Vitamin B-12 is an essential water-soluble vitamin needed to help your body make red blood cells and DNA. It is also needed for normal neurological function. Certain groups of people are at risk of vitamin B-12 deficiencies due to an inability to properly absorb the vitamin and may require high doses, up to 1,000 mcg, of vitamin B-12 to meet their needs. Taking high doses of vitamin B-12 has not been shown to cause any adverse effects, but consult with your doctor before taking high doses.
Recommended Needs
Your daily vitamin B-12 recommendations are based on guidelines provided by the Food and Nutrition Board at the Institute of Medicine. They are based on the average daily need to meet nutrient levels in healthy people. The recommendations vary based on age. Infants 0 to 6 months require 0.4 mcg, and ages 7 months to 12 months require 0.5 mcg. Children age 1 to 3 years need 0.9 mcg of vitamin B-12 a day to meet requirements, 4 to 8 years need 1.2 mcg and 9 to 13 need 1.8 mcg. Everyone else over the age of 14 needs 2.4 mcg of vitamin B-12 a day.
Deficiencies
Inadequate intakes of vitamin B-12 can cause megaloblastic anemia, loss of appetite, weight loss, tingling and numbness in hands and feet, loss of memory, confusion, depression and dementia. Groups at risk of deficiency include older adults, people with pernicious anemia, people with malabsorption and those with a poor dietary intake. Vitamin B-12 is bound to protein in foods and requires the acidity of the stomach to free itself from absorption. Older adults have less acid in their stomachs and may not absorb enough vitamin B-12 from the food they eat. In addition, in the stomach, vitamin B-12 combines with intrinsic factor, which is necessary for absorption. Individuals with pernicious anemia lack intrinsic factor and cannot absorb vitamin B-12.
Treating B-12 Deficiency
Vitamin B-12 deficiency is typically treated with an injection because most cases of deficiency are related to malabsorption. However, high doses of oral vitamin B-12, up to 2,000 mcg, have been effective in treating some cases of deficiency, according to the National Institutes of Health Office of Dietary Supplements. Your doctor should determine the amount of vitamin B-12 you need and the best method of delivery.
Toxicity
High doses of vitamin B-12 do not cause toxicity or adverse effects, according to the Linus Pauling Institute. In fact, the Food and Nutrition Board of the Institute of Medicine has not established a tolerable upper limit for vitamin B-12. As a water-soluble vitamin, any amount taken in excess is excreted in the urine. According to Drugs.com, 50 to 98 percent of the vitamin B-12 given as an injection is excreted in the urine.
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