Vitamin B-12

Vitamin B-12 is a vitamin the body uses to make and support healthy nerve cells. It's also used to make healthy red blood cells and the genetic material inside cells called DNA. Vitamin B-12 also is called cobalamin.

Food sources of vitamin B-12 include poultry, meat, fish and dairy products. Food companies also may add vitamin B-12 to breakfast cereals. Some people may take it as a vitamin by mouth. Healthcare professionals might prescribe vitamin B-12 injectio ns or nasal spray to treat people with very low vitamin B-12 levels.

Having seriously low vitamin B-12 levels, called vitamin B-12 deficiency, isn’t common in the U.S. People who follow a vegetarian or vegan diet can sometimes have low levels. This is because plant foods don't have vitamin B-12.

Older adults and people who have had stomach surgery also are at risk because they may not absorb the vitamin as well. People with digestive conditions such as celiac disease and Crohn's disease also are at risk of low vitamin B-12 levels.

People with very low vitamin B-12 levels can have symptoms such as fatigue, muscle weakness, stomach problems, nerve damage, vision problems and mood changes. They also may have low iron, called anemia, or low blood counts.

The recommended daily amount of vitamin B-12 for adults is 2.4 micrograms (mcg). Older adults may need to eat more vitamin B-12. The ability to absorb vitamin B-12 lowers as a person gets older. Older adults may need to eat 10 to 12 mcg of vitamin B-12 to get enough of this vitamin.

Research on the use of vitamin B-12 for specific activities and conditions shows:

• Heart and blood vessel disease. People with heart and blood vessel disease, also called cardiovascular disease, may have high levels of a compound called homocysteine. Vitamin B-12 and other B vitamins may help lower homocysteine levels. But researchers haven't found that lowering homocysteine levels lowers the risk of heart and blood vessel disease.
• Athletic performance and increasing energy. There's no proof that taking vitamin B-12 supplements or injections boosts energy or improves athletic performance.

Most people get enough vitamin B-12 from a balanced diet. But older adults and people who follow vegetarian or vegan diets may find it helpful to take vitamin B-12 supplements. People who have conditions that keep them from absorbing nutrients, such as celiac disease or Crohn's disease, also may find that vitamin B-12 supplements are helpful.

Vitamin B-12 supplements also are suggested for women who are pregnant, who are breastfeeding and not using any formula, or who follow vegetarian or vegan diets.

Taking high doses of vitamin B-12 can cause side effects. A person should only take higher doses if a healthcare professional recommends doing this.

When taken at recommended doses, vitamin B-12 supplements are generally considered safe. The recommended daily amount of vitamin B-12 for adults is 2.4 mcg and 10 to 12 mcg for older adults.

Taking doses of vitamin B-12 might cause:

• Headache.
• Nausea.
• Diarrhea.
• Weakness.
• Tingling sensation in hands and feet.

Having vitamin B-12 levels that are too high may raise the risk of getting cancer or breaking a hip.

Possible interactions include:

• Aminosalicylic acid (Paser). Taking this medicine used to treat digestive problems might lower how well the body can absorb vitamin B-12.
• Antiseizure medicines. Taking phenobarbital (Sezaby), phenytoin (Dilantin) or carbamazepine (Tegretrol) to treat seizures might lower how well the body can absorb vitamin B-12.
• Colchicine (Colcrys, Mitigare, Gloperba). Taking this anti-inflammatory medicine used to prevent and treat gout attacks might lower how well the body can absorb vitamin B-12.
• Metformin (Glumetza, Fortamet, others). Taking this diabetes medicine might lower the body's ability to absorb vitamin B-12.
• Gastric acid inhibitors. Taking omeprazole (Prilosec), lansoprazole (Prevacid) or other stomach acid-reducing medicine might lower the body's ability to absorb vitamin B-12.
• Vitamin C (ascorbic acid) supplements. Taking vitamin B-12 with vitamin C might lower the available amount of vitamin B-12 in the body.
• Bile acid sequestrants (cholestyramine). Taking bile acid sequestrants may interfere with B-12 absorption. A healthcare professional might suggest taking vitamin B-12 supplements to avoid the risk of low vitamin B-12 levels.