ALT (Alanine Aminotransferase)

Blood

Comprehensive Metabolic Panel (CMP)

ALT (alanine aminotransferase) is an enzyme concentrated in liver cells, and it is the most specific routine marker of liver cell injury. When liver cells are stressed or damaged, they release ALT into the blood, so a preventive practice watches it closely as an early window into metabolic and liver health.

What It Measures

Liver enzyme; most specific marker for liver cell damage

Optimal vs. Lab Range

Longevity Optimal

<25 U/L (M), <22 U/L (F)

Target range for optimal health and longevity based on research.

Standard Lab

7–56 U/L

Population-based reference range from standard labs.

Why It Matters

ALT is one of the clearest signals of liver stress, and in modern practice a rising value most often reflects fatty liver disease driven by metabolic dysfunction. Elevations can also come from hepatitis, medication toxicity, or alcohol use, and because fatty liver tracks with insulin resistance and metabolic syndrome, ALT doubles as an early metabolic warning light for healthspan. A low ALT is rarely clinically meaningful on its own. Even values within the standard laboratory range can be higher than optimal, which is why longevity-focused care looks at the tighter target rather than simply confirming you are inside the reference interval.

When Low

Rarely clinically significant when low

When High

Fatty liver (NAFLD), hepatitis, medication toxicity, alcohol use, metabolic syndrome

How to Optimize

The most effective lever for an elevated ALT is reversing the metabolic drivers of fatty liver through weight management, reducing refined carbohydrates and added sugars, and improving insulin sensitivity with regular exercise. Limiting or eliminating alcohol removes a major source of ongoing liver stress, and reviewing medications and supplements with a clinician can identify contributing agents. Broader metabolic optimization tends to bring ALT down as the liver recovers. It is best interpreted alongside AST, GGT, and markers of glucose control. Targets and treatment are individualized with your physician; this content is educational and not a substitute for medical advice.

Key Interventions & Linked Compounds

Strong evidence

Key Interventions

Liver support

NAFLD reversal

alcohol cessation

metabolic optimization

Linked Compounds & Supplements

NAC

Milk thistle

Berberine

Omega-3

Curated from clinical literature. Individual results vary; consult a qualified clinician before changing a protocol.

Ordering Notes

Specimen

Serum or plasma (venous draw)

Patient prep

No fasting required. Maintain usual diet and medications unless advised.

Recommended cadence

Annual

Reporting unit

Confirm with the performing lab — units vary by region.

Pre-analytic notes

Standardize draw time of day, hydration, and recent exercise. Note any acute illness, supplements, or hormonal therapies on the requisition.

Recommended Follow-Up Actions

1
Confirm the result is reliable
Repeat abnormal values before acting — preferably from the same lab, same time of day, and under consistent prep. Rule out acute illness, recent intense exercise, or medication effects that can shift ALT (Alanine Aminotransferase).
2
Compare against optimal, not just lab range
Use the optimal window above as the target. Lab "normal" is built from the general population and often misses early dysfunction.
3
Pair with related markers
Order a complementary panel covering metabolic, inflammatory, and hormonal context to interpret this marker properly.
4
Discuss interventions with a clinician
Use the interpretation guidance above to frame the conversation. Bring trends, not just one datapoint, to your visit.
5
Re-test on a defined cadence
If a change is implemented, re-measure in 8–12 weeks for fast-moving markers, or 3–6 months for slower ones, to confirm response before escalating.