What Is the Normal Intramuscular Dose of Vitamin B12?

A growing number of people are turning to vitamin B12 shots for weight loss. Unfortunately, there's no evidence that these shots burn fat or boost your metabolism. They do, however, help prevent and treat vitamin B12 deficiency — a major risk factor for anemia, depression, fatigue and memory problems. Your body needs this nutrient to produce DNA and red blood cells, among other biological functions.

A man administers and injection into his own arm. (Image: RobertoDavid/iStock/Getty Images)

Tip

The normal intramuscular dose of vitamin B12 is 30 to 100 micrograms daily for up to 10 days followed by maintenance doses. This is often enough to prevent and reverse a deficiency. In some cases, higher doses are needed.

Why Is Vitamin B12 Important?

Cobalamin, or vitamin B12, plays a key role in DNA synthesis and hemoglobin production. It also supports the proper functioning of the nervous system and regulates homocysteine metabolism. According to the Linus Pauling Institute, elevated homocysteine levels may affect cardiovascular health and increase heart disease risk.

This water-soluble vitamin is found in animal foods, such as clams, mussels, salmon, beef and eggs, as well as in nutritional yeast and fortified foods. Your body cannot produce it on its own. Therefore, it's no surprise that 1.5 percent to 15 percent of the population is deficient in vitamin B12, according to the National Institutes of Health (NIH).

As the NIH points out, vitamin B12 deficiency tends to be more common in strict vegetarians, vegans and people with inflammatory bowel disorders, atrophic gastritis or pernicious anemia. Dietary supplements are poorly absorbed and may not always help.

Vitamin B12 has a direct impact on your mood and mental health. According to June 2012 case report published in the journal Child and Adolescent Psychiatry and Mental Health, low levels of this nutrient may cause psychiatric symptoms, such as poor mental focus, irritability, impaired attention and insomnia. In the long run, vitamin B12 deficiency may contribute to depression, psychosis, dementia and other mental illnesses.

A clinical trial conducted on 199 patients and published in the Open Neurology Journal in November 2013 indicates that taking vitamin B12 and antidepressants may improve depressive symptoms. Another study, which appeared in the American Journal of Clinical Nutrition in April 2016, found a strong link between vitamin B12 deficiency and poor memory performance. Low levels of this nutrient may also contribute to cognitive decline and accelerate brain atrophy.

Role of Vitamin B12 Shots

Injectable solutions and dietary supplements contain cyanocobalamin, the primary form of vitamin B12. Hydroxocobalamin and methyl B12 injections are available, too. In a small clinical trial conducted on 50 children with autism and published in Journal of Child and Adolescent Psychopharmacology in November 2016, subjects who received methyl B12 every three days for eight weeks experienced significant improvements in their symptoms.

Vitamin B12 shots are prescribed for pernicious anemia and other disorders that affect the body's ability to absorb and synthesize cobalamin. Treatment aims to raise vitamin B12 levels in the bloodstream and prevent or reverse a deficiency. As the NIH points out, injectable vitamin B12 has a higher absorption rate than oral formulas. However, high doses of this nutrient in oral form may be just as effective.

Nowadays, vitamin B12 injections are marketed as a cure-all. Proponents say that they boost your energy and stamina, improve athletic performance and accelerate fat loss. However, these claims lack scientific evidence. According to the Mayo Clinic, vitamin B12 shots won't increase your energy unless you're deficient in this nutrient. Furthermore, they have no effect on metabolism and body weight.

Warning

Vitamin B12 shots are unlikely to boost your energy or help you get leaner. This form of treatment isn't a cure-all.

B12 Injection Dosage

B12 shot dosage depends largely on the condition that is being treated. Gastrectomy, bariatric surgery and other stomach operations, for example, can reduce vitamin B12 absorption.

According to a January 2017 review in Obesity Surgery, 350 micrograms of oral vitamin B12 is often enough to prevent deficiencies in gastric surgery patients. The typical dose for intramuscular injections, though, is around 1,000 micrograms per month.

If you're deficient in vitamin B12, your doctor may prescribe 30 to 100 micrograms of cyanocobalamin daily for five to 10 days. Maintenance doses of 100 to 200 micrograms per month may be required, as well.

Pernicious anemia develops because the body is unable to make enough healthy red blood cells due to a lack of vitamin B12. People with this condition can't absorb vitamin B12 from food because they don't have the necessary protein, intrinsic factor, found in the stomach that aids in absorption of the B vitamin.

Pernicious anemia is usually treated with 100 micrograms of cyanocobalamin daily for at least six days, followed by 100 micrograms monthly for life. Itching, mild diarrhea, congestive heart failure and fluid buildup in the lungs are all potential side effects. Individuals who are sensitive to cyanocobalamin may experience anaphylactic shock, a severe allergic reaction.

A review published in the journal Frontiers in Medicine in August 2016 states that pernicious anemia patients often require lifelong vitamin B12 shots. This treatment isn't just expensive, but also potentially dangerous because of its side effects. In clinical trials, daily oral doses of 1,000 micrograms of vitamin B12 have been shown to be just as effective as the injectable form.

If you're anemic or deficient in this nutrient, ask your doctor about the best ways to raise your vitamin B12 levels. Injections are not the only option.

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