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Vitamin B6: overdoses leading to neuropathies

With few exceptions, consuming vitamin B6 in addition to food has no medical justification and can lead to overdoses with peripheral neuropathies.

Vitamin B6 is present in many foods of plant and animal origin. Vitamin B6 deficiencies are rare and cause neuropathies (nerve fibre disorders). Overdoses of vitamin B6 also cause sensory neuropathies, with pain, paraesthesias, numbness in limbs and feet, burning, stinging or itching, and occasionally motor neuropathies. These disorders can be disabling, with progressive coordination disorders, unstable gait and loss of manual dexterity.

The time to onset of these disorders depends on the dose and duration of use. The higher the daily doses of vitamin B6, the sooner the disorders appear. They regress at least partially after stopping vitamin B6, sometimes very slowly, over several months; sequelae have been observed.

Apart from a few very specific medical situations, consuming vitamin B6 in addition to diet is not justified, all the less so in quantities greater than 25 mg per day.

Some patient leaflets do not mention this risk. Patients should be informed of the risks of vitamin overdoses caused by many drugs and food supplements, by the proposed dose units, by the accumulation of several products and by taking these over a long period of time.

©Prescrire 1 January 2020

"Vitamin B6: more cases of neuropathy through chronic overdosing" Prescrire Int 2020; 29 (211): 21-22. (Pdf, subscribers only).

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