Alanine Aminotransferase, or ALT, is an enzyme predominantly found within liver cells, though smaller amounts exist in the kidneys and other organs. An ALT blood test measures the level of this enzyme in the bloodstream. Healthcare providers use this measurement as a marker to evaluate liver health. The concentration of ALT in the blood can shift when the liver is damaged, making it a frequent component of broader evaluations like a liver enzyme panel or a comprehensive metabolic panel (CMP).
Defining Low ALT Levels
When you receive blood test results, they will include a “normal range” for ALT, which can vary between laboratories due to different equipment and techniques. A common reference range is between 7 and 56 units per liter (U/L), with levels often being slightly higher in men than in women. A result is considered low when it falls below the established normal range provided by the lab, often under 7 U/L.
Causes and Associations of Low ALT
A low reading for Alanine Aminotransferase (ALT) can indicate a healthy liver and is not a reason for concern. However, certain factors and conditions can be associated with lower-than-average levels.
One of the more direct links to low ALT is a deficiency in vitamin B6. This vitamin acts as a coenzyme, meaning it is necessary for ALT to function properly, so a deficiency can lead to decreased ALT activity.
Beyond specific nutrients, other factors can influence ALT levels. Research indicates that ALT levels naturally decrease as people get older. In some elderly individuals, very low ALT may be connected to age-related changes like declining nutrition or a reduction in muscle mass (sarcopenia). Studies have also noted an association between low ALT and chronic kidney disease.
Next Steps After Receiving Results
Receiving a lab result showing low Alanine Aminotransferase (ALT) should not lead to self-diagnosis. The most important step is to discuss the findings with the healthcare provider who ordered the test, as a single lab value provides only a small piece of information about your overall health.
A doctor will interpret your low ALT result within the broader context of your complete medical profile. This includes your other blood test results, personal medical history, and current health status. They will also consider factors like age, diet, and any medications you are taking.
In many cases, a low ALT result is not clinically significant and requires no follow-up. If a potential underlying cause warrants investigation, such as a suspected nutrient deficiency, your doctor may recommend additional tests.