ALT: what it means

Also known as: alanine aminotransferase, SGPT

ALT is a liver enzyme; elevated levels are one of the most common signs of liver inflammation or injury.

What it measures

ALT (alanine aminotransferase) is an enzyme concentrated in liver cells. When those cells are inflamed or damaged, ALT leaks into the blood — making it a sensitive, though nonspecific, marker of liver stress. It's usually read with AST and the rest of a liver panel.

Typical range

Often roughly 7–55 U/L, with the upper limit varying by lab and, some argue, by sex and body weight.

Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.

What a high result can mean

Fatty liver disease (MASLD/NAFLD) — a very common cause of mild elevations
Alcohol, certain medications, or supplements
Viral hepatitis
Sometimes strenuous exercise

A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.

Why the trend matters

Mild ALT elevations are common and often fluctuate; the trend across draws separates a one-off bump from a persistent pattern that warrants a closer look.

When to talk to your doctor

Persistently elevated ALT — especially with AST — is worth discussing with your doctor, who may look at causes like fatty liver, medications, or alcohol.

Frequently asked questions

What does a high ALT mean?

ALT is a liver enzyme, so an elevation usually reflects liver inflammation or injury — very commonly from fatty liver disease, and also from alcohol, medications, or hepatitis.

How can I lower my ALT?

When the cause is fatty liver, weight loss, exercise, and reducing alcohol often lower ALT over time. Persistent elevations should be evaluated by a doctor to pin down the cause.

Is a slightly high ALT serious?

Mild ALT elevations are common and often fluctuate; the trend and the underlying cause matter more than a single mildly high value.

This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.