In short
- Fatty liver (MASLD) is common in adults and has no symptoms for a long time. The first sign is often a mildly raised ALT or GGT at a routine check.
- FIB-4 is a calculation from age, AST, ALT and platelets that estimates the likelihood of advanced scarring. Below 1.3 the likelihood is low, above 2.67 high (EASL).
- FIB-4 is less reliable under the age of 35. After 65 a higher lower cut-off of 2.0 applies. Our app takes this into account by itself.
- A raised ALT is not always fat: viral hepatitis, iron, alcohol, medicines and even hard training raise the enzymes.
- Fatty liver is reversible. Losing 7–10 % of body weight reduces liver fat and, in some people, inflammation too.
Fatty liver is today the most common liver disease. It is also the most overlooked, because it does not hurt. This article explains what in the blood points to it and how its severity is assessed without a biopsy. It also shows what moves the numbers in three months.
What in the blood points to fatty liver
| Test | What it means | Pitfalls |
|---|---|---|
| ALT | An enzyme that leaks from liver cells under strain. In MASLD it is most often mildly raised. | Hard training and some medicines raise it; wait 48–72 hours after exercise. |
| AST | A related enzyme; the AST/ALT ratio helps separate the causes. | Also released from muscles — raised after exercise or injury. |
| GGT | Sensitive to alcohol and medicines. | 24 hours without alcohol before the blood draw, otherwise the value is misleading. |
| Platelets | Fall with advanced liver disease; they go into the FIB-4 calculation. | — |
| Metabolic markers (glucose, HbA1c, triglycerides) | MASLD is by definition linked to metabolic risk. | A 12-hour fast is needed for the assessment. |
| HBsAg, anti-HCV, ferritin with TSAT | Rule out viral hepatitis and iron overload. | Makes sense with any persistently raised ALT (BSG 2017). |
What FIB-4 is and how to read it
FIB-4 is a simple calculation from four values you already have: age, AST, ALT and platelets. It does not tell you whether you have fat in the liver. It estimates the likelihood of advanced scarring (fibrosis), which is what counts in the long run.
| FIB-4 | Meaning | What comes next |
|---|---|---|
| below 1.3 (after 65, below 2.0) | Advanced fibrosis unlikely. | Lifestyle care, repeat in 1–3 years. |
| 1.3–2.67 | Grey zone. | Further assessment: elastography or the ELF test with a specialist. |
| above 2.67 | Raised likelihood of advanced fibrosis. | Referral to a specialist. |
Under the age of 35 FIB-4 is less reliable (often falsely reassuring). Our app calculates it automatically and applies the age cut-offs. You see the result with an explanation, not as a bare number.
How FIB-4 is calculated
The formula is simple and you can check it yourself:
FIB-4 = (age in years × AST) ÷ (platelets × √ALT)
AST and ALT in U/L, platelets in 109/L (so 220, not 220,000).
Example. A person aged 52, AST 38 U/L, ALT 55 U/L, platelets 210 × 109/L. The numerator is 52 × 38 = 1976. The denominator is 210 × √55 = 210 × 7.42 = 1558. FIB-4 is therefore 1976 ÷ 1558 = 1.27. That is just under the 1.3 cut-off, so advanced fibrosis is unlikely.
Notice how strongly age affects the result. The same laboratory picture in a 70-year-old would give a FIB-4 of about 1.71. That is exactly why after 65 a higher lower cut-off of 2.0 applies — otherwise there would be too many false positives.
Where FIB-4 gets it wrong
FIB-4 is a screening tool, not a diagnosis. It is fair to know when it must not be read literally:
- It does not measure fat, but scarring. You can have a markedly fatty liver and a FIB-4 below 1.3. A low result is not confirmation that the liver is healthy.
- Low platelets from another cause (bone marrow diseases, some medicines, infections) falsely raise the result, because they are in the denominator.
- Under 35 it is often falsely reassuring, over 65 falsely alarming — hence the separate age cut-offs.
- After hard exercise AST is raised from the muscles, not from the liver. Rest for 48–72 hours before the blood draw, or the calculation is not meaningful.
- It does not separate the cause. Alcohol-related and metabolic damage give the same result. Your history, GGT and the AST/ALT ratio explain the difference, not the calculation.
Who should be checked
European guidelines (EASL–EASD–EASO 2024) do not recommend general screening. They recommend case-finding in those at risk: type 2 diabetes, overweight or obesity, metabolic syndrome, persistently raised ALT and regular alcohol use. If you belong to any of these groups, a FIB-4 calculation makes sense. Upload your report to Blood Lab 360 and it is calculated and explained for you.
What helps in three months
- Losing 7–10 % of body weight. The best-proven measure: it reduces liver fat and, in some people, inflammation and scarring too.
- Fewer sugary drinks and less fructose. Liquid sugar goes straight into liver fat.
- Exercise, even without weight loss. Endurance or strength training, 150 minutes a week, reduces liver fat.
- Alcohol. With a fatty liver every extra gram is a burden. With a raised GGT, stopping is the fastest measure.
- Controlled blood sugar and lipids. MASLD is a metabolic disease — HbA1c and triglycerides are part of the same picture.
Re-test after three months. Before that the enzymes and triglycerides have not settled enough for a fair comparison.
Honestly: no supplement is a proven cure for fatty liver. What works is weight loss, exercise and less alcohol — boring, but true.
Frequently asked questions
Does a raised ALT mean liver disease?
Not necessarily. The most common causes are fat in the liver, alcohol, medicines and recent hard training. What matters is whether the rise is persistent — that is why the test is repeated.
How is FIB-4 calculated?
From age, AST, ALT and platelets. If all four values are on your report, our app does the calculation and explains it together with the age cut-offs.
Does a low FIB-4 mean my liver is healthy?
No. FIB-4 estimates scarring, not fat. You can have a fatty liver and at the same time a FIB-4 below 1.3. Assessing fat needs an imaging test.
Do I need an ultrasound?
Ultrasound is useful for assessing liver fat, elastography for assessing scarring. Blood tests help decide when an imaging test is needed.
May I drink alcohol before the blood draw?
No. At least 24 hours without alcohol, otherwise GGT will be raised because of the drink and not because of the liver.
Is fatty liver reversible?
In the early stage, yes. Losing 7–10 % of body weight is the best-proven measure; in some people inflammation and scarring also decrease.
Sources: EASL–EASD–EASO 2024 — guideline on steatotic liver disease (MASLD), case-finding in those at risk, FIB-4 as the first step · EASL 2021 — non-invasive tests, FIB-4 age cut-offs · BSG 2017 (Newsome et al., Gut 2018) — management of abnormal liver tests · IFCC C-RIDL — reference intervals for liver enzymes · WHO/EASL 2022 — haemochromatosis and TSAT.
