Vitamin B12 Shots: A Guide

Medically Reviewed By Kim Rose-Francis RDN, CDCES, CNSC, LD

Vitamin B12 shots are injections used to treat deficiencies in vitamin B12. Deficiencies may occur due to dietary habits, gastrointestinal issues, and other conditions. Research is ongoing into the effectiveness of injections for people without deficiencies. Vitamin B12, or cyanocobalamin, is an essential nutrient that contributes to many functions, such as:

If you have a vitamin B12 deficiency, your doctor may recommend increasing vitamin B12 in your diet. They may also recommend supplements or injections.

This article explains the benefits, uses, and risks of vitamin B12 injections, as well as recommended intake levels.

How do vitamin B12 shots work?

Vitamin B12 ampoules
Yevhenii Khil/Getty Images

Vitamin B12 injections contain a synthetic form of vitamin B12, usually given via a muscle.

Sometimes, injecting it into a muscle can help increase the supplement’s effectiveness. Injecting into a vein may mean some of the vitamin is wasted, as it can leave the body via the urine.

Other ways of supplementing with vitamin B12 include:

  • oral tablets or capsules
  • oral or nasal sprays
  • drops for under the tongue

Your doctor can provide advice on the most appropriate option for you.

What are vitamin B12 shots for?

Doctors may recommend vitamin B12 injections to treat vitamin B12 deficiencies. Vitamin B12 deficiency is rare Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source , but treatment is important for people who do have low levels.

Symptoms of B12 deficiency include:

Contact your doctor to discuss injections or supplements if you experience any conditions or risk factors related to vitamin B12 deficiency.

The following factors may increase the likelihood of having a B12 deficiency.

Read more about who vitamin B12 supplements may help.

Dietary patterns

Many people can meet their vitamin B12 requirements through diet. However, vitamin B12 is mostly Trusted Source National Institutes of Health Office of Dietary Supplements Governmental authority Go to source present in animal products. As a result, people who include little to none of these in their diet may be more likely to have a deficiency.

A 2014 literature review Trusted Source International Journal of Obesity Peer reviewed journal Go to source suggests that 0–86.5% of people following vegetarian and vegan diets had a vitamin B12 deficiency. This depended on factors such as age and pregnancy. The review also indicated that vegans who did not take vitamin B12 supplements were most likely to have a deficiency.

Due to these results, the reviewers suggested that vegetarians and vegans consider using vitamin B12 supplements.

Read more about food sources of vitamin B12.

Gastrointestinal conditions

Some gastrointestinal conditions may affect how vitamin B12 is digested or absorbed, such as:

Vitamin B12 injections may be more helpful for people with gastrointestinal conditions than oral products. This is because they don’t need to be digested, which avoids the risk of low absorption.

Older adults

A 2015 review suggests that adults over the age of 60 may be more likely to have a vitamin B12 deficiency. This may be because the ability to absorb vitamin B12 effectively can decrease Trusted Source Department of Health and Human Services Governmental authority Go to source with age or when using certain medications.

Other factors

Risk factors for having a vitamin B12 deficiency may include:

  • high alcohol intake
  • AIDS
  • some inherited conditions

How much vitamin B12 do I need?

Clinicians estimate vitamin B12 requirements using values such as:

  • Recommended dietary allowance (RDA): RDA refers Trusted Source National Institutes of Health Office of Dietary Supplements Governmental authority Go to source to a daily intake that, on average, is enough to meet the nutritional requirements of almost all people without underlying health conditions.
  • Adequate intake (AI): AI is the average intake level taken by people who are considered Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source to be healthy in studies.

The NIH Trusted Source National Institutes of Health Office of Dietary Supplements Governmental authority Go to source estimates the following RDA or AI values for vitamin B12:

Age or conditionAmount
0–6 months0.4 micrograms (mcg)
7–12 months0.5 mcg
1–3 years0.9 mcg
4–8 years1.2 mcg
9–13 years1.8 mcg
14 years or older2.4 mcg
If you are pregnant, at any age2.6 mcg
If you are lactating, at any age2.8 mcg

However, these amounts are general estimations. Appropriate amounts can vary per person based on many other factors. These can include whether you have an underlying health condition.

The United States Food and Nutrition Board hasn’t set Trusted Source National Institutes of Health Office of Dietary Supplements Governmental authority Go to source any upper limit on vitamin B12 intake. The risks of toxicity are usually low.

Some injection courses may provide up to 7 daily doses of 100 mcg, or up to 1000 mcg at once.

When should you avoid vitamin B12 shots?

Vitamin B12 injections may not be suitable for people who have a history of:

  • allergic reaction or sensitivity to cobalt or vitamin B12
  • Leber disease
  • kidney disease or impaired kidney function

Also, vitamin B12 injections may not be necessary for people without a deficiency.

Most Trusted Source National Institutes of Health Office of Dietary Supplements Governmental authority Go to source people can get enough vitamin B12 from dietary sources. The 2020–2025 Dietary Guidelines for Americans Trusted Source Dietary Guidelines for Americans (USDA) Governmental authority Go to source recommends trying to meet your nutritional needs through a balanced diet before relying on supplements. A doctor or registered dietitian can provide tailored nutritional advice.

Unprescribed ‘wellness’ or weight loss treatments

Some wellness companies and alternative medicine providers offer vitamin injections without a prescription or proper medical evaluation. Some companies have also illegally mislabeled or missold Trusted Source Food and Drug Administration (FDA) Governmental authority Go to source vitamin products as health cures or weight loss treatments.

However, these uses and supplements are not regulated by the Food and Drug Administration (FDA). This means their safety and effectiveness cannot be confirmed.

Some studies suggest that people with obesity may be more likely to have a vitamin B12 deficiency. However, further research is necessary to confirm any link. There is also very little evidence to suggest that vitamin B12 injections are helpful for weight loss.

If you believe you may benefit from vitamin B12 injections, talk with your doctor. They can assess your health and provide safe and effective treatment recommendations.

Are there any risks to vitamin B12 shots?

As the NIH Trusted Source National Institutes of Health Office of Dietary Supplements Governmental authority Go to source suggests, the risks of toxicity from too much vitamin B12 are low. Even large doses may be considered safe, as the body does not store vitamin B12 in large amounts.

However, while risks of severe toxicity are low, some side effects are still possible, such as:

  • temporary symptoms, such as itching, swelling, or diarrhea
  • allergic reaction
  • damage from the injection
  • hypokalemia, or low potassium levels
  • infection
  • negative interactions with certain medications, such as:
    • metformin (Fortamet, Glucophage, Riomet)
    • medications to reduce gastric acid, such as proton pump inhibitors or H2 receptor antagonists

Always talk with a doctor before using vitamin B12 supplements. Make sure to inform them of any prescription or over-the-counter medications, supplements, or herbal remedies you take.

Contact your doctor as soon as possible if you experience any new or changing symptoms after using vitamin B12 injections or supplements.

Learn more about allergic reaction symptoms and when to see a doctor.

Summary

Vitamin B12 injections can be an effective way of treating a deficiency. Vitamin B12 deficiencies can be caused by many factors, such as older age, gastrointestinal conditions, and vegan or vegetarian diets.

Supplementing with vitamin B12 is generally considered safe, as there is a low risk of toxicity. However, side effects such as temporary swelling, allergic reaction, and interactions with other medications are possible.

Also, injections are not typically recommended for people without a vitamin B12 deficiency.

Talk with your doctor for advice if you believe you may benefit from vitamin B12 supplements or injections.

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Medical Reviewer: Kim Rose-Francis RDN, CDCES, CNSC, LD
Last Review Date: 2023 Sep 18
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