What Is a Blood Test? A blood test is when a sample of blood is taken from the body to be tested in a lab. Doctors order blood tests to check things such as the levels of glucose, hemoglobin, or white blood cells. This can help them detect problems like a disease or medical condition. Sometimes, blood tests can help them see how well an organ (such as the liver or kidneys) is working. What Is a Hepatic (Liver) Function Panel? A liver function panel is a blood test that helps doctors check for liver injury, infection, or disease. Liver function panels also can check for side effects in the liver from some medicines. Why Are Liver Function Panels Done? A liver function panel is done to learn information about the levels of: Albumin and total protein, which help build and maintain muscles, bones, blood, and organ tissue. Low levels may be seen with liver disease or kidney disease, or nutritional problems. Liver enzymes: Alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). These enzymes help the liver turn food into energy. When their levels are high, it can be a sign of that the liver is injured or irritated. Bilirubin. Bilirubin is made when red blood cells break down. The liver changes the bilirubin so that it can be excreted from the body. High bilirubin levels may mean there is a problem with the liver. This can make skin look yellow, a condition called jaundice. How Should I Prepare for a Liver Function Panel? You may be asked to stop eating and drinking for 8 to 12 hours before the test. Tell your doctor about any medicines you take because some drugs might affect the test results. It can help to wear a T shirt or other short-sleeve top on the day of the test to make things faster and easier for the technician who will be drawing the blood. How Is a Liver Function Panel Done? Most blood tests take a small amount of blood from a vein. To do that, a health professional will: clean the skin put an elastic band (tourniquet) above the area to get the veins to swell with blood insert a needle into a vein (usually in the arm inside of the elbow or on the back of the hand) pull the blood sample into a vial or syringe take off the elastic band and remove the needle from the vein It's best to try to relax and stay still during the procedure because tensing muscles can make it harder and more painful to draw blood. And if you don't want to watch the needle being inserted or see the blood collecting, you don't have to. Look the other way and maybe relax by focusing on saying the alphabet backward, doing some breathing exercises, thinking of a place that makes you happy, or listening to your favorite music. How Long Does a Liver Function Panel Take? Most blood tests take just a few minutes. Occasionally, it can be hard to find a vein, so the health professional may need to try more than once. What Happens After a Liver Function Panel? The health professional will remove the elastic band and the needle and cover the area with cotton or a bandage to stop the bleeding. Afterward, there may be some mild bruising, which should go away in a few days. When Are Liver Function Panel Results Ready? Blood samples are processed by a machine, and it may take a few hours to a day for the results to be available. If the test results show signs of a problem, the doctor might order other tests to figure out what the problem is and how to treat it. Are There Any Risks From Liver Function Panels? A liver function panel is a safe procedure with minimal risks. Some people might feel faint or lightheaded from the test. A few teens have a strong fear of needles. If you're anxious, talk with the doctor before the test about ways to make the procedure easier. A small bruise or mild soreness around the blood test site is common and can last for a few days. Get medical care if the discomfort gets worse or lasts longer. If you have questions about the liver function panel, speak with your doctor or the health professional doing the blood draw. Back to Articles Related Articles 5 Tips for Surviving Shots If you're afraid of shots, you're not alone. Next time your doc asks you to roll up your sleeve, try these tips. Read More Blood Test (Video) These videos show what's involved in getting a blood test and what it's like to be the person taking the blood sample. Read More Questions to Ask Your Doctor You're probably used to answering your doctor's questions - not asking your own. But it's your body, so you should be able to ask your doctor questions about anything you'd like. Here are some ideas to get you started. Read More Hepatitis Hepatitis, an infectious liver disease, is more contagious than HIV. Find out about the different types of hepatitis. Read More Mononucleosis (Mono) It's sometimes called "the kissing disease," but kissing is just one of the ways that someone can catch mono. Read More Cancer Center Visit our Cancer Center for teens to get information and advice on treating and coping with cancer. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.