ALT: what your result means.

Alanine aminotransferase (ALT) is a liver enzyme released into blood when liver cells are stressed or damaged. It is the front-line blood marker of liver health, and of metabolic-associated fatty liver disease in particular.

Why ALT matters

Fatty liver disease now affects roughly one in four adults globally, mostly silently. ALT rises early in that process, and research shows that even values in the upper part of the traditional 'normal' range carry meaning, which is why evidence-based interpretation uses tighter, sex-specific healthy thresholds.

Associated risks when out of range: Fatty liver. Metabolic dysfunction.

What the clinical evidence shows

The evidence base behind how the HodieLabs Evidence-Based Clinical Library interprets ALT, from randomised trials, prospective cohorts and genetic (Mendelian randomisation) studies. Full citations in the reference list below.

• Updated healthy ALT thresholds (Prati et al. Annals of Internal Medicine 2002): in ~6,800 rigorously screened blood donors, truly healthy ALT ranges were substantially lower than traditional laboratory limits, the basis for the tighter, sex-specific thresholds evidence-based practice now uses.
• Global NAFLD epidemiology (Younossi et al. Hepatology 2016): meta-analysis across 22 countries put fatty liver disease prevalence at ~25% of the world's adults, the most common liver condition in history, and largely silent.
• Long-term NAFLD outcomes (Ekstedt et al. Hepatology 2015): over ~26 years of follow-up, fibrosis stage, not symptoms, predicted mortality in fatty liver disease, underlining why early biochemical detection and metabolic action matter.

Evidence-based reference ranges

The HodieLabs Evidence-Based Clinical Library interprets ALT against published clinical authority standards, never arbitrary "optimal" ranges. Measured in U/L:

Band	Range (U/L)
Optimal	Male: <30; Female: <19 U/L
Borderline	Male: 30–40; Female: 19–30 U/L
High	Male: 41–100; Female: 31–100 U/L
Very high	>100 U/L

Clinical interpretation

• The most liver-specific of the transaminases; mild elevation is common with NAFLD.
• Very low ALT (<10 U/L) in older adults may paradoxically indicate sarcopenia or frailty.
• ALT within normal range does not exclude liver fibrosis. Consider FibroScan if clinical suspicion.

What improves it: the evidence-based levers

• Reduce visceral fat
• Reduce alcohol
• Improve insulin sensitivity

Recommended testing frequency: Annual, as part of a comprehensive panel. Single markers are always interpreted in context.

How ALT testing works at HodieLabs

ALT is measured in every Health Blueprint at our Melbourne Preventative Health & Longevity Clinic, interpreted by a doctor against the guideline-cited ranges above and tracked over time through your HodieLabs membership.

References

1. Prati D, et al. Updated definitions of healthy ranges for serum alanine aminotransferase levels. Ann Intern Med. 2002;137:1–10.
2. Younossi ZM, et al. Global epidemiology of nonalcoholic fatty liver disease: meta-analytic assessment of prevalence, incidence, and outcomes. Hepatology. 2016;64:73–84.
3. Ekstedt M, et al. Fibrosis stage is the strongest predictor for disease-specific mortality in NAFLD after up to 33 years of follow-up. Hepatology. 2015;61:1547–1554.

This page is general information from the HodieLabs Evidence-Based Clinical Library, not medical advice. Speak with your GP about what testing and care is appropriate for you.