Many people infected with hepatitis C don't know they have this often chronic, blood-borne, lifelong viral infection that affects about 4.1 million Americans, according to the National Institute for Diabetes and Digestive and Kidney Disorders. Hepatitis C infection accounts for around 50 percent of all cases of cirrhosis, liver cancer and end-stage liver disease, the NIDDK reports. The wide variation in symptoms and markers of this disease means that it's possible to have no active signs of it as well as normal liver enzyme levels, which are determined by blood tests that evaluate liver function.
Tests
Damage to cells in the liver or elsewhere releases enzymes into the bloodstream. Tests to evaluate liver function include several common blood tests for these enzymes, such as aspartate aminotransferase, also called AST or SGOT, and alanine aminotransferase, also called ALT or SGPT. Both enzymes are found in liver tissue, but AST is also present in heart, muscle, kidney and brain cells. An elevated ALT is specific for liver damage while AST is not. Your doctor may also order an alkaline phosphatase test, also called ALP, to evaluate liver function.
Normal Levels
Normal serum levels of ALT range from 7 to 56 units per liter, according to Hepatitis Central, while normal levels of AST range from 4 to 40 U/L. Normal ALT levels generally indicate only mild damage to the liver from hepatitis C. About 40 percent of people with chronic hepatitis C have repeatedly normal ALT levels, the NIDDK reports. Your doctor may do a blood test called HCV RNA to confirm that you do have hepatitis C in these cases. Alkaline phosphatase levels most often do not rise in hepatitis C unless you have cirrhosis, according to the NIDDK. Normal levels of ALP range from 30 to 120 U/L.
Significance
Normal liver enzyme levels in hepatitis C don't mean you don't have the disease, or that you won't ever have liver problems from hepatitis C. They mean only that liver damage is not occurring at this time. If you undergo antiviral treatment for the infection, your liver enzymes may drop back into a normal range. A rise in levels after treatment may indicate that the infection is becoming active again.
Changes
If you have hepatitis C, an increase in your liver enzymes may indicate that the infection has started to damage the liver cells. Normally, ALT levels are higher than AST, but if liver damage progresses to cirrhosis, AST levels may be higher. If you have an acute rather than chronic hepatitis C infection, liver enzymes may be much higher than normal, as high as thousands of units per liter.
