Liver function tests (LFTs) explained

The liver is one of the hardest-working organs you have — it processes nutrients, filters toxins, makes proteins and helps your blood clot. A liver function test (LFT) is a group of blood markers that, read together, show how well the liver is coping. As with the kidneys, the liver can be under strain for a long time without obvious symptoms, so testing is a way to see what you otherwise could not.

The enzymes: ALT, AST and ALP

Enzymes are proteins that normally sit inside liver cells. When cells are stressed or inflamed, some of these enzymes leak into the blood, so raised levels can be an early signal worth investigating.

• ALT (alanine aminotransferase) — fairly specific to the liver.
• AST (aspartate aminotransferase) — found in the liver and elsewhere, read alongside ALT.
• ALP (alkaline phosphatase) — relates to the liver’s bile ducts and also to bone.

Bilirubin

Bilirubin is a yellow pigment made when old red blood cells are broken down; the liver processes and clears it. When bilirubin builds up, it can show as jaundice — a yellowing of the eyes or skin. It is one of the markers that tells you about the liver’s processing capacity.

Albumin and proteins

Albumin is a protein the liver makes, and it helps keep fluid in the right place and carries substances around the body. Because the liver produces it, albumin gives a sense of the liver’s manufacturing side, as opposed to the enzymes that flag stress.

Why read them together

No single liver marker tells the whole story — the pattern across enzymes, bilirubin and albumin is what matters. That is a job for a clinician, which is why every ProGen Health result set is reviewed and explained rather than handed over as raw numbers.