Nutrition and health expert, New York City nutrition and health expert Samantha Cassetty (Samantha Cassetty, MS, RD) conducted a medical review of this article.
Vitamin B12 plays a key role in many body functions, such as making red blood cells and supporting the nervous system.
Due to the importance of B12, many people choose to supplement it. This is information on the side effects of vitamin B12 supplements you need to take and whether you might take too much information.
Natalie Allen, a clinical assistant professor of biomedical sciences at Missouri State University, said it is highly unlikely that anyone will consume too much B12.
The Institute of Medicine has not determined the upper limit of B12 intake, because studies have shown that excessive intake of B12 through food or supplements has no adverse effects on health.
Medical term: The maximum allowable intake level is the highest nutritional intake level, which will not cause any adverse health effects to most people.
Vitamin B12 is a water-soluble vitamin, which means it is soluble in water and quickly absorbed by the body. Allen said that it is stored in the liver, and any body you do not use will be excreted through urine. Even at high doses, your body can only absorb a portion of B12 supplements. For example, a healthy person taking 500 mcg of oral B12 supplements will only absorb about 10 mcg.
Sheri Vettel, a registered dietitian at the Institute of Comprehensive Nutrition, said that although rare, B12 levels in blood tests may be elevated.
Serum B12 levels between 300 pg/mL and 900 pg/mL are considered normal, while levels above 900 pg/mL are considered high.
If your B12 level rises, your doctor may perform other tests to determine the underlying cause.
Allen said that the side effects of vitamin B12 supplementation are rare and only occur when B12 is injected, rather than oral supplements. Vitamin B12 injections are usually used to treat deficiencies in people who cannot absorb sufficient amounts of B12.
Allen said that the absorption rate of B12 injection is higher than taking supplements, which is why it causes side effects.
The daily recommended amount of vitamin B12 is the same for men and women, but it varies with age. This is a breakdown:
Important note: Pregnant and breastfeeding women need more vitamin B12 to maintain themselves and the growing fetus or breastfeeding newborn. Pregnant women need 2.6 mcg of vitamin B12 a day, while breastfeeding women need 2.8 mcg.
Allen said that most people can get enough vitamin B12 from their diet, so there is no need for extensive supplementation. Some groups may benefit from B12 deficiency or need supplementation. These include:
Although there is no upper limit for the amount of vitamin B12 you can take, there are general dosage recommendations.
For example, the Vegetarian Nutritional Diet Practice Group recommends that vegetarians consider supplementing with 250 mcg of B12 per day.
Before starting any supplement, please discuss your diet and health history with your doctor or registered dietitian to determine which supplements you may need and how much you should take.
The Institute of Medicine has not determined the upper limit of B12 intake, because studies have shown that excessive intake of B12 through food or supplements has no adverse effects on health.
The side effects of B12 supplementation are rare, but may occur when receiving B12 injections. Due to certain conditions that inhibit absorption, some people may need to supplement B12. Discuss with your doctor or registered dietitian whether you should supplement B12 and how much you should take.