What does your liver blood test mean (LFTs)?
Most people get a blood test at some time or other, but what do the results actually mean and what are the doctors looking for? Understanding your blood tests properly can help you understand your own health better so you can stay as healthy as possible for as long as possible.
When it comes to your liver function tests (or LFTs) we’re mainly looking at your enzymes.
alanine transferase (ALT)
aspartate transferase (AST)
alkaline phosphatase (ALP)
gamma GT (GGT)
and bilirubin (which is not an enzyme)
Fortunately I’ve made a handy video which explains everything here:
To break things down in more detail I’ll tell you what we look for and then what that might mean.
Your Liver
Let’s first of all get to grips with what your liver is. An incredible organ that is like a factory for producing and breaking down all kinds of carbs, fats, proteins, hormones and other chemicals. The processes are carried out by liver cells called hepatocytes, and tiny enzymes tend to be the things either building things up or breaking them down.
Your liver markers can go up when there’s inflammation or damage to the liver. This could be due to being overweight (leading to fatty deposits in the liver), alcohol excess (or other toxic drugs), infections like hepatitis, a blockage issue - like if you have gallstones, some genetic issues and traumatic injury.
Bilirubin
A breakdown product from the red cells in your body. The liver processes (conjugates) bilirubin so that it can be excreted by the kidneys. This is kind of a yellowish substance so if you can’t excrete it easily or there’s too much of it it can cause your skin and the whites of your eyes to be a bit yellow. This is called ‘jaundice’.
Common causes for a high bilirubin include:
Gilbert’s Syndrome. A genetic and pretty harmless condition where the body produces too much bilirubin.
Haemolysis - where too many red blood cells are broken down too quickly. This could be due to medications, genetic conditions or severe infection.
Other syndromes and medications can stop the bilirubin being excreted properly and this also leads to a rise in bilirubin.
Transaminases (ALT, AST)
These enzymes breakdown and synthesize amino acids. When the liver is damaged these enzymes are released and their levels in your blood rise.
ALT is found mainly in the liver but also in the skeletal muscles. If there’s mild damage to the liver (think fatty liver disease or infection) then this enzyme level will rise. If you’re very sporty then it may also go up a bit.
Similarly AST is found in the liver but is also found in significant amounts in the heart and muscles. It will go up much more with exercise and muscle damage and also if you have a heart attack. If you’re just interested in the liver then ALT is probably the best marker to look at.
If the enzyme levels rise quite high then it might point towards fatty liver disease or alcoholic liver disease. If your levels shoot up really high then it can point to viral infections (hepatitis) or an ischaemic liver (bad news indeed!).
If you have fatty liver disease you can actually improve it over time through lifestyle measures, so tracking your LFTs over time could show that you’re reversing some of the damage done and leading a healthier lifestyle!
Alkaline phosphatase
ALP comes mainly from the cells lining your bile ducts, but it’s also found in bones. If you have a problem with your bile ducts - for example you have gallstones, hepatitis or cirrhosis, then alkaline phosphatase will rise up. It can also rise if there are any bone issues, so you need to take that into account too.
Gamme-GT
Gamma GT is another enzyme found in the liver. It too increases when your liver or bile ducts are damaged, and is especially useful for assessing liver damage due to alcohol excess or the toxic effects of some medications (like anti-fungal medications and anti-depressants)
Putting all your LFTs together, alongside a wider understand of your current health can help to form a picture about what might be causing your liver to be inflamed and what to do about it. Doctors might not be too worried about small rises, but it could be a warning shot for you to do something about your health, especially if you know that you’re overweight or you drink too much.