Vitamin B-12, also known as methylcobalamin, is an essential nutrient, but you only need a limited amount of it. The National Institutes of Health recommends 2.4 micrograms per day for adults, while pregnant and breast-feeding women need 2.6 to 2.8 micrograms. With vitamin B-12, a deficiency is more likely than a toxicity. Adverse effects from too much vitamin B-12 are rare because your body excretes excessive amounts through urine. If you take any kind of supplements and have abnormal symptoms, discuss your concerns with a doctor.
Vitamin B-12 helps in the manufacture of red blood cells and ensures proper functioning of your nervous system. When you don’t get the recommended daily amount, you might experience deficiency symptoms such as weakness, anemia and numbness. Meats, organ meats and shellfish are all natural sources of vitamin B-12. Certain foods, like breakfast cereals, are also fortified with the nutrient.
Vitamin B-12 from plants is not well-absorbed, so if you eat a vegetarian or vegan diet, you may need a supplement to avoid deficiency. The same is true if you have malabsorption issues from digestive disorders, or if you’re 50 or older. Because the liver stores vitamin B-12, most people have a reserve of the nutrient, not a deficiency. In addition, the liver also helps to get rid of any excess, so vitamin B-12 toxicity is rare.
Vitamins B-12 is found in most multivitamins, but is also available as a single supplement as a pill, sublingual tablet or nasal gel. Sometimes a doctor orders vitamins B-12 as an intramuscular injection, or a shot. Vitamin B-12 shots are dosed up to every two days for the first two weeks, then monthly thereafter, according to FamilyDoctor.org. There are no known overdose reactions from any of these forms of vitamin B-12, but you might experience skin redness or swelling at the site of injection.
While vitamin B-12 does not cause problems alone, there is the possibility of drug interactions. The most common side effect of such combinations is malabsorption of the vitamin B-12. Antibiotics, diabetes drugs and acid reflux medications are the most common culprits.