L-carnitine has certain functions in some physiological processes of maintaining infant life and promoting infant development. Adults can synthesize and maintain the concentration of L-carnitine required for normal metabolism by themselves, but infants' synthesis ability of L-carnitine is weak, only 12-15% of adults, especially premature infants, which can not meet their normal metabolic needs. Infants grow and develop rapidly, and the required carnitine increases sharply.