Too much Vitamin D is extremely rare, but it can happen and should be avoided. Learn about high levels of
Vitamin D here.

Too Much Vitamin D

Vitamin D can be harmful if taken in excess. Vitamin D intoxication is extremely rare but can be caused by accidental or intentional intake of high doses of vitamin D. The amount of vitamin D that causes vitamin D toxicity is more than 4 times the amount that adults get naturally through exposure to sunshine. Most reports of vitamin D toxicity have been as a result of mistakes in vitamin D manufacturing facilities, or errors in medically dosing with prescription vitamin D.

Symptoms and consequences of Vitamin D toxicity:

High doses of vitamin D can lead to high levels of calcium in the bloodstream. This is known as hypercalcemia.
Hypercalcemia is an elevated calcium level in the blood. (Normal range: 9-10.5 mg/dL or 2.2-2.6 mmol/L). It is usually an elevated laboratory finding with few symptoms. Therefore, people with hypercalcemia may not feel that anything is wrong and may only find out about their condition with a lab test which can be prescribed by a physician.
Even though hypercalcemia may not have noticeable symptoms, there are important consequences that need to be considered. For example, high levels of calcium can result in anorexia, chills, constipation, confusion, depression, fever, fatigue, increased urination, nausea, pancreatitis, thirst, vomiting and weight loss.
True vitamin D toxicity happens when high levels of calcium go undetected, and calcium begins to build up in organs, such as the kidneys, causing renal or bladders stones.
In order to produce hypercalcemia, most adults would have to take more than 10,000 IU daily for many months or years. Cases of hypercalcemia while taking 10,000 daily for several months have not been reported in published literature.
Most patients with vitamin D toxicity recover fully after discontinuing the vitamin D supplement and avoiding sun exposure for a certain amount of time.

How much is too much?

The following summarize the facts for adults:

The current safety limit for vitamin D supplements in adults is 2,000 IU (50ug)

Review of the literature shows the lowest dose of vitamin D proven to cause toxicity in adults is 40,000 IU/day for many months

Farmers and lifeguards, who are exposed to long periods of sunlight would manufacture 10,000 IU of vitamin D in their skin daily without the use of sunscreen.³

Some experts believe that the official safety limit is very conservative and not based on current evidence

The following summarizes the facts for infants:
“The Tolerable Upper Intake Level (UL) for vitamin D for infants up to one year of age is set at 25ug (1,000 IU) per day which is based on studies examining the highest intake at which no adverse affects were observed on linear growth.” Note that the UL is defined as the highest continuing daily intake of a nutrient that is likely to pose no health risks for almost all individuals.

Overall, it is best to seek individual advice from an informed healthcare profession who is familiar with vitamin D and your health status. Also, follow the directions on the label of products and notify your healthcare provider if you have concerns.

+ – See Resources

¹Cannell J., Hollis BW, Zasloff M, Heaney RP. Diagnosis and treatment of vitamin D deficiency. Expert Opin Pharmacother. 2008; 9(1);1-12.
²Standing Committee on the Scientific Evaluation of Dietary Reference Intakes: Dietary reference intakes: calcium, phosphorus, magnesium, vitamin D and fluoride. National Academy Press, 1997.
³Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations and safety. Am J Clin Nutr. 1999; 69; 842-856
⁴Hathcock JN, Shao A, Veith R, Heaney R. Risk assessment for vitamin D. Am J Clin Nutr. 2007; 85; 6-18 ⁵Vitamin D supplementation for breastfed infants 2004. Health Canada recommendation document (p3)