It is well-known that the vast majority of Americans suffer from low levels of vitamin D, a fat soluble nutrient that can be toxic at higher doses.

A study in the Mayo Clinic Proceedings analyzed data from 20,308 subjects. A vitamin D level of 50 ng/mL was considered high.

The researchers found that even with those with high levels of vitamin D, there were very few signs of toxicity — or elevated serum calcium levels.

I have been measuring and prescribing vitamin D for more than 20 years. I have seen little toxicity with supplementation in the range of 3,000 to 10,000 IU per day.

However, because vitamin D is fat-soluble, there is potential toxicity associated with it. The first sign of vitamin D toxicity is an elevated calcium level. This can lead to hypercalcemia, which is associated with muscle aches and pains and kidney stones.

One group of patients that I usually recommend taking higher than usual vitamin D dosing is those suffering from multiple sclerosis. I have seen MS patients significantly improve their extremity weakness with higher than usual vitamin D dosing.

I had a patient named Sue who came to me in a wheelchair. She had a very low vitamin D level — just 3 ng/mL. (Reference range is 30 to 50 ng/mL.) I placed Sue on 50,000 IU of vitamin D3 (the natural form) per day, and measured her vitamin D and calcium levels weekly.

After four weeks, her vitamin D level was more than 100 ng/mL and she felt so good she was able to get up out of her wheelchair.

If you use high doses of vitamin D, I suggest monitoring periodically for elevated calcium levels.