Background: Nutritional supplements have many benefits for the human body. Nutritional supplements help maintain body health and body balance in the event of a difference in balance. However, nutritional supplements may affect the human body if misused, especially if a person uses many doses of these vitamins, as they negatively affect the human body and may cause many health problems.

Objectives: to assessment of the knowledge, attitude and practices of patients about the use of nutritional supplements and their effects on body health

Materials & procedures: A descriptive cross-sectional study was conducted in the city of Baghdad in outpatient clinics in order to assess the knowledge, beliefs and practices of patients about the use of nutritional supplements. Data were collected by means of a questionnaire designed for this purpose. Patients were interviewed after taking oral approvals from patients attending outpatient clinics. Data collection continued for a period of four months from the date of 2/2/2023 until 2/6/2023.

Results: the study revealed that (71%) take vitamins and was taking them with a prescription (85%). Vitamin D was found to be the most popular (63%), vitamin E (78%), and vitamin C (46%). The least known is vitamin K (34%). The source of their information about nutritional supplements was from the Internet, friends and relatives. The most important reason for taking nutritional supplements was due to osteoporosis, which reached (78%). And due to pregnancy and childbirth, they reached (46%). And because of maintaining health and healing from diseases.

Conclusions: This study shed light on an important issue in the society, especially our Iraqi society, where in the recent period and the development of the means of the Internet such as (Facebook and Instagram). The use of these nutritional supplements without medical prescriptions is being promoted, and people are eager to use them without knowing their harm and impact on the body. Therefore, the media must inform people in general about the correct way to use nutritional supplements, and here comes the role of doctors and health personnel to spread sufficient knowledge about nutritional supplements through conducting educational courses, lectures and seminars and publishing them on the Internet so that people have knowledge about them. These nutritional supplements are used healthily.