The word “oral” is derived from the Latin word “os” for mouth and means “concerning the mouth”, “belonging to the mouth”. If dietary supplements are taken orally, this means they are taken through the mouth, in contrast to rectal or parenteral administration. The food supplements are therefore absorbed through the mouth and subsequently swallowed. Oral intake therefore refers to a route of administration. With oral intake, the active substances are sometimes already absorbed through the oral mucosa. In the stomach and small intestine, the active ingredient dissolves and is absorbed through the stomach and intestinal mucosa. Most of the time, however, the active substance only enters the bloodstream in the stomach and intestine. In order to reach the large bloodstream, the active substance has to pass through the liver, the intestinal wall or the lungs. The active substance finally reaches its destination via the blood. Already in the intestinal wall and the liver, many substances are metabolised, chemically changed. In the gastrointestinal tract, other foods can also influence how much and how quickly the respective active substance can be absorbed when taken orally. Since food supplements are food, most are also taken orally, by mouth, in the form of food. When taking them orally, it is important to ensure that the correct dosage is taken. Oral intake is the most common way in which food supplements are taken, the safest and also the easiest. The oral form of intake is the most common way to take an active ingredient in the form of food supplements and food. Another advantage of oral intake is that different human needs can be addressed.