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Liver

ALT and fatty liver: what the liver enzyme says with excess weight

ALT (alanine aminotransferase) works as an enzyme in the liver cells, according to the NVKC a protein that helps convert one substance into another. According to Thuisarts, with a fatty liver the liver stores too much fat in those liver cells.

According to Thuisarts, a fatty liver is one of the possible reasons why the liver tests in the blood are abnormal, and according to the NVKC ALT ends up in the blood when liver cells are damaged. A blood test is the only way to know the ALT value.

Diagnostiek voor U gives an ALT below 45 U/L for men and below 34 U/L for women as the reference values.

Doctor's Assessment Included

ALT is an enzyme, a protein that helps cells convert one substance into another; it is found mainly in the liver and enters the blood when liver cells are damaged. The four laboratories use an adult upper limit of 45 U/l for men and 34 U/l for women.

  • According to the NVKC, a slightly raised ALT without symptoms is not given a meaning straight away; only when the value is more than twice the upper limit is a search for the cause advised.
  • A normal or slightly raised ALT does not rule out serious liver disease such as cirrhosis, which is why ALT is often combined with other liver tests.
  • According to Thuisarts, when ALT is only slightly high, there is no clear cause and the person is not really ill, the GP can wait a few weeks and then test the blood again.

Reference Ranges

See the value that applies to you:

Choose male or female — this range differs by sex.

Enter your age — this range changes with age.

This range also depends on context such as cycle phase or sample material; the highlighted rows apply to your group.

Your reference range
u/l
8 71 u/l
Reference ranges by group, in u/l
Male · 1–5 years 9–35 u/l
9 35
Male · 6–12 years 10–35 u/l
10 35
Male · 13–18 years 9–42 u/l
9 42
Male · 19–50 years 13–71 u/l
13 71
Male · 51–65 years 13–64 u/l
13 64
Male · 66–80 years 11–54 u/l
11 54
Male · 81 years and older 9–42 u/l
9 42
Female · 1–5 years 10–33 u/l
10 33
Female · 6–12 years 9–33 u/l
9 33
Female · 13–18 years 8–35 u/l
8 35
Female · 19–50 years 9–44 u/l
9 44
Female · 51–65 years 11–52 u/l
11 52
Female · 66–80 years 10–46 u/l
10 46
Female · 81 years and older 8–37 u/l
8 37
8 71 u/l

Source: NVKC Reference population: Dutch general-practice population (NUMBER, n = 7,574,327)

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

ALT (Alanine Aminotransferase): what Dutch laboratories use

Reference ranges by group, in u/l
Star-shl · Male 0–45 U/l
0 45
Star-shl · Female 0–34 U/l
0 34
Unilabs · Male · 19 years and older 0–45 U/l
0 45
Unilabs · Female · 19 years and older 0–34 U/l
0 34
Certe · Male · 18 years and older · a limit, not a range < 45 U/L
45
Certe · Female · 18 years and older · a limit, not a range < 34 U/L
34
Diagnostiek voor U · Male · a limit, not a range < 45 U/L
45
Diagnostiek voor U · Female · a limit, not a range < 34 U/L
34
0 49.5 u/l

Source: Star-shl

Source: Unilabs

Source: Certe

Source: Diagnostiek voor U

Each value as the laboratory itself publishes it, retrieved in 2026.

ALT (Alanine Aminotransferase): what this test measures

In U/l, the ALT test shows how much ALT enzyme activity there is in the blood. According to Thuisarts, an ultrasound of the abdomen can show why the liver tests are abnormal, for example a fatty liver, but an ultrasound does not always find a cause.

ALT (Alanine Aminotransferase): why this value matters

According to Malakouti and colleagues, non-alcoholic fatty liver disease is the most common cause of mildly abnormal liver enzymes such as ALT in the United States. According to the BSG, a fatty liver that leads to chronic liver disease often goes together with only a mild or moderate abnormality of the liver tests.

