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Bourne Auguste
Dr. Bourne Auguste, Clinical Fellow in the Home Dialysis Program, Nephrology, examined the 54-year-old man who took high doses of vitamin D over two years, resulting in kidney failure. (Photo: Dr. Bourne Auguste)

An unusual case study from the Nephrology Clinic of Dr. Joanne Bargman at Toronto General Hospital (TG) has shown that excessive amounts of vitamin D can lead to kidney failure.

The case study describes a 54-year-old man who had been prescribed a high dose of vitamin D by a naturopath. He did not have any prior fractures or documented vitamin D deficiency.

Not finding the specific brand prescribed by the naturopath, the patient substituted another one that had a higher concentration of Vitamin D. Over two years, he took eight to 12 drops of vitamin D daily – for a total dose of 8,000 to 12,000 units a day.  

He now has kidney failure due to high blood levels of calcium leading to deposits of calcium in the kidney tissue. His kidney function is 34 per cent, compared to normal functioning at more than 60 per cent.  

According to Osteoporosis Canada, doses up to 2,000 units daily are safe. They recommend vitamin D doses from 800 to 2,000 units daily for older adults and those at high risk for osteoporosis.

The case is reported in the April 8 edition of CMAJ (Canadian Medical Association Journal) by Drs. Bourne Auguste and Joanne Bargman, Nephrology, TG, and Dr. Carmen Avila-Casado, Pathology, UHN.

"Patients should recognize that vitamin D is a medication, and can be associated with risks, particularly when taken at large doses," says Dr. Auguste, Clinical Fellow in the Home Dialysis Program, Nephrology, and the first author of the case report. "More is not better in this example."​

Symptoms of vitamin D toxicity can include: high blood pressure, confusion and kidney stones.

Dr. Auguste also points out that not everyone might need vitamin D supplements, and that low-risk patients should speak to their physicians about why they are considering taking it.  ​

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