Vitamin B12 deficiency anaemia (pernicious anaemia)

Macrocytic hyperchromic anaemia caused by impaired vitamin B12 absorption. The most common cause is autoimmune atrophic gastritis with anti-intrinsic factor antibodies. Also develops after ileal resection, with long-term proton pump inhibitors or metformin, and in vegans.

ICD-10 D511 drug

Also known as: Pernicious anaemia, Megaloblastic anaemia, Addison-Biermer disease

Drugs used for this condition

ACyanocobalaminFirst line · Vitamins. Haemopoietic stimulantsCyanocobalamin or hydroxocobalamin is first-line for B12 deficiency anaemia. Standard regimen for pernicious anaemia: 1,000 µg intramuscularly daily for 1 week, weekly for 4 weeks, then monthly for life. Oral therapy uses 1,000–2,000 µg daily; the 2018 Cochrane review showed comparable efficacy of oral and parenteral routes at high oral doses. International haematology societies (BSH 2014) recognise both routes.

How to read tiers A–F

Evidence tiers belong to the drug-indication pair, not to the drug as a whole: the same substance can be A for one condition and F for another.

AStrong evidence – first or second line in international guidelines
BRecommended in selected cases
CStudy data contradict each other
DBenefit not proven, no documented harm
FDocumented harm, or risk without benefit