L-Isoleucine is an essential amino acid that is routinely used by bodybuilders and athletes to improve performance and lengthen exercise regimens by increasing energy and endurance. L-Isoleucine is considered essential because the body cannot produce it on its own. It must be supplemented to get its benefits. Right after exercise, levels of Isoleucine are spent and require recovery. However, some choose to supplement Isoleucine prior to exercise to balance out the loss. This leads to faster muscle recovery. Isoleucine is generally thought of in conjunction with other Branch Chain Amino Acids including Valine and Leucine. When taking Isoleucine supplements, it is important to supplement other Branch Chain Amino Acids, or this can have an adverse effect on the kidneys and liver. For this reason, every one part of Isoleucine should always be taken with two parts Leucine and one part Valine. Isoleucine is unique from the others in that it alone is able to alter and keep blood sugar at normal levels while also helping to provide the muscles with energy. It is needed in order for the formation of hemoglobin to take place as well. While Isoleucine helps to keep levels of nitrogen regular in adults, it is essential in children to promote regular growth.