Vitamin B-12, or cobalamin, is a nutrient in animal-based foods, like meat, fish, eggs, poultry and dairy products. Vitamin B-12 does not appear in plant-based foods naturally, but many fortified foods and some types of nutritional yeast contain the vitamin. Examples of foods that contain cobalamin include liver, yogurt, haddock, cured ham, roasted chicken, Swiss cheese and salmon.
Water Solubility
You must consume vitamin B-12 daily, because it is a water-soluble vitamin. This means that the body excretes most excess vitamin B-12 in urine, although it can store the vitamin in the liver for years, according to National Institutes of Health online medical encyclopedia Medline Plus. Its water-solubility makes it unlikely that you will experience vitamin B-12 levels high enough for a long enough duration to cause harm unless you take an extremely high dose obtainable only through supplementation.
Dangers of High Levels
Although foods will not yield enough vitamin B-12 to cause harm, large loads taken either orally or intravenously can cause some complications. Specifically, diarrhea, rosacea, itching, rash and hives have been reported, according to the Mayo Clinic. It can also cause excess red blood cells or blood clots over extended periods. People who are susceptible to gout or hypokalemia, which is low potassium, may experience these conditions after excessive loads of B-complex vitamins over long periods, including vitamin B-12. Those with Leber's disease should not take vitamin B-12, because it can accelerate ocular atrophy.
Recommended Dosage
The recommended dose of vitamin B-12 varies by age. Infants should have 0.4 mcg per day until 6 months, then 0.5 mcg per day until 1 year. Children should have 0.9 mcg per day until 3 years, 1.2 mcg until 8 years and 1.8 mcg until 13 years. Children older than 13 and adults should have 2.4 mcg of vitamin B-12 per day.
Bottom Line
Vitamin B-12 is generally safe in normal doses and even those that exceed the daily recommended dose, because the body can pass excess in urine. There is no set upper limit for the vitamin for these reasons, but doses that exponentially exceed the daily recommendation can cause various health complications, including cardiovascular and liver damage. Unless recommended by your physician, maintain a dosage consistent with your daily requirements.
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