Quick answer: for ALT levels, MedlinePlus gives a normal range of 4 to 36 U/L (0.07 to 0.60 microkat/L), and Cleveland Clinic cites a common range of 7 to 56 U/L. The 2017 American College of Gastroenterology (ACG) guideline sets a stricter "true healthy normal" of 29 to 33 U/L for men and 19 to 25 U/L for women, and says levels above that should be assessed. So an ALT of 40 U/L can be "normal" on one lab report and worth a follow-up by ACG standards.
ALT levels: normal range
| Source | ALT | Notes |
|---|---|---|
| ACG guideline 2017, men | 29 to 33 U/L (upper limit) | True healthy normal; above this should be assessed |
| ACG guideline 2017, women | 19 to 25 U/L (upper limit) | True healthy normal; above this should be assessed |
| MedlinePlus | 4 to 36 U/L | 0.07 to 0.60 microkat/L |
| Cleveland Clinic | 7 to 56 U/L | One common lab range; higher in males |
U/L and IU/L are used interchangeably for ALT. Cleveland Clinic also notes that about 1 in 20 healthy people will fall outside any lab's range.
MedlinePlus, Cleveland Clinic and the 2017 ACG guideline. The ACG bands are upper limits: values above them should be assessed.
What is ALT?
Alanine aminotransferase (ALT) is an enzyme found mainly in liver cells. When liver cells are damaged, ALT leaks into the blood. It is usually measured with AST, ALP and bilirubin, often as part of a comprehensive metabolic panel. Cleveland Clinic calls ALT more directly tied to liver health than AST, because AST is also found in the heart, muscles and pancreas. The ACG notes that an elevated ALT is associated with higher liver-related mortality. For bile duct problems, GGT adds more detail.
What high ALT means
A high ALT means liver cells are under strain. MedlinePlus and Cleveland Clinic list these causes:
- Fatty liver disease
- Alcohol-related liver injury
- Viral hepatitis (A, B or C) and autoimmune hepatitis
- Medicines and supplements, including acetaminophen toxicity
- Hemochromatosis (iron overload; see ferritin), cirrhosis and, less often, liver tumors
- Pancreatitis and mononucleosis
- Intense or extreme exercise, which can raise ALT temporarily
The ACG's workup for a raised ALT includes tests for viral hepatitis, an assessment for fatty liver and alcohol, screening for hemochromatosis, autoimmune hepatitis, Wilson's disease and alpha-1 antitrypsin deficiency, and a review of prescribed and over-the-counter medicines. A mildly raised ALT is common, but it should not be ignored.
How to read your ALT result
- Compare it with two lines: your lab's upper limit and the ACG healthy limit (33 U/L for men, 25 U/L for women).
- Think about the last 48 hours: a hard workout, alcohol or a new medicine or supplement can push it up.
- Repeat a mildly raised result before assuming anything.
- Look at the rest of the panel: AST, ALP, GGT and ferritin help point to the cause.
Worked example: ALT of 41 in a woman
Say a 46-year-old woman who drinks two glasses of wine most nights and has gained weight around the middle gets an ALT of 41 U/L, with AST of 30 U/L. Her lab uses a 7 to 56 U/L range, so the report shows no flag. Against the MedlinePlus range it is 5 over the 36 U/L limit, and against the ACG healthy limit for women (25 U/L) it is 16 over.
What might explain it: fatty liver and alcohol-related injury are the first two causes on the MedlinePlus and Cleveland Clinic list, and both fit her history. A hard workout in the previous two days or a new supplement could also push it up.
Questions to take to her doctor:
- Should we repeat the ALT in a few weeks, after cutting back on alcohol and avoiding hard exercise before the draw?
- If it stays high, should we follow the ACG workup: viral hepatitis tests, an assessment for fatty liver and screening for iron overload with ferritin?
- Should I add GGT or a full liver function test, and could any of my medicines or supplements be the cause?
What low ALT means
A low ALT is uncommon and usually not a concern. Cleveland Clinic notes it can occasionally reflect vitamin B6 deficiency or chronic kidney disease.
What lowers ALT
- Weight: if fatty liver is the cause, losing excess weight is the usual first step to discuss with your doctor; it tends to go with better triglycerides and A1C.
- Alcohol: cutting back or stopping removes a direct cause of liver injury.
- Medicines and supplements: review everything you take with your doctor or pharmacist, including over-the-counter pain relievers and herbal products. Do not stop prescribed medicines on your own.
- Timing: avoid very hard workouts in the day or two before a test, since intense exercise can raise ALT temporarily.
How to test ALT
MedlinePlus says no special preparation is needed for ALT alone; Cleveland Clinic says to fast 10 to 12 hours if ALT is part of a comprehensive metabolic panel, and to tell your provider about medicines and supplements. Repeat a mildly high result before drawing conclusions, and compare it with the ACG limits as well as your lab's range.
Which at-home tests include ALT
ALT is on four SiPhox panels: Heart & Metabolic, Thyroid Focus, Ultimate 360 and GLP Optimization. Longevity Essentials and Hormone Focus do not include it.
| SiPhox panel | Biomarkers per test | Per test, with shipping | Listed as |
|---|---|---|---|
| Heart & Metabolic | 28 | $149 | ALT (Liver) |
| Thyroid Focus | 21 | $149 | ALT (Liver) |
| Ultimate 360 | 62 | $274 | ALT (Liver) |
| GLP Optimization | 46 | $224 | ALT (Liver) |
Every one of these also reports AST and the AST:ALT ratio. Heart & Metabolic, GLP Optimization and Ultimate 360 add ALP and bilirubin, and GLP Optimization and Ultimate 360 add GGT. Collection is from the upper arm at home with no needle, and SiPhox does not include a doctor review, so share a raised ALT with your doctor. See the GLP-1 blood test page and our SiPhox review.
Heart & Metabolic
Lipids plus kidney and liver function: the panel for cardiovascular and metabolic risk.
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GLP Optimization
Built for people on GLP-1 medication: metabolic, liver, kidney, nutrient and iron markers.
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Ultimate 360
Everything on the four core panels plus iron studies, B12 and folate, GGT and PSA.
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Frequently asked questions
What is a normal ALT level?
Lab ranges run from about 4 to 36 U/L (MedlinePlus) to 7 to 56 U/L (Cleveland Clinic). The ACG says a truly healthy ALT is up to 29 to 33 U/L for men and 19 to 25 U/L for women.
Is an ALT of 40 high?
It is inside some lab ranges but above the ACG healthy limit for both men and women, so it is worth repeating and discussing with your doctor.
What causes high ALT?
Common causes include fatty liver disease, alcohol, medicines and supplements (including too much acetaminophen) and viral hepatitis (MedlinePlus; Cleveland Clinic).
Can exercise raise ALT?
Yes. Cleveland Clinic says intense or extreme exercise can cause a temporary rise, so avoid hard workouts right before a test.
Do I need to fast for an ALT test?
Not for ALT alone (MedlinePlus). If it is part of a comprehensive metabolic panel, Cleveland Clinic says to fast 10 to 12 hours.