Can B12 shots help with weight loss?

According to a 2019 study, vitamin B12 levels are lower in people with obesity than in those at a moderate weight. However, it did not prove that the vitamin can help a person lose weight. While b12 injections for weight loss,are necessary for some people who cannot absorb the vitamin in other ways, they have some risks and side effects. Some risks, such as fluid buildup in the lungs or a blood clot, can be severe. Learn about what B12 shots are, how they work, risks and side effects, and more.

What is Vitamin B12?

Vitamin B12 is required for creating new red blood cells. It is necessary for the healthy functioning of nerves and the brain. Vitamin B12 is cobalamin, an enzyme co-factor that is necessary for the synthesis of DNA. B12 is also involved in the synthesis of hormones and neurotransmitters.

B12 is mainly found in meat, poultry, fish and shellfish, eggs, and dairy. Non-animal sources include fortified or enriched milk substitutes, grains, and nutritional yeast. So, is weight loss with shots of B12 plausible?

B12 and Weight Loss: How a B12 Shot Can Support Weight Loss

Vitamin B, in general, increases energy. Two B vitamins are credited with providing the most significant energy benefits. They are vitamin B6 and vitamin B12. Vitamin B6 is also known as pyridoxine. It helps regulate glycogen, which impacts energy levels. It also affects appetite. Vitamin B12 is also known as cobalamin. It plays a role in cell metabolism. This has implications whether you feel energy or fatigue.

Increased energy is one of the most promising benefits of B12. This enhanced energy makes it easier to get to the gym. You can also work out harder because you don’t feel fatigued. But do B12 injections promote weight loss

What are they?

B12 is a water-soluble vitamin present in some foods. It is available as an oral dietary supplement in tablet form, or doctors can also prescribe it as a shot. B12 supplements may be necessary for some people as the body cannot make it.

B12 is essential for the following:

  • development and functioning of the central nervous system
  • formation of red blood cells
  • synthesis of DNA, the genetic material in the cells
  • functioning of two enzymes responsible for an array of chemical reactions

Compounds containing B12 are also called cobalamin. Two common forms include cyanocobalamin and hydroxocobalamin.

Doctors typically use B12 shots to treat vitamin B12 deficiency. One cause of B12 deficiency includes pernicious anemia, which reduces red blood cells when the intestines cannot absorb enough vitamin B12. 

A healthcare professional delivers the shot into a muscle, bypassing the intestinal tract. This way, the body can receive what it needs.

How they work

Research from 2019 notes an inverse relationship between obesity and low vitamin B12 levels. This means that people with obesity tend to have lower levels than those with a moderate weight.

However, the research authors emphasize that this does not indicate the shots can help a person lose weight, as no proof exists of a causal relationship. They could not determine whether obesity lowers B12 levels or if low B12 levels predispose someone to obesity.

In explaining such research findings, Pernicious Anemia Relief (PAR) notes that obesity may stem from the habits of individuals who have a B12 deficiency or their co-occurring conditions. Conversely, B12 deficiency may affect metabolism, which plays a role in obesity. PAR recommends that the only people who should take B12 shots are those with B12 deficiency who cannot absorb the vitamin when they take it orally.

Risks and side effects

In rare situations, B12 shots can cause allergic reactions, including:

  • itching
  • rash
  • anaphylaxis is a life-threatening condition that can cause a fast heartbeat and difficulty breathing

Other side effects that can occur include:

  • shortness of breath, fast weight gain, and swelling
  • congestive heart failure is the inability of the heart to pump blood adequately
  • pulmonary edema is the buildup of fluid in the lungs
  • peripheral vascular thrombosis is the obstruction of a vein with a blood clot
  • hypokalemia, low potassium levels that can cause irregular heartbeats and muscle weakness
  • fever
  • tingling, numbness, and joint pain
  • swollen tongue
  • polycythemia is an increase in the red blood cell mass

Do people need B12 shots?

B12 shots are not necessary for weight loss. For most people, a balanced diet provides the nutrients needed for wellness, including vitamin B12. Some food sources of the vitamin include:

  • milk and milk products
  • fish
  • red meat
  • eggs
  • poultry

However, a person with B12 deficiency may not be able to absorb enough of the vitamin from their diet. When this occurs, they may need supplements or B12 shots.

When to contact a doctor

People with obesity or those who are concerned about their weight can contact a doctor. They can provide recommendations on achieving a moderate weight in a healthy, sustainable manner. Additionally, individuals interested in B12 should consult their doctor before taking an oral supplement. If they think they may have a B12 deficiency, a blood test can determine this.


In conclusion, while Vitamin B12 injections have been touted as a potential aid for weight loss due to their role in metabolism regulation, scientific evidence supporting their direct effectiveness in causing weight reduction is limited. While a deficiency in Vitamin B12 can impact energy levels and metabolism, leading to weight gain in some cases, its supplementation through injections might not directly induce weight loss in individuals with adequate B12 levels.

 Moreover, relying solely on B12 injections for weight management might overlook other crucial factors like diet, exercise, and overall lifestyle changes necessary for sustainable and healthy weight loss. As such, while B12 injections may benefit those with a deficiency, their use solely for weight loss should be cautiously approached and consulted with a healthcare professional.