Skip to content Too much vitamin D can cause calcium levels in the blood to rise, a condition known as hypercalcemia. Possible symptoms include persistent thirst, frequent urination, nausea, vomiting, poor appetite, constipation, dehydration, weakness, and confusion. In more serious cases, high calcium levels may contribute to kidney stones, kidney damage, abnormal heart rhythms, and other complications. These symptoms can also have many other causes, so they do not automatically mean vitamin D toxicity.
