Too Much Vitamin B-12 Side Effects: Rapid Heartbeat

Vitamin B-12 is a general term used to describe a related group of nutrients called cobalamins. Doctors consider B-12 to be safe, and you won't typically develop a rapid heartbeat even if you take large doses of the vitamin. However, you can develop a rapid heartbeat if you have a vitamin B-12 deficiency.

Basics

Cobalamins get their name because they contain significant amounts of the mineral cobalt. Two forms of these nutrients, 5-deoxyadenosylcobalamin and methylcobalamin, are biologically active in human beings. Supplemental forms of vitamin B-12 typically contain a form of cobalamin called cyanocobalamin, which gets converted into methylcobalamin and 5-doxyadenosylcobalamin inside the body. Food sources of B-12 are primarily animal-based and include trout, beef, salmon, pork, chicken, milk and milk products. Vegetarians and vegans can get B-12 in their diets by consuming fortified breakfast cereals and fortified nutritional yeast.

Lack of Harm

Nutrient intake guidelines in the U.S. are set by the National Academy of Sciences' Institute of Medicine, or IOM. According to the IOM, vitamin B-12 does not cause rapid heartbeat or any other harmful side effects when consumed at normal levels by healthy individuals, whether in food or supplement form. Additionally, no harmful side effects are associated with high or excessive B-12 intake. For this reason, the IOM has not established an upper limit for the amount of B-12 you can take in a single day. Normally, upper intake limits act as guidelines for the amount of any nutrient you can take without harming your health.

B-12 Deficiency Effects

You can potentially develop an abnormally rapid heartbeat if you have a deficiency of vitamin B-12 and another B vitamin called folate, according to the American Association for Clinical Chemistry's Lab Tests Online. You can also develop pounding or racing sensations called heart palpitations. Typically, these symptoms are related to the primary effects of B-12 and folate deficiency, which include changes in your gastrointestinal system, nerve damage and a red blood cell disorder called anemia. Additional potential symptoms stemming from these primary effects include dizziness, diarrhea, confusion, paranoia and shortness of breath.

Considerations

Adults and children over the age of 14 need 2.4 mcg of vitamin B-12 a day from various sources, while children between the ages of 9 and 13 need 1.8 mcg. Younger children have lower needs that vary according to their age, while pregnant and lactating women have slightly higher needs than other adults. Although you typically won't develop any problems if you take large amounts of B-12, the IOM does not rule out the possibility of harmful effects associated with excessive consumption. It simply notes that no harmful effects have been established. Consult your doctor for more information on vitamin B-12 intake.