Vitamin D Toxicity

The Canadian Medical Association Journal recently reported a case of a 54-year-old man who developed kidney failure as a result of taking too much Vitamin D

In my naturopathic medicine practice, it’s not uncommon for me to see new patients who are taking various vitamin and nutritional supplements that they purchased over-the-counter based on an article they read. Sometimes they try something new based on the recommendation of a family member, friend or store employee. One of the first things I like to do when I meet with a new patient is conduct a review of all prescription and over-the-counter medications, as well as any nutritional or herbal supplements that they have at home - whether they’re using them regularly or not. People are often surprised and unaware of the potential risks of the natural substances they’ve been taking, or the potential interactions and side-effects of combining various treatments with prescription medications. 

Vitamin D is a very common over-the-counter supplement being used by Canadians. Newspapers, magazines and health bloggers have been touting the benefits of vitamin D for years – telling Canadians that we should be taking more of the vitamin because we don’t get enough winter sunshine here in the True North to make enough of our own.

Vitamin D is generally known to help the body to absorb calcium, and it plays an important role in the maintenance of healthy bones, immune function, and the reduction of inflammation. In addition, researchers have been spending a considerable amount of time over the past decade looking into the real issues of vitamin D deficiency that seems to be impacting populations worldwide.

What most people don’t realize is that the old adage that you CAN have too much of a good thing rings true in the case of vitamin D.  

In dosages over 1000 IU, vitamin D is considered a drug that only certain regulated health professionals can prescribe – in Ontario this includes medical doctors, nurse practitioners, and naturopathic doctors with prescribing authority.  

In addition to having so many health benefits, vitamin D carries with it a real risk of toxicity.  It can cause a buildup of calcium in the blood, which can lead to kidney damage, kidney failure, hearing loss, and other concerning symptoms of toxicity. Once the damage is done, it could take months to resolve, if it resolves at all.  Even more concerning is that those with vitamin D toxicity may go for months without symptoms, in the meantime, their body may have stored so much vitamin D in fat tissue, that it will keep being released in the body for weeks to months after ceasing use of the vitamin.  

To stay on the safe side, you shouldn’t consume vitamin D over 1000 IU, or over several months without checking in with your family physician or naturopathic doctor. If you’ve been taking vitamin D without the guidance of a regulated health professional, it may be time to check-in and have your vitamin D levels tested. 

If you’re taking any other vitamins, herbs or supplements, even if you purchased them over-the-counter, do yourself a favour and check in with any of the following who know you well: your naturopathic doctor, family physician, nurse practitioner or pharmacist so you can get the guidance that’s most appropriate for your individual needs. 


Bourne A.L., Avila-Casado C. & Bargman J.M. (2019). Use of vitamin D drops leading to kidney failure in a 54-year-old man. CMAJ: 191(14): E390-E394.

Holick MF. (2017). The vitamin D deficiency pandemic: Approaches for diagnosis, treatment and prevention. Rev Endocr Metab Disor; 18(2): 153-165.

Olszowiec-Chlebna M. et al. (2019). Vitamin D inhibits pro-inflammatory cytokines in the Airways of cystic fibrosis patients infected by Pseudomonas aeruginosa – pilot study. Intal J. Pediatr; 45(1): 41. 

Scott JF et al. (2018). Oral Vitamin D Rapidly Attenuates Inflammation from Sunburn: An Interventional Study.J Invest Dermatol; 137(10); 2078-2086.

Sylvi Martin