Cyanocobalamin
No prescription neededVitamins and minerals
Comes as:TabletInjection
Usual adult dose
For vitamin B12 deficiency, dose is set by your doctor: often 1 mg (1,000 micrograms) by injection into the muscle several times in the first weeks, then every 1 to 3 months. Tablets: 50 to 1,000 micrograms a day as advised.
Your doctor may give you a different dose. Children's doses depend on weight.
Side effects
Common
- pain at the injection site
- mild diarrhoea
- itching
Serious — get help
Stop taking it and see a doctor straight away if you notice:
- severe allergic reaction after injection (swelling
- difficulty breathing)
Do not take it, or take care, if
- Allergy to cobalt or vitamin B12
- Leber eye disease (a rare inherited eye condition)
Interactions
Medicines that can react with this one.
Minor2 medicinesUsually not a problem, but tell your doctor.
- Metformin
Long-term metformin can lower vitamin B12 levels; B12 may need checking.
- Omeprazole
Long-term use of omeprazole can reduce vitamin B12 absorption from food.