I wasn't going to tell this story. But the whole premise of this series is that John tests himself and tells the truth about what he finds. So here it is.
Last year, during the period when I was writing the first ten articles in this series, I ordered a Bloody Good Test for myself. Partly because it would be embarrassing to write about testing and not do it. Partly because I was curious. Most of my results were fine. Ferritin had improved since I started supplementing. Vitamin D was adequate. Thyroid, cholesterol, blood sugar, all within range.
My ALT was 52 U/L. The reference range upper limit is 40 for men.
Not dramatically high. Not clinically alarming. But flagged. And I knew exactly why.
The preceding three months had not been my finest. I'd been working long hours on the series launch. My gym attendance had dropped off. I was drinking more than usual. Not excessively by Australian standards, but more than I should, more consistently than I should. A few beers most nights. Takeaway more often than I'd like to admit. Sleep quality average at best.
My GP wasn't concerned. She said it was mildly elevated, almost certainly lifestyle-related, and to retest in three months after making some adjustments. I cut back on drinking, got back to the gym, ate better. Retested. ALT came back at 28. Normal.
It was a small thing. But it stuck with me, because the liver is one of those organs that doesn't complain until it's in serious trouble. An ALT of 52 felt like nothing. No symptoms. No pain. No indication whatsoever that anything was off. Without the blood test, I'd have had no idea. And if I'd kept going the way I was going for years instead of months, the story might have been different.
An estimated 5.5 million Australians are living with non-alcoholic fatty liver disease. That number is projected to reach 7 million by 2030. Most of them have no symptoms and no idea. This article is about what liver function tests actually measure, why they matter, and what it means when your enzymes are elevated, even mildly.
A note before we get into it
General information only. I'm not a doctor or a hepatologist. Liver function test interpretation depends on the pattern of results, clinical context, and often repeat testing. A single mildly elevated enzyme doesn't necessarily indicate disease.
If you have known liver disease, hepatitis, are a heavy drinker, or are taking medications that affect the liver, work with your GP or specialist.
What your liver actually does
Your liver is a processing plant. It transforms substances into forms your body can safely use or eliminate. It's one of the hardest-working organs you own, performing over 500 distinct functions.
The big ones: processing nutrients absorbed from your gut, metabolising medications and alcohol, producing bile for fat digestion, storing glycogen (your short-term energy reserve), producing proteins for blood clotting and immune function, filtering toxins and waste products from the blood, and regulating cholesterol and triglyceride metabolism.
The thing about the liver is its resilience and its silence. It can sustain significant damage before producing symptoms. By the time you feel something (pain, jaundice, fatigue, swelling) the injury is usually advanced. Blood tests matter here. Liver enzymes are often the first signal that something's not right, and they can flag problems years before symptoms appear.
The tests: what each enzyme tells you
A standard liver function test (LFT) panel includes several markers. Here's what each one measures and what an abnormal result might suggest.
ALT (Alanine Aminotransferase)
What it measures
ALT is an enzyme found predominantly in liver cells. When liver cells are damaged or inflamed, ALT leaks into the bloodstream.
Why it's the most liver-specific marker
ALT is more specific to the liver than most other enzymes in the panel. An elevated ALT strongly suggests liver cell injury, though it doesn't tell you why. The cause could be anything from fatty liver to viral hepatitis, medication toxicity, excessive alcohol, or autoimmune disease.
Reference range
Typically below 40 U/L for men and below 30 U/L for women, though some guidelines have proposed lower thresholds. In the AusDiab study, 13% of Australian adults had elevated ALT, including 22% of people with diabetes and 18% of those with obesity.
What my GP was thinking when she saw my 52
"Is this lifestyle-related, medication-related, or is there an underlying process? It's mild, so let's retest after intervention and see if it normalises."
AST (Aspartate Aminotransferase)
What it measures
AST is an enzyme found in the liver, but also in the heart, muscles, kidneys, and brain. It's less liver-specific than ALT.
Why it matters
AST is most useful alongside ALT. The ratio between the two can suggest different causes. An ALT predominance (ALT higher than AST) is typical of fatty liver disease. An AST predominance (AST higher than ALT) can suggest alcoholic liver disease or cirrhosis. Neither ratio is diagnostic on its own, but it helps guide the clinical investigation.
The exercise caveat
Because AST is present in muscle tissue, intense exercise can elevate AST without any liver involvement. If you did a heavy gym session the day before your blood test, your AST might be temporarily elevated. This is why preparation matters.
GGT (Gamma-Glutamyl Transferase)
What it measures
GGT is an enzyme involved in the metabolism of glutathione, one of the body's key antioxidants. It's found in the liver, bile ducts, kidneys, and pancreas.
Why it matters
GGT is one of the most sensitive markers of liver stress, particularly from alcohol. Even moderate regular alcohol consumption can elevate GGT. It's also elevated in bile duct problems, fatty liver, and with certain medications.
The honesty test
GGT is sometimes informally called the "alcohol test" because it responds so reliably to regular drinking. When my ALT was 52, my GP asked about my GGT too. It was mildly elevated. That combination (elevated ALT plus elevated GGT in a man who'd been drinking more than usual) painted a clear picture without needing further investigation at that point.
