Too much vitamin D3 (cholecalciferol) can lead to vitamin D toxicity, also known as hypervitaminosis D This usually happens from excessive supplementation, not from sun exposure or food. Here are 5 signs that you might have too much vitamin D3 in your system Excess vitamin D can cause your calcium levels to rise too much, leading to digestive symptoms like feeling sick to your stomach & vomiting Ironically, although vitamin D is essential for bone health, too much of it can leach calcium from bones, causing muscle soreness or weakness Frequent Urination and Dehydration High calcium levels (hypercalcemia) can lead to constant thirst or dehydration symptoms like dry mouth or dizziness Too much vitamin D in your body can also cause aches in bones or joints Too much vitamin D can make you feel physically tired or weak or mentally foggy or low in energy