ALT, also printed as SGPT, is an enzyme concentrated in liver cells. The test measures how much enzyme activity is present in the blood. It is ordered as part of a liver panel or a general checkup, often alongside AST. Your report's printed range decides how the value is read.
Because ALT is reported as enzyme activity rather than as an amount of a substance, the number depends on the assay and the way the laboratory expresses it. That is one reason two reports can look different even when little about the person has changed.
What the test measures
ALT stands for alanine aminotransferase. It is an enzyme that transfers an amino group from alanine to another molecule, and it sits in the highest concentration inside liver cells. Smaller amounts are present in the kidney and in muscle. When liver cells are injured or inflamed, the enzyme can pass into the blood, and the measured activity rises.
The test reports enzyme activity in the sample. It does not measure how much liver tissue there is, and it does not measure how well the liver is working. The panel is often called a liver function test, but ALT itself reflects liver cell injury more than liver function. Albumin and bilirubin give a different view, which is why the panel prints them together.
Why it may be ordered
- As part of a liver function panel or a broader health checkup.
- Alongside other liver tests when a clinician is assessing the liver.
- To follow a known liver condition over time, where the trend matters more than one value.
- When a medicine that can affect the liver is being monitored, at intervals the clinician chooses.
- When other findings or symptoms have prompted a clinician to look at the liver.
ALT is usually read with AST, ALP, GGT, bilirubin, and albumin, because the combination carries more information than any single enzyme. It is not a screening test, and one result does not confirm or rule out a liver condition.
The unit on your report
| What you may see | What it means |
|---|---|
| ALT, SGPT, GPT, alanine aminotransferase | The test name. SGPT is the older name for the same enzyme, and many reports still print both. |
| U/L | Units of enzyme activity per litre of serum. The most common unit on reports. |
| ukat/L | The SI unit for enzyme activity, used by some laboratories and countries. The same measurement on a different scale. |
| Serum ALT, S. ALT | The sample type. ALT is usually measured in serum or plasma. |
| Method, analyser, or reagent lot | Some reports name the method. It matters, because ranges are tied to the method that produced them. |
Why this page does not print a range
A reference range belongs to the laboratory, the method, the population it was built from, and the context it is meant for. Two labs can measure the same sample with different assays and print different ranges, and one lab can change its range when it changes method. Age and sex also matter: many labs print separate ranges for children and for men and women, and pregnancy can shift several liver tests.
So the range printed on the report that produced your value is the one that applies. Doctano keeps that printed range with the result and does not replace it with a general range from elsewhere. A value compared with a range from a different laboratory is not a meaningful comparison.
What a high value can mean
A higher ALT means more enzyme activity is present in the blood than the report's range allows for. That is most often a signal that liver cells are turning over or are under stress, but it is a non-specific signal: the same rise can come from several different situations.
Possible contributors include viral liver inflammation, alcohol-related liver injury, fat stored in the liver, some medicines, some herbal products, strenuous exercise, and muscle injury. A single raised value can be temporary, and it can also persist. Repeat testing and a clinical assessment are what tell those apart.
Some people with a raised ALT have no symptoms and no other changed liver test. Others have changes in bilirubin, ALP, or GGT that give the enzyme more context. A high ALT does not confirm or rule out any particular condition.
What a low value can mean
A value below the report's range is less often the focus of a liver panel, and it is not automatically meaningful. ALT activity depends on a cofactor derived from a B vitamin, so a low value can appear when that vitamin is in short supply. Low muscle mass and some long-term illnesses have also been associated with lower ALT activity.
None of that says anything certain about an individual result. A low ALT is read with the rest of the panel, the person's history, and the report's own range.
What can move the value
- Strenuous exercise. Heavy or unaccustomed exercise can raise ALT and AST for a time.
- Alcohol. Alcohol intake can raise liver enzymes, and the effect on a single result depends on recent intake.
- Body weight and metabolic factors. Higher body weight is associated with higher ALT activity.
- Medicines. Some pain relievers, antibiotics, anti-seizure medicines, and other drug classes can affect the liver and the enzyme result.
- Herbal and botanical products. Some have been associated with liver enzyme changes, and the product label does not always say so.
- Pregnancy. Pregnancy can change several liver tests, and some laboratories print separate ranges.
- Sample handling. A haemolysed sample can interfere with some assays.
- Method and calibration. Two labs can produce different values from the same sample.
What to compare it with
ALT is read with AST. The two enzymes sit in different proportions in different tissues, so clinicians often look at them together rather than as isolated numbers. ALP and GGT add information about the bile ducts, bilirubin reflects the liver's handling of a pigment, and albumin reflects how much protein the liver is making. A blood count and a muscle enzyme such as CK can help when a non-liver source is a possibility.
The most useful comparison, though, is the same test from the same laboratory over time. A value that drifts within the printed range across several reports is a different signal from one that moves sharply between two.
How to see the trend
Doctano reads the ALT value, its unit, and the reference range printed on the report. It keeps that range with the result, normalizes the test name across labs, and places the value on the profile's timeline. Each point opens the report it came from, so the original page can be checked.
ALT is sometimes printed in U/L and sometimes in ukat/L. Doctano normalizes units for the timeline, but verify the value and the unit against the original report before treating a change as real, especially when the two results came from different laboratories.
What this page is not
This page explains the test in general. It does not interpret your result, diagnose a condition, or recommend treatment. It is not medical advice. Verify the value and the unit against the original report, and discuss the result with a qualified professional.