Initial vitamin B₁₂ supplementation in adults

For adults with vitamin B₁₂ deficiency who have severe anaemia or neurological symptoms, give supplementation immediately. For initial therapy use:

For adults without severe anaemia or neurological symptoms, less intensive intramuscular hydroxocobalamin therapy may be used (eg a longer interval between doses, shorter duration of therapy or a lower dosage).

In patients with anaemia, malaise usually improves within 2 days of the first hydroxocobalamin injection, and reticulocyte count peaks at about 7 days. Serum iron concentration can fall after 1 to 2 days; iron supplementation may be required. Also consider if potassium supplementation is needed. Haemoglobin concentration usually increases by about 10 g/L per week.

Neuropathy improves slowly with vitamin B₁₂ therapy. Patients with a long history of neurological symptoms may have residual effects.

Most adults with vitamin B₁₂ deficiency require lifelong maintenance therapy after initial intramuscular therapy.