ALT and AST blood tests: understanding your results

ALT is found mainly in the liver, while AST also occurs in muscle and other tissues. A change in either enzyme can signal cell irritation or injury, yet it does not by itself show the cause or how well the liver is functioning.

Your clinician compares each result with the laboratory reference interval and looks at the pattern between them. Other liver-panel results, such as bilirubin, alkaline phosphatase and albumin, can clarify whether the pattern concerns liver cells, bile flow or liver function.

Exercise-related muscle strain may affect AST, and medicines, supplements, alcohol use, infections and metabolic liver changes can influence one or both enzymes. A single abnormal reading therefore cannot establish a diagnosis.

Review the complete report rather than comparing isolated values online. Tell the clinician about prescribed medicines, non-prescription pain relievers, herbal products, gym supplements, recent strenuous activity, alcohol intake and any recent illness.

Depending on the pattern and your symptoms, the next step may be a repeat blood sample, additional blood tests or liver imaging. Do not stop a prescribed medicine solely because an enzyme result is outside range; the prescriber can weigh the medicine's benefit against the possible cause of the change.

Arrange prompt medical review if an abnormal result accompanies yellow skin or eyes, dark urine, pale stools, persistent vomiting, worsening pain in the upper right abdomen, marked swelling or unusual drowsiness.

Seek emergency help for confusion, collapse, severe weakness, vomiting blood or black stools. These symptoms drive the urgency regardless of whether ALT or AST is only mildly changed on the report.

Ask which value is outside this laboratory's interval, whether the wider liver panel shows a matching pattern, and whether recent exercise or a medicine could explain it. You can also ask when testing should be repeated and which symptoms should prompt earlier contact.