Liver Function Tests Explained: ALT, AST, Bilirubin & More in Palm Beach County, FL

What it involves

MedlinePlus describes liver function tests, also called a liver panel, as blood tests that measure several substances made by or processed in the liver. Some show how well the liver is working and others show whether it may be damaged. The tests usually cannot name a specific disease on their own, so an unusual result is a reason for a conversation and often a second test, not a diagnosis.

Who this is for

• Patients who received a lab report with ALT, AST, or bilirubin on it and want it explained in plain words
• Patients who take medicines that their provider wants to monitor for effects on the liver
• Patients with diabetes, obesity, or a family history of liver disease
• Patients with unexplained tiredness, nausea, or yellowing of the skin or eyes

What to expect

• A review of your symptoms, medicines, alcohol use, and family history
• A blood draw, which MedlinePlus says takes less than five minutes
• Each number explained, along with which ones were abnormal and which were not
• A decision on whether to repeat the test or order something more specific

What a liver panel measures

MedlinePlus lists the common parts of a liver panel:

• Albumin and total protein, proteins mostly made in the liver
• ALT, AST, ALP, and GGT, enzymes that are mainly made in the liver
• Bilirubin, a waste product from old red blood cells that the liver removes
• LDH, an enzyme found in many tissues, with large amounts in the liver
• Prothrombin time, which shows how long the blood takes to clot

Why a provider orders it

MedlinePlus says liver tests are most often used to find out whether liver disease or damage could be causing symptoms, to learn how serious a known liver disease is, to monitor it over time, and to check for side effects of certain medicines. Many of these tests are also bundled into a comprehensive metabolic panel, which is often drawn at a routine checkup, so you may see liver numbers even when nobody suspected a problem. Liver function tests also appear on the list of blood tests MedlinePlus names for swollen lymph nodes, which the swollen lymph nodes guide describes in plain terms.

Symptoms and risks that make testing more likely

MedlinePlus lists symptoms that can point toward the liver, including nausea and vomiting, loss of appetite, fatigue, weakness, jaundice, belly pain or swelling, swollen ankles and legs, dark urine, pale stool, and frequent itching. It also names higher-risk groups who may be tested without symptoms, such as people with a family history of liver disease, alcohol use disorder, obesity, diabetes, or hepatitis, and people taking medicines that can affect the liver. Belly pain or swelling is one symptom that can point toward the liver, and the abdominal pain guide describes the other causes of pain in that area. Bilirubin and liver tests are among the blood tests MedlinePlus says may be ordered for gallstones, as the gallstones guide explains.

Preparing for the blood draw

MedlinePlus says you will probably need to fast for 10 to 12 hours before a liver panel, and that you should tell your provider about every medicine you take because some can change the results. Do not stop a medicine on your own. The fasting blood work preparation guide covers what fasting means in practice, including water and morning appointments.

What an abnormal result can and cannot mean

MedlinePlus says the pattern across all the substances matters more than any single number, because different patterns suggest different problems, such as liver inflammation, trouble with the bile ducts, or harm from a medicine. It also says abnormal results do not always mean a liver problem. High ALP, for example, can come from bone disease as well as liver disease, and results can be temporary after a recent illness, so a provider may simply repeat the test later.

Liver results next to the rest of your health

Liver numbers are rarely read alone. A provider looks at them with your kidney results, which the kidney function tests guide explains, and with blood sugar if you have diabetes. Patients who have gained weight without an obvious reason may also have this blood work included in the unexplained weight gain evaluation.

Sources

• MedlinePlus — Liver Function Tests