Elevated liver enzymes mean ALT or AST, enzymes released when liver cells are injured, are above your laboratory's range. Common causes are fatty liver disease (now called MASLD), alcohol, medicines and viral hepatitis. Heavy weight training can raise both for days. A raised result is a reason to find the cause, not a diagnosis.
It is also not something to repeat and forget. This guide covers what ALT and AST measure, the MASLD name change, common causes, the FIB-4 scarring score and the symptoms that need urgent care.
What do ALT and AST measure?
ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes in liver cells that are released into the blood when those cells are injured, according to the British Society of Gastroenterology (BSG) guideline. Raised ALT or AST is the most common abnormality on liver blood tests.
ALT is the more liver-specific of the two. AST is abundant in skeletal, heart and smooth muscle, so it can rise with muscle injury or a heart attack. Results are reported in units per liter, shown as U/L or IU/L.
Your laboratory's upper limit may sit above what liver specialists regard as healthy. AASLD guidance puts a true normal ALT at 29 to 33 U/L in men and notes that most laboratory ranges are higher. It says ALT or AST above 30 U/L, fluctuating or lasting 6 to 12 months, may suggest chronic liver injury.
What is MASLD?
MASLD stands for metabolic dysfunction-associated steatotic liver disease, the 2023 replacement name for non-alcoholic fatty liver disease (NAFLD). Steatotic means fatty. A multisociety Delphi consensus of 236 panelists from 56 countries chose the name and defined MASLD as liver fat plus at least one of five cardiometabolic risk factors.
The same statement created MetALD for people with MASLD who also drink more: 210 to 420 g of alcohol a week for men. Our standard drinks vs alcohol units guide converts grams into the drinks used in your country.
NICE renamed its guideline to MASLD in July 2026, while Australia's primary care consensus still uses MAFLD (metabolic dysfunction-associated fatty liver disease).
| Topic | US | UK | Australia |
|---|---|---|---|
| Name in current guidance | MASLD (2023 nomenclature co-led by AASLD) | MASLD (NICE, renamed July 2026) | MAFLD (GESA primary care consensus) |
| First check for scarring | FIB-4; 1.3 or above leads to elastography or ELF (AASLD) | ELF test for people with MASLD (NICE); FIB-4 first (BSG) | FIB-4; 1.3 to 2.7 leads to second-line tests (GESA) |
| Low-risk FIB-4 cut-off over 65 | 2.0 (AASLD) | 2.0 (BSG) | 2.0 (GESA) |
Fatty liver is common. Australia's healthdirect says it affects about 1 in 3 Australian adults, with overweight around the abdomen, type 2 diabetes or insulin resistance, and high cholesterol or triglycerides among the most common causes. Our guides to insulin resistance vs prediabetes and visceral fat cover those links.
Normal enzymes do not rule fatty liver out. NICE notes that more than 80% of people with MASLD have normal routine liver blood tests, and advises against using those tests to rule MASLD out.
What causes elevated liver enzymes?
The BSG lists the common causes of a raised ALT and AST pattern as viral hepatitis, fatty liver disease, alcohol-related liver disease, autoimmune hepatitis and drug-induced liver injury.
Alcohol deserves an honest count. The BSG notes that the relative risk of cirrhosis is about 3 at 20 UK units a week and about 30 at 80 units a week, and that obesity roughly doubles the risk of liver disease at any given intake once body mass index passes 35.
Medicines and supplements matter too. The BSG asks clinicians to take a drug history covering prescribed, over-the-counter, herbal and recreational products, and to revisit it when other tests find no cause.
Iron can also be involved. The BSG includes ferritin and transferrin saturation in its standard liver screen, but notes that an isolated high ferritin is common in fatty liver and alcohol excess and does not by itself mean hemochromatosis; see high ferritin in men.
Can exercise raise liver enzymes?
Yes. In a 2008 study, 15 healthy men used to moderate exercise, but not weightlifting, did a one-hour weightlifting session. AST and ALT rose significantly and stayed raised for at least 7 days, while creatine kinase, a muscle enzyme, rose sharply. GGT, alkaline phosphatase and bilirubin stayed within the normal range.
The authors concluded that intensive muscular exercise should be considered as a cause of raised liver tests in people without symptoms. If you trained hard in the week before a blood test, tell whoever ordered it, and ask whether a repeat after a rest period makes sense.
Lifters on creatine have a separate kidney test issue; see creatine and creatinine.
How is FIB-4 used to check for liver scarring?
FIB-4 is a score calculated from your age, AST, ALT and platelet count that estimates the chance of advanced liver scarring (fibrosis). The BSG gives the formula as age multiplied by AST, divided by the platelet count multiplied by the square root of ALT. It uses age in years, AST and ALT in U/L and platelets in 10⁹/L, so units matter; ask your clinician or laboratory to calculate and interpret it.
