i was once accidentally taking 25.000 IU daily for a few months instead of 5.000 (400-600 IU being official recommended dosages, although many sources claim that that's way to little, hence the 5.000). went to an endocrinologist for really weird bouts of whole body weakness and exhaustion after even light activity. nothing like i had ever experienced. lab results came back with a vitamin d level of the maximum measurement level (so probably more, maybe a lot more). that's when i realized i was taking 5 times more than i had planned. i looked up vitamin d toxicity and found fatigue and muscle weakness as symptoms and had the answer to my condition. i don't want to know what would have happened if i hadn't looked it up myself, because the doctor didn't even want to see me again, claiming by letter that my blood work was just fine. so yeah, pay attention to your supplement regime.