When would I need to get vitamin B12 shots?

You would need to get vitamin B12 shots from your doctor if you have a severe B12 deficiency. A number of things can cause this, including a poor diet, an inability to make a compound needed for your body to use B12 (a condition called pernicious anemia), changes in digestion with aging, medical conditions and, sometimes, interactions with prescription drugs. Whatever the cause, if your B12 levels are particularly low, your doctor may prescribe B12 shots, either daily or weekly, until your levels are normal. After that, you may need to get monthly B12 shots.
Dr. David L. Katz, MD, MPH
Preventive Medicine
For garden-variety B12 deficiency, due to inadequate intake from food or supplements, oral supplementation suffices to fix the problem. But pernicious anemia cannot be treated with oral B12, because the lack of intrinsic factor will prevent absorption. The appropriate treatment is B12 injections your doctor must provide. In some cases, genetic mutations can limit the ability to metabolize B12 as well, in which case you will need to get the active form, called methylcobalamin, instead of the more common cyanocobalamin.

Jill A. Grimes, MD
Family Medicine
You should only get B12 shots if your B12 levels are low. Check with your doctor if you are concerned.

The good news is that B12 is easily replaced, and though it will take a few months to get tanked back up, you should completely recover with time, as long as you are consistent about your method of B12 replacement.

Extra B12 should not be harmful to anyone, as it is a water-soluble vitamin, which means you may have lovely, expensive, bright yellow/green urine if you over-replace, but no other worries.

Many people get B12 shots because, well, they ask for one. There is a myth out there, quite popular with the entertainment industry, that getting a B12 injection gives you a shot of energy. This idea has been around for many decades, and there are people who absolutely swear it works. Additionally, many people believe if they are  stressed and rundown -- say at finals time in college -- then a B12 shot will keep them from getting sick. Is this true?

There are not any current evidence-based medical studies that support this theory. There is one recent study that showed high intake of vitamin B12 (and of B6) was protective against depression in older adults living within the community.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.