Are High Doses of Vitamin B6 Really Dangerous?

Vitamin B6 is one of a group of eight B-vitamins that is essential for good health. It plays a major role in everything from movement to memory to energy expenditure and blood flow. If you are among the 24 percent of Americans who are unable to get sufficient vitamin B6 from your diet, you may need to take a supplement. Although B6 supplements are useful for treating many conditions, taking excessive amounts can put you at risk for vitamin B toxicity.

Your body needs vitamin B6, or pyridoxine, to carry out more than 100 enzyme reactions involved in various functions, including the utilization of carbohydrates, fats and proteins. Vitamin B6 benefits a range of physical, psychological and metabolic processes, the most well-known relating to your nervous system.

Vitamin B6 supplements are often used, not only to ​reverse a deficiency​, but for the treatment of a number of conditions, including premenstrual syndrome, carpal tunnel, childhood autism, schizophrenia, attention deficit and hyperactivity disorder, morning sickness and certain types of anemia.

​Read more:​ List of B-Complex Vitamins

Your body cannot synthesize vitamin B6, so you need to ensure your diet supplies enough of the nutrient every day. Because many ​foods are fortified​, it's easy to meet your daily requirements if you eat a balanced diet. ​Meat is the best source​ of vitamin B6 because it has a better bioavailability than plant-based sources, according to a paper published in StatPearls in 2019.

Choose from the following vitamin B6-rich foods:

• Beef, including organ meats
• Fish and seafood
• Chicken, turkey and other poultry
• Potatoes and other starchy vegetables
• Fruit and dried fruit, with the exception of citrus
• Nuts
• Legumes
• Fortified foods, such as breakfast cereal and energy bars

Dietary supplements are usually in the form of pyridoxine hydrochloride. Absorption of vitamin B6 from supplements is similar to that from food sources. Vitamin B6 comes as an individual supplement or combined with other vitamin B supplements in B-complex. Many multivitamins and herbal remedies containing B6 are sold over-the-counter for everyday use.

You can take B6 supplement in an oral form, including tablet, caplet, chewable, powder or liquid forms. Vitamin B6 can also be administered sublingually or by injection.

In some cases, a vitamin B6 deficiency may warrant the use of vitamin B6 supplements due to your body's inability to properly ​absorb nutrients​. Some of these situations include:

• Being a vegetarian, vegan or having a restricted diet
• Being elderly with a reduction of stomach acid
• Having an autoimmune disorder, such as rheumatoid arthritis
• Having a medical condition that impairs absorption, such as Crohn's, celiac, inflammatory bowel disease, colitis or autoimmune disorders
• Being a chronic alcoholic
• Having kidney disease or poor renal function

​Read more:​ The Definition of Food Supplements

For good health, the Institute of Medicine recommends a​ daily allowance​ for vitamin B6, according to age and gender.

• Ages 1 to 3 years: 0.5 milligram
  
• Ages 4 to 8

years

: 0.6 milligram

• Ages 9 to 13

years

: 1.0 milligram

• Ages 14 to 18

years

: 1.2 milligrams for girls; 1.3 milligrams for boys

• Ages 19 to 50

years

: 1.3 milligrams

• Ages 51 and older: 1.7 milligrams for men; 1.5 milligrams for women
• Pregnant women: 1.9 milligrams
• Lactating women: 2 milligrams

It is unlikely you could get an overdose of vitamin B6 from food, but taking supplements that have a high vitamin B6 content may cause adverse effects. For this reason, an ​upper limit for vitamin B6​ has been set as a guideline to help keep your dosage safe. This amount applies to both food and supplement intakes. These amounts are:

• Ages 4 to 8 years: 40 milligrams
• Ages 9 to 13

years

: 60 milligrams

• Ages 14 to 18

years

: 80 milligrams

• Ages 19 and older: 100 milligrams

When taking B6 supplements, even in small and recommended doses, be aware that many people experience some common, mild side effects that include:

• Nausea
• Headache
• Fatigue or drowsiness
• Mild numbness or tingling

​Read more:​ Vitamin Toxicity Symptoms

The amount of vitamin B6 in individual supplements often ranges from ​5 to 500 milligrams​ per tablet. This could result in overly high B6 levels in some cases, especially if you take the supplement over a ​prolonged period​ of time.

Vitamin B6 is water soluble, so excesses are normally excreted in your urine. However, through supplementation, you might take vitamin B6 in a quantity and frequency that does not allow your body to expel it quickly enough. A study published in Poster in 2015 warns of the potential of vitamin B toxicity in levels exceeding even ​50 milligrams​ per day taken long-term.

High vitamin B6 doses are often prescribed for certain medical conditions and metabolic diseases. Linus Pauling Institute reports that ​sensory neuropathy​ often develops at doses of vitamin B6 in excess of ​1,000 milligrams​ per day. Some case reports found severe ​nerve damage​ at doses of less than ​500 milligrams​ per day taken over a period of months.

Excessively high doses of vitamin B6 taken over an extended period of time can result in symptoms similar to those of a ​vitamin B6 deficiency​. Both deficiency and toxicity may cause changes in the blood, heart, skin and gastrointestinal and neuronal cells, according to a study published in Toxicology in Vitro in 2017.

National Institutes of Health reported cases of dangerous toxicity resulting from taking ​1 to 6 grams​ of vitamin B6 for a lengthy period of time. But lower doses, such as ​100 to 300 milligrams ​prescribed daily for alleviating depression can also be a potential danger. Symptoms of toxicity may include:

• Nerve damage causing lack of muscle control and coordination
• Burning pain, numbness, tingling and weakness present in the areas covered by gloves or stockings (often described as having a "glove and stocking" distribution)
• Painful, disfiguring skin lesions
• Sensitivity to light
• Nausea and heartburn and other gastrointestinal issues
• Decreased feeling of ability to feel vibration, pain or extreme temperatures

Symptoms can be very dangerous and debilitating, depending on the ​dosage.​ A study published in the journal Neurology in 2018 reported that symptoms of nerve damage from vitamin B6 toxicity were ​reversible​ over time when the patient discontinued the vitamin B6 supplement and underwent a follow-up of intensive physiotherapy