Arginine is a conditionally essential amino acid in humans and rodents. as it may be required depending on the health status or lifecycle of the individual. For example, while healthy adults can supply their own requirement for arginine, immature and rapidly growing individuals require arginine in their diet

and it is also essential under physiological stress, for example during recovery from burns, injury, and sepsis, or when the small intestine and kidneys, which are the major sites of arginine biosynthesis, have been damaged It is, however, an essential amino acid for birds, as they do not have a urea cycle.