ALT (Alanine Aminotransferase): how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Which test
GLP-1 Check-in Panel · €109,- · GLP-1 Extended Panel · €196,- · GLP-1 Baseline Panel · €214,-
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

ALT (Alanine Aminotransferase): how to prepare

  1. Better no hard training beforehand

    Recommended

    Hard exercise in the 48 hours before can raise this value temporarily. Plan the draw on a rest day if you can.

  • Water is always fine. Drink as usual beforehand, it makes the draw easier.
  • Take your usual medication, unless your own doctor told you otherwise.

ALT (Alanine Aminotransferase): when is testing worthwhile?

According to the NVKC, an ALT test is sometimes done with mild complaints such as tiredness, to look for a longer-standing liver disease. According to the NVKC, ALT is also measured to check whether the treatment of a liver disease is working.

ALT (Alanine Aminotransferase): symptoms of a high or low value

Low Levels

A low ALT falls within the reference values at Diagnostiek voor U, because Diagnostiek voor U gives only an upper limit for ALT. Researchers publishing in European Urology Open Science in 2023 describe a low ALT in the general population as going together with muscle loss.

High Levels

According to Thuisarts, a fatty liver is one of the possible reasons for a raised ALT, and it can come from drinking a lot of alcohol, diabetes or being overweight. According to Thuisarts, a fatty liver usually causes no symptoms, but in some people the liver becomes inflamed after a while.

ALT (Alanine Aminotransferase): causes of a low or high value

What lowers the value

  • Low muscle mass

    In studies of the general population, a low ALT goes together with loss of muscle mass.

  • Vitamin B6 deficiency

    Vitamin B6 is needed to make ALT; a deficiency, which is common with long-term heavy drinking, reduces how much ALT is made.

What raises the value

  • Fatty liver

    A fatty liver, too much fat in the liver, can raise ALT and the other liver tests in the blood.

  • Alcohol

    Drinking alcohol is one of the causes of a raised ALT and other raised liver tests.

  • Medicines and drugs

    Medicines that can damage the liver, including ones bought without a prescription, and drugs such as cocaine or ecstasy can raise ALT and the other liver tests.

  • Acute viral hepatitis

    An ALT more than 15 times the upper limit is almost always caused by acute hepatitis, which is usually caused by a virus.

  • Heavy weight training

    In one study, ALT stayed raised for at least 7 days after an hour of heavy weight training in healthy men who were not used to it.

ALT (Alanine Aminotransferase): lifestyle and this value

With a raised ALT, your GP is the person to see. For people who are overweight, Thuisarts advises trying to lose weight by eating healthily and moving more, because according to Thuisarts that reduces the fat in the liver.

ALT (Alanine Aminotransferase): frequently asked questions

Can diabetes raise ALT?

According to Thuisarts, diabetes can lead to a fatty liver, and a fatty liver is one of the possible reasons why liver tests such as ALT are abnormal.

Is a fatty liver the only cause of a high ALT with excess weight?

No, according to Thuisarts a raised ALT can also come from medicines that can damage the liver, alcohol, a viral liver inflammation, gallstones or drugs, and sometimes the cause does not become clear.

