A man developed kidney failure after taking 12 times the recommended amount of vitamin D every day.
The unnamed 54-year-old, from Canada, had been taking the bumper dose drops for two-and-a-half-years after being advised it by a naturopath.
But his health took a turn for the worse when he took a two week holiday and spent eight hours a day sunbathing - exposure to the sun helps the body to produce vitamin D.
Medical tests showed his blood creatinine levels were climbing, which is a sign the kidneys are struggling to work.
Doctors then found a dangerous build-up of vitamin D and calcium in his blood had impaired the function of his kidneys.
A 54-year-old man from Canada developed kidney failure after taking 12 times the recommended dose of a vitamin D supplement
It took a year to get the patient back to health - but he has been left with chronic kidney disease and may need dialysis in later life.
The patient, who did not have a history of bone loss or vitamin D deficiency, took a total of 8,000-12,000IU a day.
The recommended amount for people in Canada is a maximum 1,000IU - four times lower than guidelines for people in Britain.
Doctors, led by Bourne Auguste, a nephrologist at Toronto General Hospital, said they were concerned other people would make the same mistake.
Mr Auguste told Global News: 'He thought that vitamins are harmless.
'And his logic, which one can understand looking back, is that the more vitamin D I take, the stronger the bones will be.'
For unknown reasons, the patient said he was seeing a naturopathic, a specialist that suggests alternative methods such as homeopathy to try and treat illnesses.
She advised the man take eight drops of a brand daily which contained 500IU per drop, according to the report in the Canadian Medical Association Journal.
This would have come to 4,000IU - the maximum that is recommended a day in the UK by the NHS before it could become harmful.
But, unknowingly, the man bought another vitamin D product that contained 1,000IU per drop.
After returning home from a two-week trip to Southeast Asia, he went to his doctor. However, it is unclear why he attended.
His creatinine level had increased from his baseline of 100 μmol/L before the trip, to 132 μmol/L.
Some groups of the population are at greater risk of not getting enough vitamin D. Everyone over the age of five years is advised to consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D, but most people will get enough in the summer.
The amount of vitamin D contained in supplements is sometimes expressed in international units (IU), where 40 IU is equal to 1 microgram (1µg) of vitamin D.
If you choose to take vitamin D supplements, 400 IU a day will be enough for most people.
People who take supplements are advised not to take more than 4000 IU of vitamin D a day, as it could be harmful (this is equal to 100 micrograms or 0.1 milligrams).
This applies to adults, including pregnant and breastfeeding women and the elderly, and children aged 11 to 17.
Children aged 1 to 10 shouldn't have more than 2000
