On the one hand, creatine is absorbed via the food (meat, fish, supplements) and on the other hand is formed by the body itself in the pancreas, liver and kidneys and stored in the muscles. The body can only store a certain amount of creatine. The amount stored in the human body is about 120-150 grams.
The required daily intake of creatine is between 2 and 4 grams. The body takes about half of it needed from meat and fish of the daily food. 1 – 2% of the creatine is excreted per day as creatinine via the kidneys with the urine again.