Health supplements containing vitamin B6 can cause peripheral neuropathy
Vitamin B6 (pyridoxine) is in lots of multivitamin and mineral supplements that can be bought in supermarkets, health food shops and pharmacies without a prescription. Many people are not aware that vitamin B6 can cause peripheral neuropathy, which results in tingling, burning or numbness usually in the hands and feet. Taking vitamin B6 even at low doses can cause peripheral neuropathy but people are more likely to get it if they are taking more than one supplement.
The TGA has received over 30 reports of peripheral neuropathy suspected to be related to products containing vitamin B6. This is a known side effect of vitamin B6 but the TGA reports suggest some people are not aware of this and do not realise that vitamin B6 is in many health supplements.
If you are taking one or more health supplements, you should:
- Check if they contain vitamin B6. You should look for all the chemical names of vitamin B6 on the label.
- Check the total amount of vitamin B6 you are taking each day. Although the maximum permitted daily dose in individual products has been reduced 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). It is not yet clear why some people are more prone to this side effect than others.
- Watch out for the symptoms of peripheral neuropathy, such as tingling, burning or numbness in your hands and feet, and stop taking the product(s) if you experience them.
- Talk to your health professional if you have any concerns or questions about peripheral neuropathy or vitamin B products, including whether the benefits of supplemental vitamin B6 outweigh the risk of peripheral neuropathy.
At the age of 65, Susan was a fit and active retiree who looked after her grandchildren twice a week, walked regularly and had a passion for gardening. Then she started feeling tingling and numbness in her feet, which spread to her legs. Eventually she found it difficult to walk.
Susan had been taking a regular magnesium supplement for leg cramps for about 10 years. She had also been taking a multivitamin supplement for the past few years.
Susan’s GP referred her to a neurologist, who diagnosed her with peripheral neuropathy. A blood test also revealed that Susan’s vitamin B levels were 10 times above normal levels.
Susan wasn’t aware that vitamin B6 was linked to peripheral neuropathy and hadn’t realised that her daily magnesium supplement contained vitamin B6. When she looked at the label of her magnesium supplement, she saw it contained 40 mg of pyridoxine hydrochloride which is one of the chemical names for vitamin B6 that her neurologist has told her to look out for. She checked the label of her multivitamins and saw that they also contained pyridoxine hydrochloride.
After stopping both supplements, Susan’s symptoms began to improve within a few weeks.
Is this link a new discovery?
No, it has been known for some time that vitamin B6 can cause peripheral neuropathy. We published a safety advisory on peripheral neuropathy and vitamin B6 in May 2020.
However, the TGA has continued to receive adverse event reports that suggest some people are not aware that vitamin B6 can cause peripheral neuropathy and do not realise this vitamin is in many health supplements, including multivitamin and mineral preparations.
Many of the reports involved people who were taking more than one supplement that did not have a warning about this risk on the label. This is because until recent changes to the labelling regulations, a product containing a daily dose of vitamin B6 less than 50 mg did not have to have a warning on the label.
What is peripheral neuropathy?
Peripheral neuropathy is a type of nerve damage that causes tingling, burning or numbness in the body’s extremities, usually the hands or feet. There are many different causes of neuropathy – one of the most common is diabetes.
Peripheral neuropathy is also a known risk with higher doses or prolonged use of vitamin B. In someone with peripheral neuropathy related to vitamin B6, continuing to take the vitamin can make these symptoms worse.
About vitamin B6
Vitamin B6 is a water-soluble nutrient found in food. In this form, it does not cause peripheral neuropathy.
However, vitamin B6 is commonly present in products such as multivitamin and mineral preparations and vitamin B complexes, often in combination with magnesium or zinc.
There are currently more than 1500 medicines in Australia that contain vitamin B6. Most of these are health supplements that can be bought in supermarkets, health foods stores and pharmacies without a prescription, also known as listed medicines.
Other names for vitamin B6
There are 3 forms of vitamin B6 available in products, and often these chemical names will be used on the labels:
- pyridoxine hydrochloride
- pyridoxal 5-phosphate
- pyridoxal 5-phosphate monohydrate.
Pharmaceutical companies must list these names on the label but are not always required to include the common name ‘vitamin B6’.
That’s why you need to look for all of these names to work out how much vitamin B6 you are taking.
New labelling and use regulations
WARNING - Stop taking this medication if you experience tingling, burning or numbness and see your healthcare practitioner as soon as possible. (Contains vitamin B6)
Until recently, only products containing daily doses of vitamin B over 50 mg required a warning about symptoms of peripheral neuropathy and included ‘Contains vitamin B6’ on the label.
The TGA has now updated regulations for listed medicines as follows:
- products containing a daily dose of vitamin B6 above 10 mg require a warning about peripheral neuropathy
- the maximum permitted daily dose of vitamin B6 in individual products has been reduced from 200 mg to 100 mg for adults, with lower daily dose limits for children, depending on their age
- products containing vitamin B6 must comply with these new requirements after 1 March 2023.
The TGA continues to look for any new evidence and reports of adverse events related to vitamin B6 and peripheral neuropathy, and to monitor whether the new labelling and use requirements are effective.
Why TGA made these labelling and use changes
After receiving over 30 reports of peripheral neuropathy with enough information to indicate a possible link with products containing vitamin B6, the TGA conducted a review and found that:
- peripheral neuropathy can occur at doses of vitamin B6 less than 50 mg
- peripheral neuropathy can occur when people are taking multiple products containing vitamin B6
- the risk appears to vary between people - no minimum dose, length of use or underlying risk factors were identified.
In many cases, people reported they were not aware they had consumed vitamin B6, as the product they were taking was a magnesium supplement.
Others reported taking multiple products that did not have a label warning about peripheral neuropathy because they each contained a low dose of vitamin B6.
If you want to read more about this issue, a safety advisory on peripheral neuropathy and vitamin B6 was published in May 2020 and a recent article alerting health professionals has also been published.
The safety of commonly used vitamins and minerals. Geraldine Moses. Aust Prescr 2021;44:119-23. 2 August 2021. DOI: 10.18773/austprescr.2021.029
Consumers and health professionals are encouraged to report problems with medicines or vaccines. Your report will contribute to the TGA's monitoring of these products.
The TGA cannot give advice about an individual's medical condition. You are strongly encouraged to talk with your doctor or pharmacist if you are concerned about a possible side effect that you think may be related to a medicine or vaccine.