(dosing may vary with individuals and with clinicians; doses presented here are examples for injection, not for oral or topical use) : Pernicious anemia (lifetime treatment required): 100 mcg intramuscularly or subcutaneously once daily for 6-7 days, followed by the same dose given on alternate days for seven doses, then every 3-4 days for another 2-3 months. Recommended maintenance dose is 100 mcg monthly for life.
For iron deficiency, the recommended dose is 30 mcg intramuscular injection once daily for 5-10 days then 100 to 200 mcg intramuscular injection monthly.
Chloramphenicol (Chloromycetin) may decrease the effectiveness of cyanocobalamine. Cancer drugs may reduce the response to cyanocobalamine treatment. Use of colchicine (Colcrys) and heavy alcohol intake for longer than 2 weeks may decrease the absorption of vitamin B12.
Vitamin B-12 is a water-soluble vitamin that’s naturally present in some foods like fish, meat, poultry, eggs, milk, and milk products, according to the National Institutes of Health (NIH). It keeps your nerves and blood cells healthy, helps make your body's DNA, and can protect against anemia, which can make you feel tired and weak.
According to the NIH, the daily recommended allowance for vitamin B-12 is 2.4 micrograms for both men and women (it goes up to 2.6 micrograms for pregnant women, and 2.8 micrograms for those who are nursing). JSYK: A double cheeseburger has 2.1 micrograms of vitamin B-12, per the NIH.
A B-12 shot is basically just a large dose of B-12—one shot typically contains 1,000 micrograms of the stuff, says Susan Besser, M.D., a primary care physician at Mercy Medical Center in Baltimore. They’re usually given by a primary-care doctor or nurse, although you can be trained to do it yourself, similar to how people can learn to give themselves insulin, Besser says.
People who are all about these shots claim that they can give you more energy, boost your metabolism, and help you lose weight in the process.