Vitamin B12 is a water-soluble vitamin that is part of the vitamin B complex.

Vitamin B12, like the other B vitamins, is important for metabolism. It helps in the formation of red blood cells and in the maintenance of the central nervous system.

Vitamin B12 is found in eggs, meat, poultry, shellfish, and milk and milk products.

The human body stores several years' worth of vitamin B12, so nutritional deficiency of this vitamin is extremely rare.

However, deficiency can result from being unable to use vitamin B12.

Strict vegetarians or vegans who are not taking in proper amounts of B12 by way of supplements are also prone to a deficiency.

Low levels of B12 can cause anemia as well as numbness or tingling in the extremities and other neurologic symptoms such as weakness and loss of balance.

Recommended dietary allowances (RDAs) are defined as the levels of intake of essential nutrients that, on the basis of scientific knowledge, the Food and Nutrition Board judges to be adequate to meet the known nutrient needs of practically all healthy persons.

Because vitamin B12 comes primarily from animal products, people who follow a strict vegetarian diet and do not consume eggs or dairy products may require vitamin B12 supplements. (Non-animal sources of vitamin B12 exist but are highly variable in their B12 content, and are therefore unreliable sources.)

Many people think that if some vitamins are good, a lot is better.
This is not always the case, and high doses of certain vitamins are actually toxic.
Read about the specific vitamins and check with your health care provider if you are unsure about how much to take -- and how much may be too much.

The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods and take a "Standardized" (quality) multivitamin supplement.