Vitamin B6, B12 and nerve symptoms: too much or too little?

Two useful nutrients, two different risks

Both B6 and B12 are needed for normal body function. Too little available B12 and excessive B6 from supplements are different problems that can produce overlapping nerve symptoms. Neither means that every tingling sensation is caused by a vitamin. Start with what neuropathy means and how it is assessed.23

Sudden weakness or numbness on one side, facial drooping or difficulty speaking can be signs of a stroke. Call your local emergency service immediately, even if the symptoms go away; do not wait to see whether vitamins help.1

How can B12 become too low?

A person may not consume enough B12, or may have trouble absorbing it despite eating foods containing it. For example, pernicious anaemia is an autoimmune condition that interferes with absorption, and Crohn’s disease or stomach surgery can sometimes affect absorption too. Some medicines also affect B12.

Nitrous oxide is a different problem: it can inactivate B12 and cause nerve damage, sometimes even when the blood B12 level is normal. The nitrous oxide and B12 guide explains this risk and when to seek care.

B12 deficiency can cause numbness, tingling, weakness or balance problems even without anaemia. Early assessment matters because some problems may persist if deficiency is untreated. The B12 guide explains food, absorption and treatment questions.2578

What does metformin change?

The UK medicines regulator says metformin can lower B12 levels, particularly with longer use, higher doses or other risk factors. New or worsening tingling, marked tiredness or a sore red tongue can have several causes and deserve medical advice. The UK regulator also recommends that clinicians consider periodic B12 monitoring for people taking metformin who have risk factors for deficiency. Do not stop metformin without discussing it with the prescriber; the regulator notes that B12 can be corrected while metformin continues when appropriate.4

How can a B6 supplement become a problem?

B6 may be present in a multivitamin, a B-complex and a magnesium or zinc product at the same time. The Australian TGA reports that supplement-associated neuropathy has occurred at different amounts and that susceptibility varies. Its review did not identify a minimum amount or duration at which risk begins. This does not establish that every product causes harm or that the same rules apply in every country. Regular dietary B6 from food is a different context. See B6 labels and nerve safety.3

What should I bring to an appointment?

Bring the actual bottles or clear photos of every medicine and supplement label, including serving size, ingredient amounts and how long you have used each product. Note where symptoms occur, when they began and whether they are changing. If you have tingling, burning or numbness while taking B6-containing products, seek prompt advice from a healthcare professional and identify those products; the TGA advises stopping the affected B6 product and seeing a practitioner as soon as possible. Do not independently stop a prescribed medicine without contacting the prescriber.34

Can a blood test give the whole answer?

Blood tests can help, but symptoms, health history and the laboratory result must be considered together. NICE notes there is no single perfect test for B12 deficiency. Tell the clinician if you already take B12: supplements can increase a measured level without fully treating a deficiency. Do not delay needed medical care just to arrange testing. For a closer look at total B12, MMA and other markers, read the B12 testing guide.5

Will extra vitamins repair nerves?

Correcting a documented deficiency is different from taking extra vitamins when there is no deficiency. Some nerve symptoms improve when their cause is addressed, but recovery can be incomplete and depends on the cause and timing. A general “nerve support” label cannot establish that a particular product will help; taking more B6 can add a separate risk. For a different research question, see what ARA-290 studies actually measured.263