ALT (Alanine Aminotransferase): sources

  1. den Elzen WPJ, Brouwer N, Thelen MH, Le Cessie S, Haagen I-A, Cobbaert CM. NUMBER: standardized reference intervals in the Netherlands using a 'big data' approach. Clin Chem Lab Med 2018;57(1):42-56. (retrieved 2026) doi.org
  2. Star-shl, Labbepalingen (referentiewaarden per bepaling), star-shl.nl, geraadpleegd 2026-10-01 (retrieved 2026) star-shl.nl
  3. Unilabs, Bepalingenklapper (referentiewaarden per bepaling), bepalingenklapper.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenklapper.nl
  4. Certe, Bepalingenwijzer (referentiewaarden per bepaling), bepalingenwijzer.certe.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenwijzer.certe.nl
  5. Diagnostiek voor U, eLabgids (Referentiewaarden DvU), diagnostiek.getincontrol.eu, geraadpleegd 2026-10-01 (retrieved 2026) diagnostiek.getincontrol.eu
  6. Laufer M, et al. Low Alanine Aminotransferase, as a Marker of Sarcopenia and Frailty, Is Associated with Shorter Survival Among Prostate Cancer Patients and Survivors. Eur Urol Open Sci 2023. (retrieved 2026) pmc.ncbi.nlm.nih.gov
  7. Malakouti M, et al. Elevated Liver Enzymes in Asymptomatic Patients - What Should I Do? J Clin Transl Hepatol 2017;5(4):394-403. (retrieved 2026) pmc.ncbi.nlm.nih.gov
  8. NHG, Thuisarts.nl: De levertesten van mijn bloed zijn niet goed, geraadpleegd 2026-10-06 (retrieved 2026) thuisarts.nl
  9. NVKC, Alles over testen: ALAT, allesovertesten.nl, geraadpleegd 2026-10-06 (retrieved 2026) allesovertesten.nl
  10. Pettersson J, et al. Muscular exercise can cause highly pathological liver function tests in healthy men. Br J Clin Pharmacol 2008;65(2):253-259. (retrieved 2026) pmc.ncbi.nlm.nih.gov

Test Products

This marker is included in the following test panels.

GLP-1

GLP-1 Check-in Panel

The 3-month safety and progress check clinics do: pancreas, liver, kidneys, salts and your metabolic progress on GLP-1 medication.

ALT (Alanine Aminotransferase) AST (Aspartate Aminotransferase) HDL Cholesterol HbA1c (Glycated Hemoglobin) Potassium Sodium Glucose (Fasting) Total Cholesterol Lipase Creatinine Triglycerides eGFR (Estimated Glomerular Filtration Rate) LDL Cholesterol Cholesterol/HDL Ratio Non-HDL Cholesterol LDL/HDL Ratio
€109,-
GLP-1

GLP-1 Extended Panel

The 6-month measurement: everything from the check-in plus insulin, ApoB and your nutrients — especially relevant if you have been eating much less for a while.

Insulin (Fasting) ALT (Alanine Aminotransferase) AST (Aspartate Aminotransferase) HDL Cholesterol HbA1c (Glycated Hemoglobin) ApoB (Apolipoprotein B) Vitamin B12 Ferritin Potassium Sodium Glucose (Fasting) Total Cholesterol Albumin Lipase Creatinine Vitamin D (25-OH) Triglycerides HOMA-IR eGFR (Estimated Glomerular Filtration Rate) LDL Cholesterol Cholesterol/HDL Ratio Non-HDL Cholesterol LDL/HDL Ratio
€196,-
GLP-1

GLP-1 Baseline Panel

Your starting point before the first injection: blood sugar, cholesterol, pancreas, liver, kidneys, thyroid and nutrients in one measurement.

Insulin (Fasting) ALT (Alanine Aminotransferase) TSH (Thyroid Stimulating Hormone) AST (Aspartate Aminotransferase) HDL Cholesterol HbA1c (Glycated Hemoglobin) Bilirubin (Total) ApoB (Apolipoprotein B) Vitamin B12 Ferritin Potassium Sodium Glucose (Fasting) Total Cholesterol Albumin Lipase Creatinine Vitamin D (25-OH) Triglycerides Bilirubin (Direct) Bilirubin (Indirect) HOMA-IR eGFR (Estimated Glomerular Filtration Rate) LDL Cholesterol Cholesterol/HDL Ratio Non-HDL Cholesterol LDL/HDL Ratio
€214,-

Medical reviewer

Medical standards

Dr. Naimi oversees the medical standards behind our content and assessments.

Medical policy
CIBG Ministerie van Volksgezondheid,
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ALT (Alanine Aminotransferase)

€8,-