With a societal push towards wellness, over-the-counter vitamins have become part of the daily routine of millions of people worldwide. Although vitamin supplements are safely consumed by many people every day, it’s possible to take too high of a dose, which can result in adverse side effects. From March 2023, the Therapeutic Goods Administration (TGA) mandated that products containing vitamin B6 in daily doses above 10 mg require a label warning. This previously applied to products containing over 50 mg per daily dose.

Dr Gemma Daley, a consultant Chemical Pathologist at Sullivan Nicolaides Pathology in Brisbane says she has seen an increase in patients presenting with peripheral neuropathy associated with excess vitamin B6 blood levels,

Peripheral Neuropathy

“There has been an increase in people taking over the counter medication in earnest for their own health, not knowing that it could potentially be damaging. Whilst getting enough vitamin B6 is important, typically, you can get enough from your diet, if you regularly eat foods like fish, starchy vegetables, and non-citrus fruits. What people may not know is that vitamin B6 is present in lots of multivitamin and mineral supplements that can be bought in supermarkets, health food shops and pharmacies without a prescription. Excess vitamin B6 is associated with peripheral neuropathy, which can result in tingling, burning or numbness usually in the hands and feet.

“Although the TGA recently reduced the maximum permitted daily dose of vitamin B6 in individual products from 200mg to 100 mg for adults (and less for children depending on their age), peripheral neuropathy can occur at very low doses (less than 50 mg). If people are taking more than one supplement then they may be taking vitamin B6 from multiple sources and the result is cumulative,” said Dr Daley.

Recommended intake of B6

Vitamin B6 (as pyridoxine hydrochloride) is a common inclusion in magnesium supplements, with each tablet containing up to 60 mg. A patient taking two magnesium tablets per day could therefore be unintentionally consuming 120 mg of vitamin B6. This is far greater than the recommended dietary intake of vitamin B6 for adults in Australia and New Zealand of 1.3–2.0 mg/day with a maximum of 50 mg/day.

As pyridoxine hydrochloride has a half-life of up to 30 days, repetitive small doses taken over a period of months can accumulate, resulting in high blood concentrations.

“We get called all the time with these really high levels of vitamin B6. Patients that are taking magnesium are unaware that it can lead to very high levels of B6. They could take a couple of tablets in the morning and in the evening and suddenly they are well over the recommended daily dose. It’s important for people to know what’s in their supplements because it’s often not obvious. It is essential for everyone to read the small print to make sure they are not taking high-dose vitamin B6 accidentally. They should also check the total amount of vitamin B6 they are taking each day,” said Dr Daley.