Vitamin B12 Shots for Weight Loss: Do They Work?

Key Takeaways:

• There’s not much research on B12 shots for weight loss.

• People with obesity tend to have lower vitamin B12 levels, but it’s unclear if B12 shots can promote weight loss.

• If you have a deficiency, B12 shots could improve fatigue, possibly helping you stay active to support weight loss.
  

Vitamin B12 is an essential vitamin, and low levels are linked to obesity. B12 shots could improve fatigue if you have a deficiency, but there’s not much research on them as a weight loss treatment.

Read on to learn more about B12 shots for weight loss, including how they could work and the benefits and risks.

You might have seen — or even taken — vitamin B12 as a tablet or gummy. But you can also get vitamin B12 shots, a prescription-only, injectable form of the supplement.

Vitamin B12 plays a role in energy production, nervous system and cognitive function, and red blood cell and DNA formation.

Vitamin B12, aka cobalamin, is a water-soluble vitamin and an essential nutrient found in foods like:

• Eggs

• Fish

• Meat

• Dairy

Plant-based foods don’t contain B12. If you eat a vegan, vegetarian, or plant-based diet, you can find the vitamin in fortified cereals and nutritional yeast.

There isn’t much research on whether vitamin B12 shots work for weight loss.

Research shows that vitamin B12 levels are lower in people with obesity than in those without obesity. Also, children and adolescents with obesity are more than four times as likely to have low B12 levels as those at a healthy body weight.

But we don’t know if low B12 causes obesity, whether obesity causes low B12, if both are associated with general health issues, or if it’s just a coincidence.

Research on Oral B12 Supplements and Weight Loss

When it comes to B12 supplementation, the research so far doesn’t look promising.

One study looked at adults age 65 and older who took oral folic acid and vitamin B12 or a placebo. After 2 years, the supplements didn’t make a significant difference in body mass index (BMI) or body fat mass.

In a 2022 study, participants with non-alcoholic fatty liver disease took an oral supplement of B12 or a placebo daily. After 12 weeks, there were no significant differences in weight or BMI.

Research suggests that B12 supplementation could improve metabolic syndrome, which includes:

• Abdominal obesity

• Insulin resistance

• High blood pressure (hypertension)

• High cholesterol

But further studies are needed to know if B12 could help with weight management.

B12 Shots Could Improve Fatigue

Vitamin B12 deficiency can lead to:

• Low energy

• Fatigue

• Shortness of breath

• Low tolerance for exercise

So, if you have a deficiency that’s treated through B12 shots, you might feel more energy. This energy boost could make it easier to cook nutritious meals, avoid mindless snacking, and move your body more, all of which can promote weight loss.

It’s unclear if B12 shots could help you lose weight if you don’t have a deficiency, though.

→ Learn more: Vitamin B12 for Weight Loss

You might need a B12 shot if you have a vitamin B12 deficiency.

You might have a vitamin B12 deficiency if you:

• Have obesity

• Don’t eat enough foods with B12

• Have been on medications like metformin or proton-pump inhibitors (PPIs) for a long time

• Have an autoimmune condition that prevents your body from absorbing B12 (pernicious anemia)

• Had surgery on your gastrointestinal tract

• Have a gastrointestinal disorder, like celiac disease or Crohn’s disease

• Are older

Symptoms of B12 deficiency include:

• Fatigue

• Heart palpitations

• Pale skin

• Numbness and tingling in the hands and feet

You can get a blood test to check your B12 levels and see if you’re deficient. If you are,  a healthcare provider can help you determine if oral B12 supplements or B12 shots are best to top up your levels.

Vitamin B12 is generally considered a safe supplement, even at high doses. Your body doesn’t store excess amounts of B12, so there isn’t a recommended upper limit.

That said, there are still some side effects to watch out for.

Side effects of vitamin B12 injections include:

• Diarrhea

• Feeling like your body is swollen

And less commonly:

• Headache

• Dizzines

• Itching

• Difficulty breathing

There’s also a risk of allergic reactions, including a severe, life-threatening reaction (anaphylaxis).

Check with your provider before taking a new dietary supplement to make sure it’s safe for you. You’ll need a prescription for B12 shots, so a healthcare professional can talk through any safety concerns.

There are weight loss treatments with more science behind them than B12 shots.

For example, people with obesity or overweight and a weight-related health condition might qualify for prescription weight loss medications. Options include glucagon-like peptide-1 (GLP-1) receptor agonist injections and oral weight loss drugs, such as:

• Semaglutide (Ozempic^®, Wegovy^®)

• Tirzepatide (Mounjaro^®, Zepbound^®)

• Liraglutide (Victoza^®, Saxenda^®)

• Metformin

• Topiramate 

There are also supplements that may support weight loss, like:

• Protein

• Fiber

• Magnesium

And lifestyle changes that promote healthy weight loss, including:

• Eating nutritious, whole foods

• Drinking plenty of water

• Doing more movement

• Getting enough sleep

• Lowering stress levels 

B12 supplementation may have a place in your weight loss treatment plan if you have a deficiency. But it’ll be one part of a holistic plan to help you reach your health and wellness goals.

→ Learn more: How to Lose Weight

There’s no evidence that B12 shots can directly aid weight loss, boost metabolism, or burn fat.

Here’s what to know if you’re considering them to help you on your weight loss journey:

• Low B12 is linked to obesity. You might have low B12 levels if you eat a vegetarian or vegan diet, have taken metformin for a long time, or have a gastrointestinal disorder.

• B12 shots could improve fatigue. Less fatigue = more energy to cook nutritious meals, stick to your eating plan, and move your body. B12 shots might not make a difference if you don’t have a deficiency, though.

• There are alternatives. Prescription medications, other supplements, and healthy lifestyle habits can help you reach your weight loss goals. B12 shots might be a part of your wider weight loss program.

Your best bet? Reach out to a healthcare provider to find out if you have low B12 levels and if B12 shots could improve your fatigue and overall health.

Get answers to frequently asked questions about B12 shots for weight loss.

Do B12 injections help you lose weight?

There isn’t any evidence that B12 injections can help you lose weight. If you have a vitamin B12 deficiency, B12 injections could improve symptoms like fatigue, and this increase in energy might help you eat healthier and do more physical activity to lose weight.

Will B12 shots give you more energy?

B12 shots might give you more energy if you have a vitamin B12 deficiency. One symptom of vitamin B12 deficiency is fatigue. If you don’t have a deficiency, B12 shots might not boost your energy levels.

Are B12 shots safe?

B12 shots are considered safe for most people, but there are exceptions. Check with your healthcare provider to make sure they’re safe for you, especially if you have a medical condition, are on medication, or are pregnant or breastfeeding. You’ll need a prescription for B12 shots, so a provider can talk through the pros and cons.

What are the benefits of B12 shots?

If you have low vitamin B12 levels, B12 shot benefits include reducing symptoms like fatigue, heart palpitations, and tingling and numbness in the hands and feet.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards.