Indications
Vitamin B12 (cobalamin, available as Cyanocobalamin, Methylcobalamin or Hydroxocobalamin) is used to prevent and treat vitamin B12 deficiency, for example in:
- pernicious anaemia, where the stomach cannot absorb vitamin B12 from food;
- megaloblastic anaemia caused by low vitamin B12;
- people with a low intake, such as strict vegetarians and vegans;
- people with poor absorption after stomach or bowel surgery, or with bowel disease;
- long-term users of Metformin or stomach acid reducers, when levels are low;
- nerve problems such as tingling, numbness or burning (peripheral neuropathy), where the doctor advises it as supportive treatment.
How It Works
Vitamin B12 is needed to make healthy red blood cells, to copy DNA and to keep the nerves working well. When the body has too little, red blood cells become large and fewer in number (anaemia), and nerves can be damaged. Taking Vitamin B12 refills the body’s stores and allows normal blood cell production and nerve repair.
Dosage and Administration
Tablets or capsules, adults: commonly 500 to 1000 mcg a day, or as directed by the doctor or the product label. Some products for nerve problems are taken in divided doses through the day.
Injections (for pernicious anaemia, severe deficiency or poor absorption): given into a muscle by a doctor or nurse. A course of frequent injections is usually given first, followed by a maintenance injection every 1 to 3 months, as prescribed. People with pernicious anaemia usually need treatment for life.
Children: as prescribed. Tablets can be taken with or without food.
Interactions
- Metformin, Omeprazole and other proton pump inhibitors, Ranitidine-type acid reducers, Colchicine and long-term Neomycin can reduce absorption from food.
- Chloramphenicol may reduce the blood response to Vitamin B12.
- Folic Acid can improve the blood picture while hiding an untreated B12 deficiency, so nerve damage can progress; deficiency should be checked before using high-dose Folic Acid alone.
Contraindications
Do not use Vitamin B12 if you are allergic to cobalamin, cobalt or any ingredient of the product. Cyanocobalamin is not used in people with Leber’s disease (an inherited eye nerve condition).
Side Effects
Side effects are uncommon. Some people have mild diarrhoea, nausea, itching, rash, headache or pain at the injection site. Urine may look darker or reddish with Hydroxocobalamin.
Get urgent medical help if you have:
- swelling of the face, lips or throat, wheezing or difficulty breathing (a rare allergic reaction, mostly with injections);
- muscle weakness, cramps or an irregular heartbeat at the start of treatment for severe anaemia (low potassium; the doctor checks blood tests in this situation);
- chest pain or sudden shortness of breath.
Pregnancy and Lactation
Vitamin B12 is needed in pregnancy and breastfeeding, and normal supplement doses are considered safe. Use treatment doses only on a doctor’s advice.
Precautions and Warnings
- The cause of a deficiency should be found before treatment, and a blood test is helpful before starting.
- People with severe anaemia should be monitored at the start of treatment.
- Tell your doctor if you have kidney disease or a history of allergy to injections.
- Do not use Vitamin B12 to treat tiredness or tingling without a doctor’s assessment, as other causes may need attention.
Overdose
Vitamin B12 has very low toxicity, and extra amounts are passed in the urine. If a large amount is taken by mistake and you feel unwell, contact a doctor.
Therapeutic Class
Vitamin; vitamin B complex (cobalamin).
Storage
Store below 30°C in a dry place, away from light. Keep injections in the outer carton to protect from light. Keep out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.