People take vitamin D3 to improve their overall health and to help the kidneys properly regulate the amount of phosphate in the blood, which encourages the blood to stay at the correct pH level, according to Everyday Health. Doctors may prescribe vitamin D3 to patients with osteoporosis; underactive parathyroid glands, which is a hereditary condition that prevents the body from responding to parathyroid hormones; or low blood phosphate levels.
People may also take vitamin D3 to prevent diseases caused by vitamin D deficiency, such as osteomalacia or rickets, explains Everyday Health. Doctors have tied digestive problems, such as Crohn's, celiac and liver disease, to low vitamin D levels, so people with these conditions may supplement. Some people may take vitamin D3 to improve acne, but there is no scientific proof vitamin D improves skin conditions. Although some people with acne report their skin becomes worse in the winter, researchers believe a lack of sun exposure, not vitamin D itself, causes this issue.
The body produces vitamin D3 when exposed to sunlight, while vitamin D2 is in foods such as salmon, mackerel and egg yolks, notes Everyday Health. Doctors think vitamin D3 is safer to use as a supplement because the body limits the amount of vitamin D3 in the blood more stringently than vitamin D2. People can purchase vitamin D3, also called cholecalciferol, over the counter.