Vitamin B12 for Weight Loss: Does It Work?

Craig Primack, MD, FACP, FAAP, FOMA

Reviewed by Craig Primack, MD, FACP, FAAP, FOMA

Written by Rachel Sacks

Published 04/06/2024

Since the dawn of the Internet (and probably well before), there have been several solutions sold for weight management — including vitamins for weight loss. One in particular, vitamin B12 supplements, are often touted as a solution for weight management.

There are mixed claims when it comes to vitamin B12 shots or pills. Some say this supplement gives you energy and boosts your metabolism while other research has shown mixed results when it comes to weight loss.

But what’s fact and what’s fiction when it comes to this buzzy supplement? Weight loss is already a tricky subject so we’re getting to the bottom of vitamin B12 for weight loss and answering questions like:

  • What does B12 do for you?

  • Does B12 help you lose weight?

  • What is the best way to take B12?

And more specifically, what does vitamin B12 do for you?

Vitamin B12, also known as cobalamin, isn’t just a popular supplement marketed to help people lose weight— it’s an essential water-soluble vitamin necessary for brain function, heart health, energy levels and more as well as forming DNA and red blood cells.

As the name implies, water-soluble vitamins dissolve in water. So while there’s no best time to take B12, you don’t need to take it with food for it to be fully absorbed.

Many foods naturally contain B12, such as:

  • Fish

  • Meat

  • Poultry

  • Eggs

  • Dairy products

Plant-based foods don’t provide B12 but fortified breakfast cereals or nutritional yeast are good sources for vegetarians and vegans.

B12 is available as either oral tablets or prescription vitamin B12 injections, sometimes referred to as B12 shots.

Benefits of B12

Is vitamin B12 good for you? Absolutely, as B12 has been shown to support brain function and additional research suggests vitamin B12 supplements (along with other B vitamins) may help improve mood disorders.

One benefit of B12 that’s been particularly noteworthy is its effects on metabolism (the chemical reactions in the body's cells that change food into energy).

Although research is still limited, some studies suggest that vitamin B12 could affect metabolic syndrome, a health issue that includes metabolic abnormalities like insulin resistance, high blood pressure and obesity.

But does vitamin B12 give you energy? While more studies are needed to see how vitamin B12 affects metabolism in humans, there has been research on the effects of a vitamin B12 deficiency.

Vitamin B12 Deficiency

One example of vitamin B12 deficiencies is older adults struggling with cognitive issues and memory function.

But since you’re curious about B12 and weight loss, you probably want to know: does vitamin B12 make you gain weight?

Not quite. Rather, the question should be “Does B12 deficiency cause weight gain” as some evidence suggests low levels of B12 may be linked to weight gain and obesity.

A study of 976 people found that low levels of vitamin B12 were connected to a higher risk of overweight or obesity.

Another study of over 600 young adults and children looked at the link between vitamin B12 levels and body mass index (BMI), with lower B12 levels resulting in higher body weight.

And what about metabolism, a buzzy word associated with weight loss that’s how your body gets energy from food? Does B12 increase metabolism?

Technically, B12 doesn’t increase metabolism per se. But B12 could affect your metabolism, as one study suggests that a deficiency could be linked to increased fat accumulation and obesity.

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But while these studies are promising, they’re not conclusive enough to say that vitamin B12 for weight loss works.

While lower levels of vitamin B12 are associated with higher BMI and body fat, taking vitamin B12 supplements didn’t change body composition over the long term.

More research is needed on the effects B12 has on body weight and BMI. But along with healthy lifestyle choices and weight loss medication prescribed by a doctor, B12 could play a supporting role in weight loss goals.

Vitamin B12 and Weight Loss Drugs

So does B12 help with weight loss? On it’s own, no.

Vitamin B12 for weight loss isn’t the be-all, end-all solution. The reality is that, along with other weight management tools, like medications and lifestyle changes, certain vitamins for weight loss like B12 can support a healthy weight.

Other vitamins like vitamin D and magnesium may also support weight loss, and can often be consumed via food — much like B12. Just another reason why a balanced diet is important, to ensure you’re getting all the vitamins that can help you reach your weight loss goals.

Eating more foods that contain B12 is one way to help boost a deficiency.

But if you’re vegan or vegetarian or have a medical condition like pernicious anemia (when your body doesn’t have enough B12 to produce the amount of red blood cells it needs), vitamin B12 injections may be recommended.

Vitamin B12 injections are generally safe, with few side effects and the possibility of allergic reactions.

Depending on your health and weight journey, your healthcare provider may prescribe vitamin B12 shots for weight loss alongside other medications like metformin, a diabetes medication used off-label for weight loss.

Taken as weight loss shots, there are plenty of benefits of metformin from weight management to improved cognitive function and more.

The effectiveness of taking Vitamin B12 for weight loss remains a topic of debate. There are certainly benefits of vitamin B12, whether you take it as a pill or B12 shots, along with risks.

  • B12 is a crucial vitamin necessary for wellness, supporting energy production (aka metabolism), brain function, heart health and more.

  • Does B12 help you lose weight? Research is mixed as some studies suggest deficiency leads to weight gain, while others suggest it could help weight loss efforts.

  • B12 may be combined with other medications as part of a weight loss program, such as metformin.

If you’re looking for more information on weight management or a weight loss program that’s best for you, you can seek medical advice from a healthcare provider.

9 Sources

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  3. Ashok, T., Puttam, H., Tarnate, V. C. A., Jhaveri, S., Avanthika, C., Trejo Treviño, A. G., Sl, S., & Ahmed, N. T. (2021). Role of Vitamin B12 and Folate in Metabolic Syndrome. Cureus, 13(10), e18521. Retrieved from
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  5. Baltaci, D., Kutlucan, A., Turker, Y., Yilmaz, A., Karacam, S., Deler, H., Ucgun, T., & Kara, I. H. (2013). Association of vitamin B12 with obesity, overweight, insulin resistance and metabolic syndrome, and body fat composition; primary care-based study. Medicinski glasnik : official publication of the Medical Association of Zenica-Doboj Canton, Bosnia and Herzegovina, 10(2), 203–210. Retrieved from
  6. Aureli, A., Recupero, R., Mariani, M., Manco, M., Carlomagno, F., Bocchini, S., Nicodemo, M., Marchili, M. R., Cianfarani, S., Cappa, M., & Fintini, D. (2023). Low Levels of Serum Total Vitamin B12 Are Associated with Worse Metabolic Phenotype in a Large Population of Children, Adolescents and Young Adults, from Underweight to Severe Obesity. International journal of molecular sciences, 24(23), 16588. Retrieved from
  7. Boachie, J., Adaikalakoteswari, A., Samavat, J., & Saravanan, P. (2020). Low Vitamin B12 and Lipid Metabolism: Evidence from Pre-Clinical and Clinical Studies. Nutrients, 12(7), 1925. Retrieved from
  8. Oliai Araghi, S., Braun, K. V. E., van der Velde, N., van Dijk, S. C., van Schoor, N. M., Zillikens, M. C., de Groot, L. C. P. G. M., Uitterlinden, A. G., Stricker, B. H., Voortman, T., & Kiefte-de Jong, J. C. (2020). B-vitamins and body composition: integrating observational and experimental evidence from the B-PROOF study. European journal of nutrition, 59(3), 1253–1262. Retrieved from
  9. Cyanocobalamin Injection. (n.d.). MedlinePlus. Retrieved from
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