The problem is TIME. Taking 10,000 IU for a medium amount of time will very very likely be fine. But due to fat solubility and therefore slow build up in the b

The problem is TIME. Taking 10,000 IU for a medium amount of time will very very likely be fine. But due to fat solubility and therefore slow build up in the body, you are increasingly growing towards toxic levels over a long time. The body can only regulate vitamin D before synthesis, after sunlight exposure. But if you take already-synthesized vitamin D, that regulation won't kick in and you're free to get hypervitaminosis. Time in combination with individual biology are what brings issues here. Get blood work done (it cost me 30€ in Germany but was combined with 2 other tests).