Test it with Bloody Good:
Product: GGT Blood Test
ALP (Alkaline Phosphatase)
What it measures
ALP is an enzyme found in the liver, bile ducts, bones, and intestines.
How clinicians use it
An isolated ALP elevation can indicate bile duct problems (obstruction, cholestasis) or bone conditions. In the liver context, it's most useful for distinguishing between liver cell damage (ALT/AST pattern) and bile duct obstruction (ALP/GGT pattern). Elevated ALP with elevated GGT is more likely bile duct-related. Elevated ALP with normal GGT may be bone-related.
Bilirubin
What it measures
Bilirubin is a yellow pigment produced when red blood cells are broken down. The liver processes bilirubin for excretion in bile.
Why it matters
Elevated bilirubin can indicate liver dysfunction, bile duct obstruction, or excessive red blood cell breakdown (haemolysis). Markedly elevated bilirubin produces jaundice, the yellowing of skin and eyes.
Mild elevations are common and often benign. Gilbert's syndrome, a harmless genetic variant affecting bilirubin processing, is present in roughly 5-10% of the population.
Albumin
What it measures
Albumin is a protein produced exclusively by the liver. It's the most abundant protein in your blood.
Why it's different from the enzymes
Albumin reflects your liver's synthetic function, its ability to make proteins. Low albumin can indicate chronic liver disease, malnutrition, kidney disease, or chronic inflammation. It's a marker of liver function rather than liver damage, which makes it clinically different from the enzymes above.
The condition nobody talks about: fatty liver disease
This is the section that prompted me to write this article.
Non-alcoholic fatty liver disease (NAFLD), recently renamed metabolic dysfunction-associated steatotic liver disease (MASLD), is the most common liver condition in Australia. An estimated 5.5 million Australians are affected. Prevalence has increased from roughly 33% to 39% over the past fifteen years in population studies, driven by rising rates of obesity and metabolic syndrome. Australia ranks third highest for NAFLD prevalence among comparable developed nations.
By 2030, projected NAFLD cases will reach 7 million. Advanced liver disease cases are expected to increase by up to 85%.
And most people with NAFLD have no idea they have it. Because it doesn't hurt. It doesn't produce symptoms until it's advanced. It doesn't show up on a routine physical examination. It shows up on blood tests, often as a mildly elevated ALT, sometimes with elevated GGT and triglycerides, and on imaging.
NAFLD exists on a spectrum. Simple steatosis (fat accumulation in the liver without significant inflammation) is the most common and mildest form. Non-alcoholic steatohepatitis (NASH) involves inflammation and liver cell damage alongside the fat. This is the stage where fibrosis can begin. If untreated, NASH can progress to cirrhosis and liver cancer.
The drivers are the same metabolic factors that run through this entire series: insulin resistance, obesity (particularly abdominal), type 2 diabetes, dyslipidaemia (high triglycerides, low HDL), and metabolic syndrome. It's a liver disease that's fundamentally metabolic. That's why the name change to MASLD makes clinical sense, even if nobody's used to it yet.
Here's the part that gets me. The conversation around liver disease in Australia still centres on alcohol and hepatitis. Those are important causes. But the single largest contributor to liver disease burden in this country is now metabolic, not viral, not alcoholic. And most of the public health conversation hasn't caught up.
Alcohol, medications, and other common causes of elevated enzymes
NAFLD is the most common cause, but it's not the only one. Other reasons your liver enzymes might be elevated:
Alcohol. Even moderate regular consumption can elevate GGT and ALT. Binge drinking can cause acute spikes. Chronic heavy drinking leads to alcoholic liver disease, which has its own progression from fatty liver to hepatitis to cirrhosis.
Medications. Common culprits include paracetamol (especially in excess or with alcohol), statins (though statin-related liver enzyme elevations are typically mild and not a reason to stop therapy without discussion), NSAIDs, some antibiotics, anticonvulsants, and certain supplements. That includes some herbal products marketed for "liver detox," which is ironic.
Viral hepatitis. Hepatitis B and C can cause chronic liver inflammation. Screening is recommended for anyone with risk factors, including people born in high-prevalence countries, people who've received blood products before 1990, and people with a history of injecting drug use.
Autoimmune liver disease. Less common, but worth considering if liver enzymes are persistently elevated without an obvious lifestyle or metabolic cause.
Coeliac disease. Unexplained liver enzyme elevation can be a presentation of coeliac disease. Another reason to consider coeliac antibody testing alongside an LFT if the cause isn't clear.
Intense exercise. As mentioned, AST (and to a lesser extent ALT) can be temporarily elevated after hard training. This is physiological, not pathological, but it can confuse the picture if you don't mention it to your clinician.
Who should be testing
Anyone with metabolic risk factors. Overweight or obesity (particularly abdominal), insulin resistance, pre-diabetes or type 2 diabetes, elevated triglycerides, metabolic syndrome. All of these increase the risk of NAFLD significantly. If you read the weight gain article and identified with the metabolic pattern, liver function should be part of your panel.
