ALT and GGT Levels by Age: Liver Enzymes in Australian Adults

ALT and GGT levels by age and sex

In Vively members, ALT changed little with age. The median was 17 to 20 U/L in women in every age group and 29 to 30 U/L in men until their 60s, when it fell to 24 U/L. The gap between the sexes was the clearest pattern: 20% to 24% of men aged 18 to 59 had an ALT above 40 U/L, against 3% to 8% of women.

GGT rose with age, more so in women. Median GGT in women went from 13 U/L at 18 to 29 to 18 U/L at 60 and over, and the share above 50 U/L rose from 1% to 2% under 40 to 6% at 60 and over. In men the median was 19 to 22 U/L, and 8% to 10% of men aged 30 and over had a GGT above 50 U/L.

Against the tighter Vively optimal range for ALT (10 to 20 U/L for women, 10 to 30 U/L for men), 34% to 48% of women and 29% to 48% of men sat outside it, mostly above.

Normal ALT and GGT ranges in Australia

Each lab sets its own reference range, so read your result against the range printed on your report. The ranges used in the Vively app are:

The Vively optimal range for ALT is lower than most lab limits. The American College of Gastroenterology's 2017 guideline puts the true healthy upper limit of ALT at 29 to 33 U/L for men and 19 to 25 U/L for women, because lab ranges were built from groups that included people with undiagnosed fatty liver. The optimal range is what we aim for to support long-term health. It is not a diagnostic cut-off.

In every age group, 6% to 12% of Vively women and 12% to 20% of men had an ALT above the range on their own lab report.

What ALT and GGT measure

ALT (alanine aminotransferase) is an enzyme found mainly in liver cells. When liver cells are stressed or damaged, ALT leaks into the blood, so a raised ALT is the most specific sign on a standard panel that the liver itself is under strain.

GGT (gamma-glutamyl transferase) sits in the liver and bile ducts. It rises with alcohol, some medicines, fatty liver and blocked bile flow. GGT on its own doesn't say which, which is why it is read with ALT, AST, ALP and bilirubin. Large studies have also linked higher GGT within the normal range to heart disease. In 163,944 Austrian adults followed for 17 years, higher GGT went with higher cardiovascular death rates.

What raises ALT and GGT

• Fat in the liver. Metabolic dysfunction-associated steatotic liver disease (MASLD, previously called non-alcoholic fatty liver disease) is the most common cause of a mildly raised ALT. An Australian modelling study estimated 5.5 million Australians had it in 2019. It goes with extra weight around the middle, insulin resistance and high triglycerides.
• Alcohol. Regular drinking raises GGT first. ALT and AST can rise too, with AST often higher than ALT.
• Medicines and supplements. Paracetamol at high doses, statins, some antibiotics, anti-epileptic medicines and some herbal products can raise liver enzymes. Anti-epileptic medicines raise GGT in particular.
• Hard exercise. Weight training and long runs can raise ALT and AST for several days, because muscle also contains these enzymes. In one Swedish study, ALT stayed raised for up to a week after a weights session in men not used to it.
• Infection. Hepatitis B and C, and some other viral infections, raise ALT. Hepatitis B is more common in people born in Asia, the Pacific and Africa.
• Less common causes. Iron overload (haemochromatosis), coeliac disease, thyroid problems, autoimmune hepatitis and blocked bile ducts.

Do you need to fast? Not for ALT or GGT alone. The Baseline Health Check is a fasting test because of glucose, insulin and triglycerides, so fast overnight. Skip alcohol and hard exercise for two to three days before the test so they don't confuse the result.

Is an ALT of 40 or 70 high?

An ALT of 40 U/L is at or just above the upper limit for women on most Australian lab reports, and about at the limit for men. An ALT of 70 U/L is about double the upper limit. On its own, that is a mild rise. The Gastroenterological Society of Australia (GESA) describes mild rises as under 5 times the upper limit, and these are most often from fatty liver, alcohol or medicines.

One raised result is a reason to look for the cause and repeat the test, not a diagnosis. A GP will usually ask about alcohol, medicines and supplements, check for hepatitis B and C, look at your weight, blood sugar and triglycerides, and repeat the liver tests. An ultrasound may follow if the rise persists.

What does a GGT of 50 mean?

A GGT of 50 U/L is above the range used in the Vively app for women (5 to 35 U/L) and at the top of the range for men (5 to 50 U/L). The usual causes are alcohol, fatty liver and medicines. A high GGT with a normal ALT often points to alcohol or a medicine. A high GGT with a high ALP points to the bile ducts and needs a GP to look at it.

How ALT and GGT fit with your other results

How to support healthy liver enzymes

Most mildly raised liver enzymes come down when the cause is dealt with.

• Cut back on alcohol. Australian guidelines recommend no more than 10 standard drinks a week and no more than 4 on any one day. GGT often falls within weeks of drinking less.
• Work on weight around the middle. In fatty liver, losing 7% to 10% of body weight reduces liver fat and ALT. Even 5% helps.
• Eat fewer refined carbohydrates and sugary drinks. Fructose in particular is turned into fat in the liver.
• Move most days. Exercise lowers liver fat even without weight loss.
• Review your medicines and supplements with your GP or pharmacist, including herbal products.

Retest about three months after a change, without hard exercise or alcohol in the days before, so you're comparing like with like.

When to see your GP

See your GP if your ALT or GGT is above the range on your report on two tests, or if your ALT is more than about 3 times the upper limit. See a doctor promptly if a raised result comes with yellow skin or eyes, dark urine, pale stools, itching, pain under the right ribs or unexplained weight loss.

Testing ALT and GGT with Vively

ALT and GGT are in the Baseline Health Check, with AST, ALP, bilirubin, albumin, triglycerides, fasting glucose, insulin and HOMA-IR. You don't need a referral from your own GP: a doctor in our network reviews and signs your request. You have one blood draw at one of our 3,700+ partner collection centres, and your results arrive in the Vively app, usually within a few days. A Vively practitioner reads your liver enzymes with your metabolic markers, and members have a targeted re-test after 3 months. Get your Baseline Health Check.