Alanine Transaminase (ALT)

Alanine transaminase is a liver enzyme involved in a number of chemical reactions important to the production of energy. ALT labs are useful in the diagnosis and management of certain liver diseases, as significant elevations of ALT occur only in diseases of the liver.

Lab values are reported in units per liter (U/L).

The normal range for ALT changes with age.

Male (U/L)

• <1 Month 3-25
• 1-11 Months 4-35
• 1-3 Years 5-30
• 4-12 Years 8-30
• 13-15 Years 7-32
• 16-19 Years 8-46
• ≥20 Years 9-46

Female (U/L)

• <1 Month 3-25
• 1-11 Months 3-30
• 1-3 Years 5-30
• 4-12 Years 8-24
• 13-15 Years 6-19
• 16-19 Years 5-32
• ≥20 Years 6-29

Blood draw

Fasting is not required before the test.

Higher than normal lab values found in blood samples often mean recent or ongoing liver damage as a result of hepatitis, diabetes, injury, or other reasons. A more specific cause of the damage can be found by comparing ALT with other liver tests. This damage is not always apparent on other tests including imaging procedures like X-rays and MRIs.