On 13/11/2019, a scientific seminar about vitamin D deficiency and its effects on human’s body held at the CME by assist. Prof. Dr. Asaad Mubarak Jabaar/Internal medicine specialist with the attendance of the teaching staff. The seminar included some points about the sources of the vitamin, its effects on the cells functions, and the diseases related to the deficiency of the vitamin. The seminar aimed at the routes of prevention and treatment of vitamin D deficiency. The vitamin defined as a substance produced by the skin under the influence of the sun. The presence of this vitamin works on maintaining good level of Calcium in the body and good bone health. This vitamin also works on improving the immune system against the infections and cancerous cells.