**10. Vitamin D toxicity and safety limits**

Excessive oral supplementation and food fortification of vitamin D may lead to toxicity because it raises plasma [25(OH)D] concentrations that exceed DBP binding capacity, and free [25(OH)D] concentrations have direct effects on gene expression once it enters the target cells [13].

Upper safe limit is 5000 IU a day (and some considered it to be 10,000 IU), and the toxicity does not manifest serum levels below 120 ng/mL (300 nmol/L). To reach the latter levels, one must ingest vitamin D in excess of 50,000 IU daily for several months. Thus, the safety of doses to 5000 IU a day is assured [4].
