What it measures
Alanine aminotransferase (ALT) is an enzyme found mainly inside liver cells. When liver cells are inflamed or damaged, ALT leaks into the blood, so it is the most liver-specific enzyme in a standard liver function test.
Why people test it
- Part of a routine liver function test, as the main sign of liver cell inflammation or damage.
- Checked when fatty liver, hepatitis or alcohol-related liver disease is suspected.
- Monitored in people on medicines that can affect the liver, such as statins.
- Rises for several days after heavy weight training, as muscle also releases ALT, which can look like a liver problem.
- Oral anabolic steroids can raise ALT, so people who use them often have it checked.
Typical range
Ranges vary between labs with the method used, age and sex, and your report shows the lab's own range. One NHS trust's lab uses up to 40 U/L for adults; other labs set different upper limits for men and women. Source: Leeds Teaching Hospitals NHS Trust: Blood Sciences Reference Range Database v3.20.
Finger-prick or vein?
A finger-prick sample is usually fine for ALT.