Liver function tests (LFTs) measure liver injury, rather than liver function. They are a group of blood tests that measure substances in the blood that reflect whether the liver has been injured and the extent of the injuries. Sometimes these tests are also called a liver panel. The tests usually include the following: alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), albumin, total protein, and total and direct bilirubin.

The liver is a complex organ, located in the upper right corner of the abdomen, which has many vital roles. The liver stores fuel for the body that has been produced from sugars, and it is involved in the processing of fats and proteins. Bile produced by the liver is involved in the digestion and absorption of fat in the intestines. The liver also makes proteins that are essential for blood clotting, and it helps remove poisons and toxins from the body.

When a blood sample is collected from a child to measure LFTs, the skin is cleaned with alcohol first, then a needle is inserted into a vein and blood is drawn into specific tubes. These blood samples are then sent to a laboratory and processed by machines. The tests are done simultaneously, which takes about 20 minutes. Emergency test results are reported within an hour. For routine tests processed at the site of collection, results are usually available within 3 to 6 hours. If samples are shipped to a central processing facility, they are usually available the next day.

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