Vitamin D3 helps your body absorb calcium, which is essential for healthy bones. Direct sunlight, foods like fatty fish and fortified dairy, and supplements are good sources of Vitamin D3 Cholecalciferol, also known as vitamin D3, colecalciferol or calciol, is a skin-made vitamin D that is found in certain foods and used as a dietary supplement. [3] It was first described in 1936, [4] and is on the World Health Organization's List of Essential Medicines. [5] Several forms (vitamers) of vitamin D exist, with the two major forms being vitamin D 2 (ergocalciferol), and vitamin D 3 (cholecalciferol). [1] The common-use term vitamin D refers to both D 2 and D 3, which were chemically characterized, respectively, in 1931 and 1935. Home › Vitamin D › Dosage Guide Vitamin D3 Dosage 2026: How Much Should You Take? By Erin Rose · Published March 15, 2026 · Updated August 27, 2026 · Methodology The recommended amount of vitamin D for adults is 600 IU (15 mcg) a day up to age 70, and 800 IU (20 mcg) from 71. The daily ceiling is 4,000 IU. Taking a vitamin D supplement or a multivitamin with vitamin D may help improve bone health. The recommended daily amount of vitamin D is 400 international units (IU) for children up to age 12 months, 600 IU for people ages 1 to 70 years, and 800 IU for people over 70 years. Vitamin D3 is important for brain health, strong bones, and anti-cancer properties. Learn which 5 foods to eat to get more Vitamin D3. Vitamin D3 helps your bones by improving calcium and phosphorus absorption. Low vitamin D3 levels can affect your mood and lead to feelings of sadness or anxiety. Vitamin D3 boosts your immune system by helping fight infections and controlling inflammation. Cholecalciferol is vitamin D3. Vitamin D helps your body absorb calcium. Vitamin D is also essential for maintaining a healthy immune system. The function of the immune system is to prevent or limit infection. Cholecalciferol is used as a dietary supplement in people who do not get enough vitamin D in their diets to maintain adequate health. Vitamin D3 is essential for strong bones, immunity, and overall health; learn about its benefits, dosage, deficiency symptoms, food sources, and safe usage. Vitamin D deficiency means that you don’t have enough vitamin D in your body. It's common and primarily causes issues with your bones and muscles.