It's true. Google cholecalciferol (the fancy name for Vitamin D) and pesticide. The same Vitamin D that is in your supplements is used to bait mice and rats and kill them. Yes the dose matters. You can have low Vitamin D and it can impact your bone health, but the "experts" are still arguing over what the magic number is for Vitamin D levels and which test is best. What concerns me is that people apply the logic that if a little is good, a lot must be better and then they take high daily doses of synthetic Vitamin D not realizing there can be negative effects (remember the rats). I am concerned they may be causing more harm than good. Vitamin D pulls calcium from the digestive tract and other tissues into the blood. If you pull too much calcium into the blood it's called Hypercalcemia. Hypercalcemia can lead to abdominal pain, kidney stones, bone loss and bone pain, impaired cognitive function, depression, abnormal heart rhythm, and cardiac arrest. This is why high dose Vitamin D can kill rodents. I have said it before and now I will say it again. You should be getting your vitamins from high quality plant and animal foods, and supplements made from them, not synthetic vitamins. You should also be consulting with someone who is well educated about vitamins, nutrition, and human biochemistry, about your supplements. I am biased but I think a Naturopathic Doctor, Chiropractor, or Osteopathic Physician are likely your best bets for that kind of information. Although, many of them will still recommend high doses of synthetic vitamins so choose carefully. I do not recommend ANY commercially available calcium or Vitamin D supplements. I look at blood work, find out if you have any deficiency symptoms and perform simple tests to determine if you need help balancing your calcium levels and then recommend food based solutions not rat poison.