It's good to take Vitamin D supplement, especially through the winter, and there is strong medical evidence that it can help your immune system to fight infections and viruses.
If it wasn't any good for you I very much doubt my oncologist would be prescribing it!
But don't take them like sweeties, Wully, follow the instructions on the packet or bottle!!!
Bottom Line: The safe upper limit of intake for Vitamin D is set at 4000 IU/day.
Intake in the range of 40,000–100,000 IU/day (10-25 times the recommended upper limit) has been linked with toxicity in humans.
The main consequence of vitamin D toxicity is a buildup of calcium in your blood (hypercalcemia), which can cause nausea and vomiting, weakness, and frequent urination. Vitamin D toxicity might progress to bone pain and kidney problems, such as the formation of calcium stones.