Insight into your liver enzymes.
ALT and AST are enzymes found mainly in the liver cells. When they are released into the blood, that gives insight into irritation or damage to liver cells.
Also known as: ALT, AST, ALAT, ASAT, transaminases, liver values
Personal assessment by our BIG-registered Bloodworks® doctors
By the Bloodworks editorial team
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Background
What are ALT and AST?
ALT and AST are enzymes the body uses in the metabolism of amino acids. They are located mainly inside the cells. If liver cells become irritated or damaged, these enzymes leak into the blood and the measured value rises. That is why they are commonly called the liver values or the transaminases. ALT is also known as ALAT, and AST as ASAT.
There is an important difference between the two. ALT is fairly specific to the liver. AST also occurs in muscle tissue, in the heart and in red blood cells. A heavy training session can therefore raise the AST value without anything being wrong with the liver. By measuring both enzymes together, the doctor can better judge whether a rise fits the liver or another source. Common causes of raised liver enzymes are alcohol, excess weight with fatty liver, certain medicines and viral infections.
In brief
Liver cells
ALT and AST are released on irritation or cell damage
ALT is more specific
ALT points more clearly to the liver than AST
AST is also in muscle
Heavy training can raise AST without a liver problem
Lifestyle counts
Alcohol, weight and medication influence the values
This marker is also included in
Testing several values in a single draw takes one blood collection and gives a more complete picture. The choice is yours.
Common reasons to test
When can insight into your Liver enzymes be valuable?
Below are some situations in which measuring Liver enzymes can provide insight.
Insight into your liver values
ALT and AST are the usual first step in assessing irritation or damage to liver cells.
With regular alcohol use
Alcohol places a burden on the liver. Those who want to know what their use does to the liver values have these enzymes measured.
With excess weight or fatty liver
Fat accumulation in the liver is a common cause of raised liver enzymes. A test gives insight into this.
With long-term medication use
Some medicines are broken down in the liver or can place a burden on it. Insight into the liver values is then relevant.
For athletes
AST also comes from muscle tissue. Athletes therefore sometimes see a rise after a heavy training session while the liver is working normally.
Tracking a value over time
For liver values the development over time is often more informative than a single measurement. Re-testing makes a change visible.
What your result means
AST or ALT too high or too low: what does your liver value mean?
ALT and AST are measured in units per litre (U/L). The laboratory states the reference values that apply there alongside your result. Important: alcohol, weight, medication use and a heavy training session shortly before the draw can influence these values.
A low value
A low ALT or AST value generally has no medical significance and does not point to a liver problem. Our doctor provides explanation and context with your result.
A normal value
Values within the laboratory's reference values give a reassuring picture of the liver cells at this moment. It remains a snapshot. Liver enzymes can be normal while something is still going on in the liver, which is why the doctor also considers your symptoms and context.
An elevated value
Raised liver enzymes may point to irritation or damage of liver cells. Common explanations are alcohol, fatty liver with excess weight, certain medicines and viral infections. With an isolated raised AST, the source may also lie in the muscles, for example after intensive training. A single measurement is not a diagnosis. Our doctor explains what your values mean and whether re-testing or follow-up via your GP is customary.
How we interpret your result
Our doctors interpret your ALT and AST against the laboratory's reference values and your personal context, such as lifestyle, alcohol use, training load, medication use and any known conditions.
Related tests
Often combined with Liver enzymes.
A single marker gives one perspective. For a broader picture you can combine Liver enzymes with a theme package or related markers.
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Frequently asked questions
Everything you want to know
Do I need to fast for a liver enzyme test?
No, you do not need to fast for ALT and AST. If you are also measuring glucose or cholesterol at the same time, fasting is customary.
What is the difference between ALT and AST?
ALT is fairly specific to the liver cells. AST also occurs in muscle tissue, in the heart and in red blood cells. A rise in ALT therefore points more clearly to the liver, while a raised AST may also have another source.
Can exercise influence my liver values?
Yes. A heavy training session, especially strength training, can raise the AST value because the enzyme also comes from muscle tissue. For a well comparable measurement it is customary to avoid very intensive training the day before the draw.
How long should I avoid alcohol before the test?
There is no fixed rule. Alcohol can influence the liver values. If you want to know what your usual situation shows, test without changing your habits and mention your alcohol use, so the doctor can take it into account.
Which medicines influence the liver values?
Various medicines are broken down in the liver and can raise the values, for example some painkillers, cholesterol-lowering drugs, antibiotics and anti-epileptics. Supplements and herbal preparations can also play a role. Please mention your medication with your result.
Does an elevated value mean my liver is damaged?
Not necessarily. A single measurement is not a diagnosis. A temporary rise occurs after an infection, after alcohol use or after a heavy training session. The doctor looks at the level, at the ratio between the enzymes and at your context, and advises whether re-testing is useful.
How often should I have my liver values measured?
A single measurement is enough for initial insight. With a previously abnormal value, with long-term medication use, or with a lifestyle change you want to follow, re-testing after a few months is customary.
What do I do with my result?
You receive a PDF report with your values and personal explanation. What you do with it, such as discussing it with your GP, remains entirely your choice.
What do ALT and AST stand for?
ALT stands for alanine aminotransferase and AST for aspartate aminotransferase. In Dutch reports the same enzymes are called ALAT and ASAT. Together they are often referred to as the transaminases, or simply the liver values.
What is a normal AST value?
What counts as normal is determined by the laboratory. Reference values differ per laboratory and per measurement method, and depend on factors such as sex. The values that apply to your result are always stated with your report. Our doctor assesses your AST together with your ALT and your personal situation.
What does it mean if both AST and ALT are raised?
If both enzymes are raised, that may point to irritation or damage of liver cells. Common explanations are alcohol, fatty liver with excess weight, certain medicines and viral infections. If only AST is raised and ALT is not, the source may also lie outside the liver, for example in muscle tissue after intensive training. A single measurement is not a diagnosis. Our doctor looks at the ratio between the two enzymes, at the level and at your context, and explains whether re-testing or follow-up via your GP is customary.
In the Health Guide
Read more about this value
Where do you give blood?
You can give blood at collection points across the Netherlands, usually without an appointment.
Find a collection point near you or read how a blood draw works.
Ready for insight into your liver enzymes?
You receive your ALT and AST including personal explanation from a doctor, typically within 2 working days. No referral required.
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