Anyone who drinks regularly. If you're consuming alcohol most days of the week, an LFT gives you objective feedback on how your liver is coping.
Anyone starting or taking medications that affect the liver. Statins, paracetamol (regular use), certain antibiotics, anticonvulsants. Your GP may recommend baseline and periodic LFTs.
Anyone who's never had a liver screen. If you're over 35 and have never had liver enzymes checked, it's a reasonable baseline given the prevalence of NAFLD in the general population.
Anyone with unexplained fatigue. Liver disease is on the differential for persistent tiredness, though it typically causes fatigue only when advanced.
How to prepare
Fast for 8-12 hours. While not strictly required for all LFT markers, fasting produces the most consistent results. If you're doing other tests alongside (lipids, glucose), you'll need to fast for those anyway.
Avoid alcohol for 48-72 hours before. This gives GGT and ALT time to return to a baseline level rather than reflecting acute intake.
Avoid heavy exercise for 24-48 hours. Intense training can elevate AST and, to a lesser extent, ALT.
Continue medications unless told otherwise. If your GP wants to see how your liver enzymes look on your current medication, test while taking it.
Mention all supplements and herbal products. Some "natural" supplements can stress the liver. Your clinician needs to know what you're taking.
Understanding your results
Liver function tests are interpreted as a pattern. Here's a general guide.
| Pattern | What it may suggest |
|---|---|
| Mild ALT elevation (40-80 U/L men, 30-60 U/L women) | Most common finding. Usually metabolic (NAFLD) or lifestyle-related (alcohol, diet). Warrants lifestyle review and repeat testing. Does not automatically indicate serious disease. |
| Moderate ALT elevation (80-200 U/L) | More significant. Requires investigation: viral hepatitis screening, autoimmune markers, medication review, and potentially imaging (ultrasound). |
| Significantly elevated ALT (above 200 U/L) | Urgent evaluation needed. May indicate acute hepatitis (viral, drug-induced, autoimmune), significant liver injury, or other serious pathology. |
| ALT > AST | Typical of NAFLD/MASLD. |
| AST > ALT | Suggests alcoholic liver disease or possible cirrhosis. |
| Elevated GGT with elevated ALT | Alcohol or metabolic liver disease likely. |
| Elevated ALP with elevated GGT | Suggests bile duct involvement. May need imaging. |
| Low albumin | Indicates impaired liver synthetic function. Concerning for chronic liver disease. |
| Elevated bilirubin with otherwise normal enzymes | Often Gilbert's syndrome (benign). If accompanied by other abnormalities, warrants investigation. |
Tests to consider through Bloody Good
The liver test
Liver Function Test (LFT) covers the full panel: ALT, AST, GGT, ALP, bilirubin, albumin, total protein.
Individual liver markers
If you want to track specific enzymes:
Metabolic context
These help interpret liver results in a broader picture:
Cholesterol (Lipid Studies inc. HDL) — triglycerides are a key marker of metabolic liver health
HbA1c — blood sugar regulation is central to NAFLD risk
Fasting Insulin — insulin resistance drives fatty liver development
Fasting Glucose — metabolic context
Rule-out tests
Iron Studies (Including Ferritin) — iron overload (haemochromatosis) can cause elevated liver enzymes and is particularly relevant in Australia
Full Blood Count (FBC) — baseline blood health
If you want broad coverage
The Bloody Good Test covers 100 biomarkers including the full LFT panel alongside cholesterol, HbA1c, iron studies, kidney function, thyroid, and more. This is how I found my own elevated ALT. Not because I was looking for a liver problem, but as part of a broad baseline.
What to do after an abnormal result
If enzymes are mildly elevated (likely lifestyle cause): Address the obvious factors. Reduce or eliminate alcohol. Improve dietary quality. Increase physical activity. Lose weight if relevant. Retest in 8-12 weeks. Most lifestyle-related enzyme elevations normalise with these changes. Mine did.
If enzymes remain elevated after lifestyle changes: Your GP will investigate further. That typically means viral hepatitis screening (hepatitis B and C), autoimmune markers, iron studies (haemochromatosis is an important Australian cause), coeliac antibodies, and likely a liver ultrasound.
If NAFLD is confirmed: Management is lifestyle-first. Weight loss of 7-10% of body weight can reverse steatosis and improve liver inflammation. No approved medication specifically for NAFLD exists yet (though several are in late-stage trials). The metabolic foundations (insulin resistance, blood sugar, lipids) are the treatment targets.
If results suggest significant liver disease: Referral to a hepatologist or gastroenterologist for further assessment, which may include elastography (FibroScan) to assess liver stiffness and fibrosis, or in some cases, liver biopsy.
Monitor over time. The liver is remarkably regenerative. It responds to change. But it also responds to continued insult. Regular monitoring (at least annually for anyone with metabolic risk factors, more frequently during active intervention) turns a single data point into a trajectory.
Explore more biomarkers
Browse the Bloody Good Biomarker Directory
General information only. This article is not medical advice and is not a substitute for care from a qualified health professional. If you have concerning symptoms or urgent health issues, seek medical attention promptly.