Vitamin
Methylcobalamin (Vitamin B12)
Tablet or injection
Quick Summary
Vitamin B12 is needed for healthy nerves and red blood cells.
Vitamin B12 deficiency
Nerve problems
Medical Uses
Vitamin B12 deficiency: Treatment.
Nerve problems: Linked to deficiency.
How it's taken
Take as directed; injections are used for absorption problems.
Your doctor decides the right dose for you and how long to take it.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Few side effects
Usually well tolerated.
Nausea
Rarely.
Rash
Rarely.
Interactions
Metformin and acid reducers
Lower B12 levels over time.
Critical Warnings
Find the cause
Testing helps decide tablets or injections.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Cyanocobalamin (Vitamin B12): drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine