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  • Writer's pictureKim Atherton

Liver Function Tests Explained

Updated: Dec 12, 2023

Our Liver Function Tests are big indicators of health we can look at. The biggest misconception is that they reveal what is happening now in your body. Unfortunately that's not the case. By the time our Liver Function Tests show signs of being abnormal, we have already incurred liver injury or disease! You can see by the graphic below that we have normal amounts of circulating liver enzymes in our blood, but when our liver cells are damaged (busted open or lysed), the cells leak more and more of these liver enzymes - especially AST and ALT. So increased liver function enzymes = liver disease or damage that has already happened. The good news is that early intervention, as always, can turn things around - with the possible exception if your GGT is elevated. This is why it is wise to review results in terms of the optimal functional range. Keep an early eye on your ALT as discussed below.

Causes of Liver Issues:

Elevated Liver Function Tests Results can be explained by the following conditions:

  1. Alcoholic Liver Disease (ALD)

  2. Non-Alcoholic Fatty Liver Disease (NAFLD) with increased adiposity from poor dietary choices

  3. Viral infections affecting the liver

  4. Medications (Statins, anti-hypertensives, pain relief, anti-psychotics, antimicrobials, certain Herbal medicines, excess Vitamin A)

  5. Environmental toxins like heavy metals and chemicals

A graphic showing where the liver is in the body and the increased leakage of liver enzymes when the liver is damaged or diseased.
Healthy liver and diseased liver and their levels of liver enzymes released.

Liver Function Test Markers Explained

What are the liver function test markers referred to for explanation?

Liver Function Marker

​Description of Marker

Total Bilirubin

​Bilirubin is formed from the breakdown of Haemoglobin from RBC's as unconjugated bilirubin.

AST (Aspartate Aminotransferase)

An intracellular enzyme present inside every cells mitochondria - where energy is produced, like muscles. Can be increased in liver disease, heart attacks and muscle injury. It is a LATE marker to rise.

ALT (Alanine Aminotransferase)

The alarm raiser! An intracellular enzyme that will rise quickly in viral infections, like Hepatitis. It shows EARLY liver assault with leakage from ALT from inside liver cells. Herbs and medicines may also raise it. The higher the level, the more acute the situation.

De Ritis Ratio (AST:ALT Ratio). Used ONLY if AST and ALT values are out of healthy range.

It reflects the time course, or aggressiveness of liver disease.

ALP (Alkaline Phosphatase)

​An extracellular enzyme in the Kupfer cells outside the liver, that line the biliary duct where bile synthesis occurs. Being extracellular, the increase is as a defence mechanism.

GGT (Gamma-Glutamyl Transferase)

GGT can help decide the cause of an increased ALP - see below. GGT on its own, is a very sensitive marker that highlights oxidative stress with issues in Glutathione production (GGT maintains healthy Glutathione levels).

LDH (Lactate Dehydrogenase)

​Not a specific marker for liver disease.

Total Protein

Is the sum total of all proteins present in our blood. This includes the 2 major plasma proteins, albumin and globulin. Typically normal in liver disease. Protein should be in our blood and not seen in our urine.


Main transport protein produced by the liver. Typically normal in liver disease, but can also be low. Low albumin is a sign of chronic disease.


Globulin is a measure of the sum of Immunoglobulins, plus inflammatory markers. It includes IgG, IgA, IgM, Fibrinogen, Complement, Caeruloplasmin, CRP etc.

Albumin: Globulin Ratio

Typically measured on urine for kidney disease, but serum ratio can highlight inflammatory responses.

Table: Functional Reference Ranges are described as reference ranges for optimal health.

When Liver Function Tests are Abnormal

Picture of 2 livers with a fatty liver being shown from heavy alcohol intake and a healthy liver shown by eating a good diet.
Alcohol has a negative effect on the liver while a healthy diet has a positive effect.

If viral infections have been ruled out, then consider:

  • Are you overweight? Are you skinny obese - check with an ultrasound.

  • What is your diet and lifestyle like?

  • Have you been taking any medications, herbs, drinking excess alcohol?

  • Do you have heavy metal exposure (Leaking dental amalgams, Lead etc)?

  • Do you have mould exposure?

  • Do you have male hormones (androgen) excess (ALT>33). In females this may appear as facial hair, acne, oily skin, menstrual periods extremely irregular. In males this may appear as androgen reduction with elevated female hormones (Oestrogen) with Gynaecomastia (breasts).

Unconjugated versus Conjugated Bilirubin in Babies

Did you know that should newborn babies exhibit signs of jaundice, they are tested for Unconjugated and Conjugated Bilirubin. Unconjugated Bilirubin is from the normal breakdown of RBC's that gets processed by the liver. As the newborns liver may take a few days to function properly, jaundice is sometimes seen. Conjugated bilirubin is also tested to rule out a rare complication - Biliary Atresia. That heel prick that babies get is very important not only for bilirubin, but for screening of other rare, but serious conditions.

To protect your liver, ensure you have a nutritious diet and be mindful of your lifestyle choices. Make sure your detoxification channels are open (review my other blogs on that). If you would like to discuss your personal circumstances, or have your pathology results reviewed in line with your current situation, feel free to make a booking with me on the bookings tab on my website.

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