Is my ALT too high?
Enter your result to see which clinical range it falls into.
Within the genuinely healthy range for men (ACG ~29–33 IU/L; Prati et al. proposed ~30).
Healthy ranges: Prati et al., Ann Intern Med 2002; ACG guideline (Kwo et al., 2017). Standard lab upper limits vary (~40–55 IU/L). Estimate for education only — not a diagnosis. Interpret lab results with your clinician.
ALT ranges, and what each one means
These are the same thresholds the interpreter above uses.
Male
| Range | Category | What it means |
|---|---|---|
| < 33 IU/L | Optimal | Within the genuinely healthy range for men (ACG ~29–33 IU/L; Prati et al. proposed ~30). |
| 33–55 IU/L | High-normal | Inside most labs' “normal” range, but above the ~30 IU/L healthy ceiling. Fatty liver can hide here — worth pairing with metabolic markers (HOMA-IR, triglycerides). |
| ≥ 55 IU/L | Elevated | Above the standard lab upper limit. Read the pattern (AST, GGT, the AST:ALT ratio) and the trend rather than one value, and evaluate with a clinician. |
Female
| Range | Category | What it means |
|---|---|---|
| < 25 IU/L | Optimal | Within the genuinely healthy range for women (ACG ~19–25 IU/L; Prati et al. proposed ~19). |
| 25–55 IU/L | High-normal | Inside most labs' “normal” range, but above the ~19–25 IU/L healthy ceiling. Fatty liver can hide here — worth pairing with metabolic markers (HOMA-IR, triglycerides). |
| ≥ 55 IU/L | Elevated | Above the standard lab upper limit. Read the pattern (AST, GGT, the AST:ALT ratio) and the trend rather than one value, and evaluate with a clinician. |
Where these come from: Healthy ranges: Prati et al., Ann Intern Med 2002; ACG guideline (Kwo et al., 2017). Standard lab upper limits vary (~40–55 IU/L).
Estimate for education only — not a diagnosis. Interpret lab results with your clinician.
The short version
- ALT and AST are enzymes released when liver cells are injured. ALT is fairly liver-specific; AST also comes from muscle, heart, and red blood cells, so an isolated AST rise isn't always about the liver.
- The 'normal' ALT range printed by most labs (often up to ~40–55) is too lenient. Research suggests a truly healthy upper limit is closer to ~30 for men and ~19–25 for women.
- A normal ALT does not rule out liver disease. People with fatty liver (MASLD) — including some with significant fibrosis — frequently have ALT values squarely inside the normal range.
- GGT is the underrated one. Beyond flagging alcohol and bile-duct issues, it tracks with metabolic syndrome and is independently associated with cardiovascular and overall mortality in large studies.
- The AST-to-ALT ratio adds context: a ratio under 1 is typical of fatty liver, while a ratio above 1 — especially approaching 2 — can point toward alcohol-related injury or advanced scarring.
- A single, mildly elevated enzyme is common and often benign. What matters is the pattern, the trend, the cause, and — for fatty liver — whether there's fibrosis, not the enzyme number alone.
The full guide
ALT, AST & GGT: What Your Liver Enzymes Actually Mean — and Why 'Normal' Can Mislead
9 min read · Sean Moshrefi, PharmD, MS
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