Vitamin B12 is the name for a group of closely related vitamins. A deficiency can lead to serious problems such as anemia and permanent, severe nerve damage. While most people get enough vitamin B12 through their diet, some people have difficulty absorbing it into the bloodstream.
Vitamin B12 is available in tablet, sublingual tablet ("under the tongue" tablet), capsule, oral liquid, intramuscular injection, nasal spray, and patch form. Some forms are more reliable than others.
Vitamin B
12 is essential for healthy nerve and blood cells. It is also important for making DNA. In addition, the vitamin helps to break down homocysteine, an amino acid that can cause problems if it builds up to high levels. In particular, it is thought that high homocysteine may contribute to problems such as
cardiovascular disease or blood clots.
In food, vitamin B12 is bound to protein and is released by stomach acid. Then it binds to a substance known as intrinsic factor (which is produced in the stomach) and is absorbed into the bloodstream through the small intestine. Any problems in either of these steps can result in a deficiency.
To overcome such problems in absorption, vitamin B12 injections (or, more recently, nasal sprays) are often used. Although it was once thought that injections were the only way to treat deficiencies due to low or absent intrinsic factor, it is now known that oral forms can be just as effective, although much higher doses are required. Small amounts of vitamin B12 can be absorbed after oral consumption, even without any intrinsic factor.
Is Vitamin B12 Effective?
As you might expect, this vitamin is effective for treating vitamin B12 deficiencies. It may also be useful for treating hyperhomocysteinemia. There is not enough evidence to suggest that it works for most other uses.
Because it has been studied quite a bit, good information about vitamin B12 dosing is available. For some of the less studied uses, the most effective (and safe) doses have not yet been established. Recommended Dietary Allowances (RDAs) have been established for the vitamin.
Side Effects of Vitamin B12
Most people do not experience side effects, even with high doses. However, a few possible side effects have been reported in clinical studies. Some side effects of vitamin B12 may include:
- Diarrhea
- Rash
- Itching
- Blood clots in the legs.
(Click Vitamin B12 Toxicity to learn more, including potentially serious side effects you should report immediately to your healthcare provider.)
Most people can safely take vitamin B12, even at high doses. However, some people may be more likely to experience problems than others. Therefore, you should talk with your healthcare provider prior to taking the supplement if you have:
- Had a coronary stent
- Cobalamin or cobalt sensitivity
- Leber's disease
- Polycythemia vera
- Severe megaloblastic anemia
- Any allergies, including allergies to foods, dyes, or preservatives.
Also, let your healthcare provider know if you are:
Make sure to tell your healthcare provider about all other medicines you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.
(Click Vitamin B12 Safety for more information, including any available warnings and precautions.)
What If I Take an Overdose?
With some vitamins, taking too much can quickly cause serious problems. However, this is not the case with vitamin B12. Overconsumption of this vitamin is unlikely to cause problems for most people.
