Vitamin B12 Injections for Weight Loss: Do They Really Work?

Traditionally used for conditions associated with vitamin B12 deficiency, B12 injections are often marketed to help lose weight, fight fatigue, or boost brain and athletic performance. Are these claims true? If you want to know more about vitamin B12 injections, this article is for you.

Key takeaways:
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    Individuals with vitamin B12 deficiency need to take B12 supplements to treat anemia and other health complications.
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    In the majority of cases, taking B12 in oral form is enough to correct the deficiency.
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    Vitamin B12 injections are available and FDA-approved for some conditions, but can also be used off-label by some healthcare providers.

About vitamin B12

Also known as cobalamin, vitamin B12 is an essential nutrient that plays key roles in brain function, metabolism, and the production of red blood cells. This vitamin also helps make DNA, the genetic material found in all bodily cells.

Animal products, particularly organ meats, eggs, fish, and seafood, are naturally rich in vitamin B12. Some foods, like cereals, are fortified with B12. This vitamin is widely available in health food stores as a capsule, liquid, gummy, or sublingual tablet.

Vitamin B12 is also available in injectable form, delivered either in the muscle (intramuscular) or under the skin (subcutaneous). While B12 injections are approved by the FDA for certain conditions associated with vitamin B12 deficiency, they are often used off-label by naturopaths or other doctors who use vitamin therapy to boost energy levels, improve brain function, or assist with weight loss.

Who is at risk of developing B12 deficiency?

Vitamin B12 deficiency has to be treated promptly to avoid irreversible damage. Vitamin B12 anemia causes fatigue, palpitations, weight loss, infertility, and, in severe cases, dementia. B12 deficiency can also cause numbness and tingling in the hands and feet and depression. If a pregnant or breastfeeding woman has B12 deficiency, the baby is at increased risk for neural tube defect, developmental delays, anemia, and failure to thrive.

Diet is the main source of vitamin B12, and a healthy, balanced diet can provide the appropriate amount of B12. Some people are at increased risk of B12 deficiency and may benefit from supplementation:

Vegans and vegetarians are at high risk because animal products, fish, and seafood are the richest sources of vitamin B12.

Some people may consume enough B12 but do not absorb it properly because there is a two-step process. First, the stomach acid breaks down the vitamin from the proteins attached to it. Then, the vitamin B12 is combined with a compound from the stomach called intrinsic factor, and the body can absorb it. Individuals with pernicious anemia can’t make intrinsic factors and have trouble absorbing vitamin B12 from foods and supplements.

The elderly are at increased risk because the level of stomach acid decreases with age, and the absorption of B12 from foods is also decreased. Between 3% and 43% of older adults in the US have vitamin B12 deficiency.

Individuals who have Crohn’s disease, celiac disease, atrophic gastritis, or other conditions affecting the digestive tract, or those who have had stomach or small bowel surgery, are at increased risk of developing B12 deficiency.

Prolonged use of medications like metformin or acid blockers can deplete the body of B12.

FDA-approved vitamin B12 Injections

A simple blood test can detect B12 deficiency. Many cases of B12 deficiency anemia are mild and can be corrected with vitamin B12 oral supplements. Doctors may recommend vitamin B12 oral supplements during times when B vitamins are required in high amounts, such as pregnancy, certain thyroid diseases, or cancer.

Vitamin B12 injections are approved by the FDA to treat specific conditions. Pernicious anemia, cancer of the pancreas of the bowel, celiac disease, small bowel bacterial overgrowth (SIBO), fish tapeworm infestation, or B12 deficiency after stomach surgery can be corrected with vitamin B12 injection.

Off-label uses of B12 injections

B12 injections are more often used off-label. Off-label refers to prescriptions for a drug that is for a different condition or dosage than what the FDA has approved. Naturopaths and other doctors trained in alternative therapies may recommend B12 injections for the elderly, athletes, vegans, and vegetarians, or for individuals who have depression or sleeping problems. These healthcare providers have special training to administer injections and may offer intravenous (IV) therapy with vitamin C, other B vitamins, minerals, or amino acids in conjunction with B12 injections.

While getting B12 shots is unlikely to harm your health, they may not be necessary. The research does not confirm the benefits of this injection for weight loss, boosting energy, or promoting athletic endurance.

Cautions and warnings

Vitamin B12 injections should not be used in case of allergic reactions to vitamin B12 or cobalt, which is part of the chemical structure of vitamin B12.

Individuals with Leber’s disease (a rare, inherited form of vision loss) should not receive these injections due to the risk of optic nerve damage.

Tell your doctor before getting the injection if you have eye problems, kidney or liver disease, any type of infection, or if you take medication that affects the bone marrow.

The most common side effect associated with B12 injections is diarrhea. Although very rare, there are some documented cases of serious allergic reactions to B12. Emergency treatment should be sought if you develop hives, difficulty breathing or swelling of the face, lips, and throat after a B12 shot.

Vitamin B12 supplements can interact with certain drugs, particularly aspirin and colchicine (a drug used to manage gout attacks).

Diet should be the main source of vitamin B12 for most people. The elderly, vegans, vegetarians, and individuals with certain diseases that interfere with B12 absorption can benefit from B12 oral supplements. Vitamin B12 injections are approved by the FDA to treat certain conditions associated with B12 deficiency and are also used off-label to boost energy, improve brain health, and aid weight loss.

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