Reference ranges
ALT reference range
Reference ranges describe the interval a laboratory prints next to your result. They are not a diagnosis of what is “normal” for you personally — your clinician interprets results in context.
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What ALT measures
ALT is found in liver cells and elsewhere. Blood levels can change for many reasons; labs report activity or concentration according to their method.
Why ranges differ
Laboratories set their own reference intervals using their methods, equipment, and population data. That is why the range on your Quest report may differ from a LabCorp report — always use the interval printed on your source document.
Common units
ALT is often reported in U/L. Confirm units on your original report before comparing values across time.