Print this page

Vitamin B12 – Vitamin Facts

What is vitamin B12?

Vitamin B12, also known as cyanocobalamin, is a water-soluble vitamin that is part of the B vitamin family. These vitamins help support adrenal function, help calm and maintain a healthy nervous system, and are necessary for key metabolic processes. Taking vitamin B12 is important to DNA synthesis and maintaining healthy nerve cells.

Why is vitamin B12 necessary?

Knowing the facts about the B12 vitamin and its benefits is vital: this essential micronutrient affects the development and maintenance of red blood cells, nerve cells, and normal myelination (covering) of nerve cells. It also aids in the production of DNA and RNA, and the production of neurotransmitters.

What are the signs of a Vitamin B12 deficiency?

Symptoms of vitamin B12 deficiency include fatigue, muscle weakness, shortness of breath, dizziness, numbness, heart palpitations, bleeding gums and mouth sores, nausea, poor appetite and diarrhea. Vitamin B12 deficiency symptoms may present themselves slowly and may not be recognized for some time. A deficiency of B12 can produce pernicious anemia, which can lead to memory loss, confusion and even dementia.

Since we obtain vitamin B12 only from animal foods in our diet, vitamin B12 deficiencies tend to develop among strict vegetarians, especially vegan children, who eat no animal products. However, the elderly, and those who are unable to absorb vitamin B12 from the intestinal tract are also at risk, as well as those who are pregnant or who suffer hemorrhage or intestinal disorders.

How much, and what kind, does an adult need?

According to the National Institutes of Health (NIH), the average daily U.S. Recommended Dietary Allowance (RDA) is:

  • people age 14 and older, 2.4 mcg;
  • for adult and adolescent pregnant females, 2.6 mcg
  • and for adult and adolescent lactating females, 2.8mcg.

People over 50 years of age should consume vitamin B12-fortified foods, or take a vitamin B12 supplement – 25-100 mcg per day has been used to maintain vitamin B12 levels in older people.

Dr. Weil recommends taking 50 mcg as part of a B-Complex that contains a full spectrum of B vitamins, including biotin, thiamin, the B12 vitamin, riboflavin and niacin.

How much does a child need?

The NIH recommendations:

  • infants 0-6 months, 0.4 mcg
  • infants 7-12 months, 0.5 mcg
  • toddlers 1-3 years, 0.9 mcg
  • children 4-8 years, 1.2mcg
  • children 9-13 years, 1.8 mcg.

How do you get enough vitamin B12 from foods?

Animal-derived foods are the best food sources of vitamin B12, including dairy products, eggs, meat, fish, poultry, and shellfish.

Are there any risks associated with too much vitamin B12?

Vitamin B12 is considered safe and non-toxic, but other B-vitamins can cause problems in large doses.

Are there any other special considerations?

Taking sublingual tablet or oral spray form of vitamin B12, both of which are absorbed by the blood vessels in the mouth, is often better for seniors who may have trouble absorbing the vitamin from the stomach.

Vitamin B12 absorption and/or depletion may occur in those who use alcohol excessively, who take antibiotics, use stomach-acid controlling drugs, including H-2 blockers and proton pump inhibitors, or who take Metformin to treat type 2 diabetes. Nicotine can also lower serum levels of B12.

In addition, potassium supplements can reduce absorption of vitamin B12, and there is some evidence that vitamin C in supplements can interfere with obtaining the vitamin B12 found in foods.

Updated by: Andrew Weil, M.D., and Brian Becker, M.D., on Oct. 29th, 2012


Do you know what supplements are right for you?
Everyone’s dietary needs are different based on a number of factors including lifestyle, diet, medications and more. To get your supplement recommendation, take the Weil Vitamin Advisor. This 3-step questionnaire requires just minutes to complete, and generates a free, no-obligation vitamin and nutritional supplement recommendation that is personalized to meet your unique nutritional needs.