Low ALT/SGPT means that there are normal levels of the liver enzyme alanine aminotransferase, or ALT, in the blood, which indicates that there is no disease or damage to the liver, according to WebMD. ALT used to be called SGPT, or serum glutamic pyruvic transaminase.
When the liver is damaged, it releases ALT into the bloodstream, which causes the level of ALT to increase. If ALT is elevated, it most likely indicates liver damage. There are small amounts of ALT in the kidneys, heart, muscles, and pancreas as well, so an elevated ALT could also indicate severe systemic damage to these organs and tissues.