Liver function tests

Liver function tests (LFTs), also called a liver panel, are blood tests that check how your liver is doing. They measure several things together. Enzymes called ALT (also known as SGPT), AST (SGOT), ALP and GGT are made mainly in the liver, and their levels can change when the liver is inflamed or the bile ducts are blocked. Bilirubin is a yellow waste product from old red blood cells, which the liver clears. Albumin is a protein the liver makes. Some panels also include total protein and prothrombin time (PT or INR), which shows how long the blood takes to clot.

A doctor may ask for LFTs to find out whether liver disease or damage is behind symptoms such as nausea, vomiting, tiredness, yellow eyes or skin (jaundice), tummy swelling or pain, dark urine, pale stools or itching. They also show how serious a known liver disease is, whether treatment is working, and whether a medicine is harming the liver. People at higher risk may be tested without symptoms, for example people with diabetes, extra weight, heavy alcohol use, a family history of liver disease or contact with hepatitis. Fatty liver disease is often found because raised liver enzymes turn up in a test done for another reason.

Your doctor or the lab will tell you whether to fast. Some labs ask for 10 to 12 hours without food or drink.

A liver blood test goes like this:

1. You sit down and roll up your sleeve. A soft strap may be tied around your upper arm.
2. A small needle goes into a vein, usually on the inside of the elbow. You may feel a brief sting.
3. Blood runs into a small tube. This usually takes under five minutes.
4. The tube is sent to the lab.

A small bruise or some swelling may appear where the needle went in, and it should fade within a few days. Results usually take a few days, and most come within a few weeks. Ask when and how you will get yours. If you have heard nothing after a few weeks, contact the doctor who sent you.

Liver function tests carry very little risk. You may have slight pain or bruising where the needle went in, and this usually fades quickly. If you are worried about needles, tell the person taking your blood.

Your report lists each result next to the lab's own normal range, which depends on age, sex and the method the lab uses. Compare your result only with the range on your own report. A result outside the range does not always mean a liver problem. For example, a high ALP can come from bone disease as well as the liver, and results can be abnormal for a while after a recent illness, so your doctor may repeat the tests.

LFTs alone usually cannot name the disease. Your doctor looks at the pattern across all the results, with your symptoms, history and medicines. If the results are abnormal, more tests often follow. These can include blood tests for hepatitis B and C, an ultrasound, CT or MRI scan, and a test called elastography, which measures liver stiffness to look for scarring (fibrosis). A liver biopsy, in which a small piece of liver is looked at under a microscope, is kept for when other tests do not give a clear answer.