A blood sample is needed. For information on how this is done, see: Venipuncture
How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
This test is used to determine if a patient has liver damage.
Normal range can vary according to a number of factors, including age and gender. Normal value ranges may also vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean
Increased levels of ALT often means that liver disease is present. Liver disease is even more likely when levels of other liver blood tests are also increased.
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
Bleeding from where the needle was inserted
Fainting or feeling light-headed
Hematoma (blood collecting under the skin)
Berk PD, Korenblat KM. Approach to the patient with jaundice or abnormal liver test results. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 150.
Pratt DS. Liver chemistry and function tests. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier;2010:chap 73.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.