What Is ALT in a Blood Test? Understanding Normal Ranges and Results

ALT stands for alanine aminotransferase, an enzyme primarily found in the liver [1]. This enzyme helps speed up certain chemical reactions in the body [1]. Normally, ALT levels in the blood are low. However, when the liver is damaged or inflamed, ALT can leak into the bloodstream, resulting in higher levels [1].

Because ALT is closely tied to liver function, it is commonly used as a marker of liver health. Elevated levels may signal liver stress, injury, or disease, even before noticeable symptoms appear.

Your healthcare provider may request an ALT test to evaluate liver health, diagnose liver diseases, or monitor the effects of treatments that can affect the liver [1]. It’s often included in routine blood work or as part of a liver function panel for a more complete picture of your health.

While reference ranges may vary slightly between laboratories, a typical normal range for ALT is approximately 7 to 55 units per liter (U/L) [2].

Several factors may influence what is considered a “normal” ALT level, including:

• Age: Levels tend to be higher in younger individuals [3].
• Sex: Men generally have slightly higher levels compared to women [3].
• Body mass index (BMI): Obesity may slightly raise levels [4].

ALT Normal Range by Age and Gender

Age Group	Female (U/L)	Male (U/L)
<3 years	13 – 45	13 – 45
3 – 12 years	15 – 35	15 – 35
13 – 18 years	12 – 26	15 – 47
>18 years	10 – 49	10 – 49

Source: UNC School of Medicine [1]

Note: Always consult with your healthcare provider for interpretation of your specific test results.

Normal ALT Levels

If your ALT falls within the standard reference range, it generally suggests that your liver is functioning well [1]. However, lab ranges are not absolute, and “normal” can vary based on individual factors [1].

Elevated ALT Levels

Mildly elevated ALT levels may not necessarily indicate severe liver damage. Temporary increases can occur due to physical exertion, certain medications, or minor infections [1].

Significantly high ALT levels, however, may signal underlying liver conditions such as [5]:

• Nonalcoholic fatty liver disease (NAFLD)
• Chronic hepatitis B or C
• Alcohol-related liver disease
• Hemochromatosis (iron overload disorder)

Medications like statins, antibiotics, and pain relievers (acetaminophen) may also elevate ALT levels [5]. If your ALT level is elevated, your healthcare provider may recommend follow-up steps such as repeating the test after a few weeks or months, ordering additional blood work or imaging, reviewing your medications and alcohol intake, and referring you to a liver specialist if needed.

Low ALT Levels

While less common, low ALT levels are usually not a cause for concern. They may be seen in [2]:

• Severe liver damage where enzyme production decreases
• Vitamin B6 deficiency

If your ALT levels are high, there are proactive steps you can take to support your liver health:

• Maintain a healthy weight: Reducing body fat can significantly lower ALT levels [4].
• Limit alcohol consumption: Alcohol can inflame and damage liver cells [5].
• Review medications: Some prescriptions and over-the-counter drugs may affect liver enzymes [5]. Talk with your healthcare provider.
• Adopt a liver-friendly diet: Focus on vegetables, fruits, whole grains, and lean proteins while limiting saturated fats, refined sugars, and processed foods [6].
• Manage underlying health conditions: Conditions like diabetes and high cholesterol should be treated to help prevent liver complications [5].

Regular monitoring and lifestyle changes can often bring elevated ALT levels back into a healthier range.

ALT vs. AST: What’s the Difference?

Feature	ALT (Alanine Aminotransferase)	AST (Aspartate Aminotransferase)
Where it’s found	Primarily in the liver	Found in multiple organs, including the liver, heart, muscles, kidneys, and brain [7]
Function	Helps metabolize proteins	Also involved in amino acid metabolism across various tissues
Specificity to liver	More specific to liver health	Less specific—can reflect damage in other organs or tissues
What high levels may indicate	Often suggests liver damage or inflammation	May indicate liver issues, but can also be linked to muscle or heart damage
How tests are used	Used to assess liver health and monitor liver conditions	Often used alongside ALT to provide a broader picture of overall health
Common testing context	Both are typically included in liver function tests (LFTs), comprehensive metabolic panels (CMP), or hepatic function panels to evaluate liver health

Healthcare providers often order ALT and AST tests together to get a more complete understanding of liver function and identify potential underlying conditions.

Understanding your ALT levels is a crucial step in monitoring your liver health and overall wellness. Whether your results fall within the normal range or show signs of elevation, having access to reliable testing and clear information empowers you to take proactive steps.

For convenient, accurate, and private liver enzyme testing from the comfort of your home, consider Everlywell 360. With our easy-to-use at-home lab tests, you can monitor your health anytime and share results directly with your healthcare provider.

Frequently Asked Questions

What Is a Healthy ALT Range by Age?
Generally, a healthy ALT range for adults is 7–55 U/L; however, slight variations exist depending on age, sex, and laboratory methods [2].

Is a Low ALT Level Better Than a High One?
Very low ALT levels are typically not dangerous. However, extremely low readings could signal malnutrition or severe liver injury [2].

Can a High ALT Level Ever Be Harmless?
Yes, transient high ALT can result from muscle injury, intense exercise, or minor infections and may not indicate permanent liver damage [1].

What Is a Good ALT Level for Women?
A typical healthy ALT level for women is 13–49 U/L, slightly lower than for men [8].

Is an ALT Level of 70 Concerning?
An ALT level of 70 U/L is mildly elevated. While it may not indicate serious liver disease, it warrants discussion with a healthcare provider [2].

Which Medications Are Known to Increase ALT Levels?
Common medications include statins, isoniazid, pyrazinamide, rifampicin, ibuprofen, or dapsone [5].