Short answer: "Liver function tests" (a liver panel, LFTs) is a group of blood tests: the enzymes ALT and AST, which leak into the blood when liver cells are irritated; ALP and GGT, linked mainly to the bile ducts (ALP also to bone); bilirubin, a breakdown product of red cells processed by the liver; and albumin, a protein the liver makes. Despite the name, most of them show liver irritation or bile flow rather than how well the liver works.
At a glance
| ALT and AST | Enzymes that leak from irritated liver cells |
|---|---|
| ALP and GGT | Linked to the bile ducts; ALP also to bone |
| Bilirubin | A breakdown product of red cells, processed by the liver |
| Albumin | A protein the liver makes |
| Units | U/L for enzymes; mg/dL or µmol/L for bilirubin; g/dL or g/L for albumin |
| Keep | All lines with the date and the medicines you were taking |
What the test measures
Each test points to a different part of the picture:
- ALT is found mainly in the liver; AST also in muscle and the heart. Their ratio sometimes helps doctors.
- ALP comes from the bile ducts and bone (it is naturally higher in growing children and in pregnancy). GGT rises with bile-duct problems and with alcohol and some medicines.
- Bilirubin rises when red cells break down faster or when the liver or bile ducts do not clear it; a mild harmless rise (Gilbert's syndrome) is common.
- Albumin reflects the liver's production over weeks, and also nutrition and kidney losses.
When it is ordered
Common reasons, which your doctor adapts to you:
- as part of a routine or comprehensive metabolic panel;
- when symptoms such as yellow skin, dark urine or abdominal pain need checking;
- to monitor medicines that can affect the liver, or known liver conditions.
How the result is written on the report
| Result on the report | LOINC code | Usual unit | Also seen as |
|---|---|---|---|
| ALT | 1742-6 | U/L | µkat/L (÷60) |
| AST | 1920-8 | U/L | µkat/L |
| GGT | 2324-2 | U/L | µkat/L |
| Alkaline phosphatase (ALP) | 6768-6 | U/L | µkat/L |
| Bilirubin, total | 1975-2 | mg/dL | µmol/L (×17.1) |
| Albumin | 1751-7 | g/dL | g/L (×10) |
Enzymes are usually in U/L (international units per litre); some Nordic labs use µkat/L (1 µkat/L ≈ 60 U/L). Bilirubin: µmol/L = mg/dL × 17.1. Albumin: g/L = g/dL × 10.
Reading your report
A slightly raised enzyme on one test is common and often temporary (recent exercise, a viral illness, some medicines, alcohol). Doctors look at which enzymes are raised, by how much, and whether it persists on a repeat test. Enzyme ranges vary more between labs than most tests, so keep the range of each report.
Keeping the results in your record
Scan or photograph the report in Anpheros Daily: each value is read with its unit and the laboratory's reference range, you check it, and it is stored with its LOINC code as an HL7 FHIR Observation, a format used by many hospitals and national health systems. Results from different laboratories line up on one chart over time, and the lab unit converter helps when two reports use different units. Our guide on how to read lab results explains reference ranges and flags in general; the lab results guide for a new doctor shows how to share them.
What this page does not do
It explains what the test is and how the result is written. It does not interpret your result, diagnose or recommend treatment: the meaning of a value depends on your history, your other results and how the sample was taken, and that is your doctor's job.
Related pages
Sources
Frequently asked questions
Do liver function tests measure how well the liver works?
Only partly. ALT, AST, ALP and GGT mostly show irritation or bile flow; albumin and clotting tests (INR) reflect the liver's production.
Can exercise raise liver enzymes?
Yes. Hard exercise can raise AST and sometimes ALT for a few days, because muscle contains them too.
What is the difference between ALT and AST?
ALT is found mainly in the liver; AST also in muscle and the heart, so AST is less specific to the liver.
How do I convert bilirubin from mg/dL to µmol/L?
Multiply by 17.1. For example, 1.0 mg/dL is about 17 µmol/L.
Try it in Anpheros Daily
Photograph your lab report and Anpheros Daily lines up each value with its reference range, so you can compare reports from different laboratories.
How it works in the app →
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