On almost every blood result with liver values are two names that look alike: ALT and AST. They are enzymes that sit in your cells and leak into your blood when cells get damaged. That is why a doctor uses them to gauge whether something is going on with your liver.
The nice thing is that the two together tell you more than each on its own. Not only whether there is damage, but sometimes also which direction to look for the cause.
What do ALT and AST measure?
ALT (also ALAT) sits mainly in your liver cells. That makes it a fairly specific liver value: if ALT rises, that usually points toward the liver. AST (also ASAT) sits in your liver too, but also in your muscles and your heart. That makes AST less specific.
That difference explains why a doctor looks at both. A high AST without a high ALT can, for instance, also come from your muscles instead of your liver.
| Enzyme | Where it mainly sits | What a rise can mean |
|---|---|---|
| ALT (ALAT) | Mainly liver cells | Fairly specific to the liver; sensitive to cell damage |
| AST (ASAT) | Liver, muscle and heart | Less specific; can also come from muscle or exertion |
You will also find these values as individual markers: ALT and AST. A third liver value, GGT, we cover separately.
Why does the AST/ALT ratio matter?
Doctors look not only at the separate numbers, but also at the ratio between AST and ALT. That ratio can give a hint about the possible cause. With some patterns a doctor thinks sooner of alcohol, with others sooner of fatty liver or something else.
Important: such a ratio is a hint, not a diagnosis. A doctor uses it to choose a direction, not to draw a conclusion. The role of alcohol is in our piece on alcohol and your liver values.
Why can exercise raise my AST?
This is a point that surprises many sporty men. Because AST sits in your muscles too, a heavy training or an intense workout can temporarily raise your AST, without anything being wrong with your liver. The same goes for a muscle injury.
If you want a clean picture of your liver, it is smart to avoid heavy training just before a blood test. If you do train, tell your doctor, so that a raised AST is read in the right context.
What if my ALT or AST is too high?
A slightly raised value without symptoms is often no reason for panic, but it is a reason to check the cause and repeat the value. According to Thuisarts.nl, an abnormal liver value is a reason to look at causes such as alcohol, overweight or medicines, and not to assume the worst straight away.
A markedly raised value, or a combination of abnormal liver values, calls for further checks with a doctor. So always discuss an abnormal result, because a single measurement is a snapshot.
What a blood test shows you
A liver test measures ALT, AST and often GGT at once, so your doctor can read them together. The Liver Function panel maps these values. The broader story is in our pillar on liver values in men.
Frequently asked questions
What is the difference between ALAT and ALT?
Nothing, they are two names for the same enzyme. ALAT is the Dutch abbreviation, ALT the international one. The same goes for ASAT and AST. On your result you can come across both spellings, depending on the laboratory.
Can my AST be high from exercise?
Yes. Because AST sits in muscle tissue too, a heavy training can temporarily raise the value without your liver being involved. That is why it is smart not to do an intense workout before a liver test, or to mention it to your doctor.
How often should I have my liver values checked?
If you have no symptoms and no risk factors, routine testing is usually not needed. If you do have risk factors such as overweight or regular alcohol, a doctor decides whether and how often monitoring makes sense. One measurement is a snapshot, the trend over time often says more.
Sources
- Thuisarts.nl. I have an abnormal liver value.
- Maag Lever Darm Stichting. Liver values in blood.
- NHG (Dutch College of General Practitioners). Blood testing for liver values.
Disclaimer
Caliberhealth works with BIG-registered doctors who review your blood results. This article provides general information and is not a substitute for medical advice from a GP or specialist. A blood test is a tool, not a diagnosis in itself. For serious or persistent symptoms, contact your GP, or call 112 in an emergency.
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