The recommended daily allowance of vitamin D for people ages one to 70 is 600 international units (IU) daily, according to Mayo Clinic. This includes pregnant or lactating women. People 71 and older need 800 IUs daily, and most people can get a daily dose of vitamin D by exposing their skin to sunlight each day.
When used to treat specific ailments or diseases, vitamin D dosages vary, notes Mayo Clinic. For example, some doctors order 2,000 IUs of vitamin D with 390 milligrams of calcium lactate for the treatment of osteomalacia that results from the use of anti-seizure drugs. To prevent cancer, some experts recommend taking up to 1,100 IUs of the vitamin daily or up to 2,000 IUs for the treatment of heart disease.