Most B vitamins are excreted in the urine relatively quickly. However, vitamin B12 can be stored by the liver and kidney. This vitamin exists in the chemical forms known as cyanocobalamin or hydroxocobalamin. Vitamin B12 can be administered by injection into the muscle to treat deficiency caused by pernicious anemia, which is a consequence of vitamin malabsorption.
Functions of B Vitamins
Vitamin B12 is a necessary part of synthesizing DNA, creating new red blood cells and general maintenance of the nervous system. The National Institutes of Health, or NIH, says it also is a key agent in helping to make enzymes for metabolizing DNA, RNA and proteins. Due to the varied functions of vitamin B12, an imbalance can result in a number of health issues. It is therefore crucial to maintain the recommended levels of vitamin B12 in order to support good health.
Safety
The NIH says injectable vitamin B12 is usually safe at the common dose of about 1 mg per month with very few side effects. Higher doses of vitamin B12 can cause certain side effects, mostly involving the peripheral and central nervous systems. Effects can be felt as tingling or numbness in the face or arm, palpitations and anxiety. Severe side effects can manifest as anemia related to high folic acid levels and visual or thyroid problems.
Effects of Vitamin B9
Folic acid, commonly called vitamin B9, can obscure the harmful effects of vitamin B12 insufficiency, says the NIH. Therefore, injections of vitamin B12 must take this complex interaction into account. Insufficiency of vitamin B12 can lead to anemia and neurological damage. High levels of folic acid, however, can mask anemia by reversing it. Yet folic acid will not correct neurological damage caused by vitamin B12 deficiency. Folic acid may also cause a patient's anemia to get worse, and can lead to severe cognitive dysfunction caused by insufficient vitamin B12 levels. As a result, permanent nerve injury may occur if vitamin B12 deficiency is not treated properly. This masking problem is why folic acid from supplements or foods should not be more than 1 mg per day in adults.
Interactions With Medicines
Certain medicines can interact with vitamin B12, says the NIH. Some medicines can adversely affect vitamin B12 levels in the blood. Vitamin B12 administered with the antibiotic chloramphenicol can interfere with red blood cell function. Drugs known as proton pump inhibitors used for gastroesophageal reflux disease and peptic ulcers can interfere with absorption of vitamin B12. Histamine receptor agonist medicines used to treat peptic ulcers also may interfere with vitamin B12 absorption. Metformin, a hypoglycemic medicine used to treat diabetes, can reduce vitamin B12 absorption by causing bacterial overgrowth or changing intestinal motility.
B-Vitamins from Supplements
Taking oral supplements is a good way to maintain the proper levels of B vitamins. The U.S. Department of Agriculture lists the recommended dietary allowance, or RDA, of the B vitamins. Pregnant women should have 600 mcg of vitamin B9. Adults 19 to 50 years old should have 1.3 mg of vitamin B6, while adults older than 50 should have 1.5 to 1.7 mg. All adults should have 2.4 mcg of vitamin B12, 1 to 1.2 mg of vitamin B1, 1.1 to 1.3 mg of vitamin B2 and 5 to 10 mg of vitamin B5.
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