An unexpected overdose
It all began with tingling in my feet that wouldn’t go away.
What followed were visits to eight specialists here in Hong Kong, from neurologists to an orthopedist to an endocrinologist. They were befuddled by my symptoms as all of my tests, including MRI scans and nerve-conduction studies, had come back normal.
“Sorry,” they said repeatedly, “but from my end I can’t find a cause.”
In the meantime, I was having difficulty falling asleep or even sitting for extended periods of time. The worst thing was the mental distress from not knowing what was wrong.
A diagnosis finally came three months after the tingling first emerged, when results from a blood test showed I had Vitamin B6 toxicity. My general practitioner had picked up on the possibility when I mentioned a “yellow pill” I had been taking, and subsequent tests showed the amount of Vitamin B6 in my blood was 144 nanograms per milliliter, seven times the upper range referenced by Quest Diagnostics.
An overdose can cause peripheral neuropathy, a condition characterized by nerve tingling, numbness or pain, typically in the limbs.
So how did my B6 levels get so high?
Every day for two months before my feet began tingling, I took a Vitamin B complex pill given to me by a doctor of traditional Chinese medicine, who I was seeing to manage a thyroid goiter. Each one contained 50mg of B6. I also occasionally bring an immunity-boosting Vitamin B drink on reporting trips, containing 10mg of B6 per tablet.
The exact dose-response relationship and the mechanism of how Vitamin B6 overdose can lead to neuropathy hasn’t been clearly established, and the condition isn’t well known among healthcare professionals. But medical authorities are increasingly taking note.
Last year, the European Food Safety Authority set a new tolerable upper intake level for B6 of 12.5 mg a day, with neuropathy the “critical effect” on which the new limit is based. In Asia, Singapore advised that health care professionals can consider reviewing both the dose and duration of vitamin B6 intake — including over-the-counter health supplements — by patients presenting with symptoms of peripheral neuropathy.
Once it’s diagnosed, there’s nothing much one can do to expel Vitamin B6 from the body but to patiently wait. I joined a Facebook support group for people with B6-induced neuropathy, one of the few resources available for people in my shoes. The group recommends a low-B6 diet, hydration and exercise. I learned from other members that some patients can go years without knowing the cause of their ailment, and are often prescribed even more Vitamin B supplements, given that the symptoms of overdose and deficiency are similar.
Today, my symptoms have ceased and my latest B6 levels are in the normal range. This ordeal, crazy as it’s been, has also offered some bigger life lessons — like the importance of keeping active, sleeping enough and eating well before turning to supplements. —Krystal Chia
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