The U.S. Institutes of Medicine (IOM) set the daily tolerable upper intake (UL) for all vitamins and minerals. The UL is considered to be the maximum level of the nutrient you can take every day (from both foods and supplements) that should not cause any health problems. The IOM sets the UL for vitamin B-6 based on ages:
- Children ages 1 to 3 years: 30 milligrams per day
- Children ages 4 to 8 years: 40 milligrams per day
- Children ages 9 to 13 years: 60 milligrams per day
- Teens ages 14 to 18 years: 80 milligrams per day
- Adults ages 19 and up: 100 milligrams per day
According to the U.S. Office of Dietary Supplements, taking large doses of vitamin B-6 every day for a prolonged time may cause severe and progressive sensory neuropathy characterized by a loss of control of bodily movements.
The nerve damage has been reported in people who have taken one to six grams of pyridoxine for more than one year. The damage is reversible when supplementation is stopped. Vitamin B-6 toxicity can also cause skin lesions, light sensitivity and gastrointestinal symptoms, such as nausea and heartburn.
Why Would Someone Take Large Doses?
A vitamin B-6 deficiency is rare. In the past, vitamin B-6 supplements had been recommended in large doses for treatment of health issues such as carpal tunnel syndrome, premenstrual syndrome (PMS) and for the reduction of homocysteine (a protein that is often elevated when a person is at a high risk for heart disease or dementia).
Unfortunately, scientific studies don't indicate that taking vitamin B-6 relieves either of those syndromes, and although taking vitamin B-6 supplements will reduce homocysteine levels, it doesn't appear to reduce your risk of cardiovascular disease or improve cognitive function.
Vitamin B-6 may be able to help reduce nausea and vomiting in pregnant women. The typical dosage is well below the UL, usually in the range of 10 to 25 milligrams per day. However, even at these safe levels, you should speak to your doctor before taking vitamin B-6 supplements.
Institutes of Medicine, National Institutes of Health. "Dietary Reference Intakes: Vitamins." Accessed July 24, 2012. http://iom.edu/~/media/Files/Activity%20Files/Nutrition/DRIs/DRI_Vitamins.pdf.
LeBlanc KE, Cestia W. "Carpal tunnel syndrome." Am Fam Physician 2011 Apr 15;83(8):952-8.
Marti-Carvajal AJ, Sola I, Lathyris D, Salanti G. "Homocysteine lowering interventions for preventing cardiovascular events." Cochrane Database Syst Rev. 2009 Oct 7;(4):CD006612.
Office of Dietary Supplements, National Institutes of Health. "Dietary Supplement Fact Sheet: Vitamin B6." Accessed July 24, 2012. http://ods.od.nih.gov/factsheets/vitaminb6/.