ALT is an enzyme that leaks out of liver cells when they are irritated or injured. In most adults a raised value means fat in the liver, and that fat tends to travel with insulin resistance, the same process that shows up in blood sugar and triglycerides. Laboratories print upper limits from about 40 to 65. The gastroenterology guideline puts a healthy normal near 29 to 33 in men and 19 to 25 in women.
Two neighbors help me read it. GGT is a second liver enzyme that rises with alcohol, body fat and insulin resistance, and it reports a change in drinking within about a month. Uric acid causes gout when it runs high. Outside gout it is best read as a marker of insulin resistance, alcohol, weight and kidney function, because trials of lowering it did not protect the kidneys.
hs-CRP is made by the liver in response to inflammation anywhere in the body. Across 54 long studies, the risk of heart disease and stroke rose steadily with it. But genetic studies show that CRP is the messenger, not the cause, so I read it as a gauge. I like to see hs-CRP under 1.0, measured when a person is well. That is my target, not a universal cutoff. A single reading above 10 usually reflects a recent illness and should be repeated once you are well.
Each of these can mislead:
- A normal ALT does not rule out fat in the liver.
- ALT lives in muscle too, so a hard week of training can raise it.
- Hormone pills taken by mouth can raise hs-CRP with no inflammation at all.
- A raised ALT that stays raised has other causes, including alcohol, medicines, supplements and viral hepatitis, and sorting those is a doctor's job.
One marker is a clue. Three are a story. Read together, these tell you where to look. They do not tell you what you have.