Cholecalciferol can be taken as an oral dietary supplement to prevent vitamin D deficiency or as a medication to treat associated diseases, including rickets. It is also used for familial hypophosphatemia, hypoparathyroidism that is causing low blood calcium, and Fanconi syndrome. Vitamin-D supplements may not be effective in people with severe kidney disease. Excessive doses in humans can result in vomiting, constipation, weakness, and confusion. Other risks include kidney stones. Doses greater than 40,000IU (1,000μg) per day are generally required before high blood calcium occurs. Normal doses, 800–2000 IU per day, are safe in pregnancy.