6 Symptoms of Vitamin B6 Toxicity to Alert Your Doctor

Vitamin B6 is one of the B vitamins that are important for providing the energy your body needs to function. Although generally considered safe at recommended levels, very high intakes of vitamin B6 from supplements or pharmaceutical products can be dangerous. Use caution with your dosage of vitamin B6 as symptoms of toxicity can range from minor skin reactions to severe neurological damage.

A vitamin B6 deficiency may prompt you to take a supplement, but beware of taking too much. (Image: merc67/iStock/GettyImages)

Function of Vitamin B6

Vitamin B6, also called pyridoxine, acts as a coenzyme in the metabolism and utilization of carbohydrates, fats and proteins in your body. Involved in more than 100 enzyme reactions with a wide variety of functions, vitamin B6 benefits your immune system, protects your heart from cholesterol deposits and prevents the formation of kidney stones. Vitamin B6 is also required for normal brain function and development.

Sources of Vitamin B6

Your body cannot store vitamin B6, so you must supply it daily from the food you eat. You can usually get sufficient amounts of vitamin B6 from your diet. In the U.S. many foods are fortified, including cereals and power bars.

Bioavailability of vitamin B6 from natural sources is estimated to be 75 percent from a varied diet. A paper published in StatPearls in 2019 reported that meat sources have a higher bioavailability for B6 than plant-based sources. Foods naturally rich in vitamin B6 provide about 0.25 to 1 milligram of B6 per serving, according ConsumerLab.com. Some foods containing vitamin B6 include:

  • Fish, including tuna and salmon
  • Poultry, including chicken and turkey
  • Meat, including organ meats
  • Starchy vegetables such a potatoes
  • Fruit, other than citrus

Dietary Recommendations

For optimum health, you should strive to meet the recommended daily allowance for vitamin B6 set by the Institute of Medicine as follows:

Although there are no recorded adverse outcomes from a high intake of vitamin B6 from food, larger doses from supplements have been shown to cause vitamin B6 overdose symptoms. For this reason, an upper limit for vitamin B6 has been established:

Reasons You May Need a Supplement

Pyridoxine is used not only to treat and prevent vitamin B6 deficiency. It is also prescribed for a number of conditions, including the treatment of premenstrual syndrome, childhood autism, carpal tunnel syndrome, schizophrenia and attention-deficit hyperactivity disorder, all with varying results.

If you're at risk of a deficiency in vitamin B6 due to inadequate intake or increased metabolic requirements that cause low levels of B6, you may require a dietary supplement. Some of these situations may include:

  • Restricted diet, such as vegetarianism
  • Poor renal function or kidney disease
  • Autoimmune disorders, such as rheumatoid arthritis, with inflammation causing low levels of vitamin B6
  • Medical conditions that impair absorption, including Crohn's, celiac, inflammatory bowel disease, colitis and autoimmune disorders
  • Chronic alcohol dependence
  • Reduction of stomach acid, especially in older individuals
  • Certain genetic diseases, such as homocystinuria
  • Recovery from surgery, such as for weight loss, gastric bypass or removal of part of the small intestine
  • Obesity

Medications that interfere with gastrointestinal absorption, including some anti-seizure drugs or proton pump inhibitors, may also require supplementation. Oral contraceptives can also deplete several B vitamins, according to University Health News.

Toxicity From Supplements

Vitamin B6 is available in multivitamins, in supplements combined with other B vitamins (referred to as B-complex) and as an individual supplement, commonly in the form of pyridoxine. Vitamin B6 supplements can be taken in an oral pill, liquid capsule or chewable and sublingual forms. Absorption of vitamin B6 from the various forms of supplements is similar and does not differ significantly from absorption from food sources.

Supplements taken orally are available without a prescription. Prescribed doses and injectable forms of this medicine must be given by a healthcare professional.

Supplements typically range in dosage from 5 to 500 milligrams per tablet. Although excess vitamin B6 is normally excreted in your urine, long-term supplementation with amounts exceeding 50 milligrams per day for prolonged duration may be harmful.

Doses in excess of 1,000 milligrams per day of pyridoxine may lead to toxicity that could result in painful neurological symptoms, known as sensory neuropathy.

The Linus Pauling Institute reports that some individuals have developed sensory neuropathies at daily doses of less than 500 milligrams (taken to treat carpal tunnel syndrome or premenstrual syndrome) over a period of months. No evidence of sensory nerve damage has been reported with intakes below 200 milligrams of pyridoxine daily.

Symptoms of B6 Toxicity

Along with its needed effects, vitamin B6 supplements may cause some unwanted outcomes. Even with small doses, some side effects may result. If any do occur, you should seek medical attention, according to Drugs.com. These include:

  • Nausea
  • Headache
  • Drowsiness
  • Mild numbness or tingling

Prolonged high doses of vitamin B6, leading to toxicity, produce similar symptoms to a vitamin B6 deficiency, according to a study published in Toxicology in Vitro in 2017. Vitamin B6 deficiency and toxicity often involve changes in the blood, skin, heart, gastrointestinal and, especially, neuronal cells.

The National Institutes of Health warns that taking 1 to 6 grams of vitamin B6 for an extended period of 12 to 40 months can result in serious symptoms of:

  • Nerve toxicity that causes lack of muscle control and coordination
  • Burning pain, numbness, tingling and weakness of the hands and feet in a stocking-glove distribution, according to the Merck Manual
  • Painful, unsightly skin patches or disfiguring skin lesions
  • Sensitivity to light
  • Gastrointestinal problems, including nausea and heartburn
  • Decreased sense of touch, inability to feel vibration, pain or extreme temperatures

The severity of symptoms can be debilitating depending on the dosage_._ When the B6 supplement is discontinued, a recent study has shown evidence that symptoms are potentially reversible, as published in the journal Neurology in 2018.

Precautions and Warnings

Ask your doctor or pharmacist if it is safe for you to use vitamin B6 if:

  • You have any medical conditions.
  • You take medications or herbal products.
  • You are allergic to any drugs or foods.

Inform your doctor if you have heart or kidney disease to make sure you can safely receive injectable vitamin B6.

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