Citrulline is a non-essential amino acid that is an important intermediate in the urea cycle, functioning along with other amino acids to rid the body of ammonia, a by-product of protein metabolism. Citrulline also plays an important role in the healing process and in the maintenance of a healthy immune system. This extra strength product has more L-Citrulline (1,200 mg per tablet) than our regular strength product (750 mg per capsule). Natural color variation may occur in this product.