L-citrulline is a naturally occurring amino acid. It is found in some foods like watermelons and is also produced naturally by the body.

L-citrulline is used for Alzheimer’s disease, dementia, fatigue, muscle weakness, sickle cell disease, erectile dysfunction, high blood pressure, and diabetes. It is used for heart disease, body building, increasing energy, and for improving athletic performance.
 
How does it work?
L-citrulline is a naturally occurring amino acid found in food, such as watermelons, and also made in the body. Our bodies change L-citrulline into another amino acid called L-arginine and also to nitric oxide. L-citrulline might help increase the supply of ingredients the body needs to making certain proteins. It might also help open up veins and arteries to improve blood flow and reduce blood pressure.