Q: I have osteoporosis, and my doctor wants me to take 1,000 IU daily of vitamin D, along with my other daily vitamins, which also contain vitamin D. I calculate that this would bring my daily vitamin D total to 2,300 IU. Is this safe?

Answer :Its true that vitamin D can be toxic at extremely high levels and, technically, your total intake would be above the 2,000 IU daily Tolerable Upper Intake Level (UL) for vitamin D set by the Institute of Medicine. An expert panel is currently reviewing the recommended levels for vitamin D, however, and may recommend raising the UL as well as the Adequate Intake (AI); those recommendations are expected next year. Recent clinical trials suggest that the safe upper limit for vitamin D may be as high as 10,000 IU daily. Our advice in the meantime? Make sure your doctor knows about the other supplements youre taking, and see if she thinks you should switch to a lower-dose vitamin D supplement. (For more on vitamin D, see our June 2009 Special Report.)