Aspartate Aminotransferase

Yes. Unlike ALT, which is fairly liver-specific, AST (aspartate aminotransferase) is also present in skeletal muscle, heart, and red blood cells. That's why hard workouts, and even intramuscular injections, can release AST into the blood and raise the value without any liver problem. An elevated AST is only part of the picture until you know where it's coming from.

A typical normal AST range is about 10 to 40 U/L, with some variation between labs. Because AST comes from muscle and other tissues as well as the liver, mild elevations are common in physically active people. Your physician interprets it together with ALT and GGT rather than in isolation.

Look at AST alongside ALT and GGT. If AST is up but ALT and GGT are normal, the source is more likely muscle — from lifting, an intramuscular injection, or muscle breakdown — rather than the liver. A creatine kinase (CK) test can confirm a muscle source, since CK rises sharply after intense exercise. When ALT and GGT are also elevated, that shifts suspicion toward the liver and warrants a physician's evaluation.

Yes, transiently. An intramuscular testosterone injection causes minor local muscle trauma, and hard training around the same time adds to it, so AST (and CK) can rise for a few days without indicating any liver issue. It typically resolves on its own. To avoid a misleading result, separate your blood draw from recent injections and intense workouts, and have your doctor check ALT and GGT to rule out a true liver cause.