In the US, AASLD guidance treats a FIB-4 below 1.3 as low risk, to be reassessed periodically. A score of 1.3 or above should lead to a second test, preferably elastography (a scan that measures liver stiffness) or the enhanced liver fibrosis (ELF) blood test, and above 2.67 direct referral should be considered. A cut-off of 2.0 is used over 65, and the score has low accuracy under 35. FIB-4 should not be used during acute illness, and recent muscle injury, including from unusually hard exercise, can raise AST and falsely raise the score. Mention either before the result is interpreted.
In Australia, the GESA consensus summary in the Medical Journal of Australia uses the same lower cut-off. A score below 1.3 has a negative predictive value above 95% for advanced fibrosis and should be repeated at least every three years; 1.3 to 2.7 calls for elastography or a fibrosis blood test, and above 2.7 calls for referral.
In the UK, the BSG uses FIB-4 first, while NICE recommends the ELF test for people diagnosed with MASLD. NICE diagnoses advanced fibrosis at an ELF score of 10.51 or above, refers those people to a liver specialist, and reassesses adults below that score every 3 years. NICE also advises against using routine liver blood tests to assess advanced fibrosis, and both the BSG and the GESA summary note that standard liver tests can be normal even with cirrhosis.
Should you repeat a high liver enzyme test?
Only when there is a clear short-term explanation, such as hard training or a recent illness. The BSG notes that in one UK primary care study, 84% of abnormal liver tests were still abnormal a month later and 75% at two years. It therefore recommends looking for the cause rather than repeating the same panel, unless a transient cause is strongly suspected.
AASLD guidance adds that aminotransferases persistently above normal for more than 6 months are a reason to consider specialist referral.
Practical checks after a high ALT or AST
1. Look at the pattern, not one number.
The BSG describes predominantly raised ALT and AST as a hepatitic pattern, and raised alkaline phosphatase and GGT as a cholestatic one, pointing to bile flow. Ask which pattern your result shows.
2. List everything you take.
Include prescriptions, over-the-counter painkillers, herbal products, supplements and anything used for training, ideally with photos of the labels.
3. Count your drinks honestly.
Write down a typical week. The number matters more than the label you would give your drinking.
4. Note training in the week before the test.
Record the date and type of any heavy session, so the result is read in context.
5. Ask whether a FIB-4 has been calculated.
The GESA summary recommends assessment for adults with obesity, type 2 diabetes or two or more metabolic risk factors. If that describes you, ask for the score, because enzymes alone cannot rule out scarring.
When should you see a doctor about elevated liver enzymes?
Book a review for any unexplained raised result: with a primary care physician in the US, or a GP in the UK or Australia. Ask what pattern the result shows, whether you need hepatitis B and C tests, whether a FIB-4 score has been calculated, and what would trigger a referral.
Some symptoms need prompt attention. healthdirect lists yellow skin or eyes (jaundice), bruising, dark urine, a swollen belly, vomiting blood, black stools and itchy skin as signs of more serious liver disease. Vomiting blood always needs urgent medical assessment. The NHS says to call 999 or go to an emergency department if you are vomiting blood and also feel faint, dizzy or confused, or have black stools; in the US call 911 and in Australia 000. If the bleeding has stopped and you feel otherwise well, still get urgent medical advice the same day.
Frequently asked questions
What causes elevated liver enzymes?
Common causes are fatty liver disease (MASLD), alcohol, medicines and supplements, viral hepatitis, autoimmune hepatitis and inherited conditions such as hemochromatosis. Heavy exercise can also raise AST and ALT for several days. Your doctor uses the pattern of results, your history and follow-up tests to narrow down the cause.
Can exercise raise liver enzymes?
Yes. In a study of 15 healthy men, an hour of weightlifting raised AST and ALT significantly for at least 7 days, alongside a sharp rise in creatine kinase, a muscle enzyme. Tell the person ordering your test about hard training in the week before, especially heavy lifting.
What is MASLD?
MASLD, or metabolic dysfunction-associated steatotic liver disease, is the 2023 name for what used to be called non-alcoholic fatty liver disease. It means fat in the liver plus at least one cardiometabolic risk factor. NICE adopted the name in July 2026, while Australian primary care guidance uses the similar term MAFLD.
Can you have fatty liver with normal liver enzymes?
Yes. NICE notes that more than 80% of people with MASLD have normal routine liver blood tests, and advises against using those tests to rule it out. UK and Australian guidance also note that ALT and AST can be normal even with cirrhosis, which is why scores such as FIB-4 are used.
Should I worry about mildly elevated liver enzymes?
A mildly raised ALT or AST is the commonest abnormality on liver blood tests, but it deserves an explanation rather than a repeat and a shrug. In one UK study, 84% of abnormal tests were still abnormal a month later. Ask about alcohol, medicines, hepatitis tests and a FIB-4 score.
The short version
Elevated liver enzymes are a signal to find the cause, most often fatty liver, alcohol, medicines or viral hepatitis, with hard training as a temporary explanation to rule out. Normal enzymes do not exclude fatty liver or scarring, which is why FIB-4 and related tests exist. Bring an honest drink count and a full list of what you take. Jaundice or vomiting blood needs prompt medical attention.
This article is general education, not medical advice. It does not replace your own physician.
