Is your doctor telling you that you are taking too much vitamin D?
The chart below, based on a review published by Hathcock et al., shows the incidence of vitamin D toxicity in relation to daily vitamin D intake (up to ten million IU per day). The blue circles represent pharmacological studies using doses of up to 50,000 IU vitamin D per day. The red triangles represent cases in which vitamin D intoxication occurred, the intake was known, and the 25(OH)D level was measured. No toxicity was observed at levels below a 25(OH)D serum level of 200 ng/ml (500 nmol/L), and no toxicity was observed in studies reporting a daily vitamin D intake below 30,000 IU.
Due to the wide range of responses to supplementation some individuals will require a daily dose greater than 4,000 or even 10,000 IU/day to reach the recommended range of 40-60 ng/ml. As long as their 25(OH)D serum level is monitored and remains within a healthy range, they should be able to safely continue to take the dose necessary to maintain that level. Individuals with certain conditions, such as primary hyperparathyroidism, sarcoidosis, tuberculosis, and lymphoma, may be hypersensitive to vitamin D supplementation.
For more information, refer to Risk assessment for vitamin D, published by Hathcock et al. in the American Journal of Clinical Nutrition in 2007.