literature database of the US National Library of Medicine.

  1. Rusch JA, van der Westhuizen DJ, Gill RS, Louw VJ. Diagnosing iron deficiency: controversies and novel metrics. Best Pract Res Clin Anaesthesiol. 2023;37(4):451-467. doi:10.1016/j.bpa.2023.11.001 · PMID 39764832
  2. Ford J. Red blood cell morphology. Int J Lab Hematol. 2013;35(3):351-7. doi:10.1111/ijlh.12082 · PMID 23480230
  3. Anemia. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK499994
  4. Anemia Screening. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK499905

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Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.