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Metabolic

ALT (Alanine Aminotransferase)

In the UK, the standard clinical (NHS) reference range for ALT (Alanine Aminotransferase) is 0-41 U/L, with 10-26 U/L considered the performance-optimised range. A result within these ranges suggests typical status; only a qualified clinician can interpret an individual reading.

ALT (alanine aminotransferase) is an enzyme found primarily in liver cells. When the liver is damaged or inflamed, ALT leaks into the bloodstream — making it one of the most sensitive markers of liver health. ALT is more specific to the liver than AST, which is also found in muscle and heart tissue.

Last reviewed: 11 June 2026

Optimal Ranges

What is the optimal range for ALT?

Clinical (NHS) Range

0-41 U/L

U/L

Performance-Optimised Range

10-26 U/L

U/L

ALT (Alanine Aminotransferase) reference ranges (UK)
RangeValueUnit
Clinical (NHS) reference range0-41 U/LU/L
Performance-optimised range10-26 U/LU/L

The clinical range defines what is considered medically “normal” — broad enough to cover 95% of the population. The performance range reflects where research and clinical experience suggest most people feel and function at their best. A result in either range suggests typical status and is not a diagnosis; any individual reading should be interpreted by a qualified clinician.

Why It Matters

Why ALT matters for performance

Your liver is the body's detoxification centre, metabolising everything from alcohol and paracetamol to protein and hormones. Elevated ALT often appears long before symptoms — catching liver stress early is critical. For active men, ALT can be mildly elevated after intense exercise (particularly resistance training), so timing matters. More concerning elevations indicate fatty liver disease (NAFLD), which affects an estimated 25-30% of UK adults and is the leading cause of liver disease in the developed world. NAFLD is strongly linked to insulin resistance and visceral fat, making ALT a valuable metabolic screening marker.

Symptoms

What are the symptoms of low or high ALT?

Low / Deficiency

  • ALT that is too low is rare and generally not clinically significant

High / Excess

  • Often asymptomatic in early stages
  • Fatigue and malaise
  • Abdominal discomfort (right upper quadrant)
  • Nausea and loss of appetite
  • Jaundice (yellowing of skin/eyes) in severe cases

Dietary Sources

Which foods support ALT levels?

Reduce alcohol consumption (primary modifiable risk factor)Limit fructose and refined sugars (drive hepatic fat accumulation)Coffee (3-4 cups/day associated with lower ALT and reduced liver disease risk)Cruciferous vegetables — broccoli, cauliflower, Brussels sproutsOmega-3 fatty acids from oily fish

Supplementation

How do you improve ALT levels?

There are no supplements that directly lower ALT — the goal is to address the underlying cause. For fatty liver: weight loss of 5-10% body weight is the most effective intervention, combined with reduced sugar intake and regular exercise. Milk thistle (silymarin) is widely marketed for liver health but evidence is mixed; it may offer modest benefit in specific liver conditions. NAC (N-acetylcysteine) supports glutathione production and is used clinically for paracetamol overdose but evidence for general liver protection is limited. The best approach is lifestyle: moderate alcohol, healthy weight, regular exercise, and adequate sleep.

Testing

How is ALT tested in the UK?

ALT is measured from a blood sample. With Helvy, that means a finger-prick kit taken at home and posted to a UKAS-accredited UK laboratory, with results in around 5 days, reviewed by a qualified clinician. Your result is reported against both the clinical range (0-41 U/L) and the performance-optimal range (10-26 U/L), so you can see not just whether you are “normal” but whether you are optimal. If you make a change, retest after 8-12 weeks to confirm it worked.

Research

Key study

Global epidemiology of nonalcoholic fatty liver disease — meta-analytic assessment of prevalence, incidence, and outcomes

Younossi ZM, Koenig AB, Abdelatif D, et al.

Hepatology (2016)

DOI: 10.1002/hep.28431

Related Biomarkers

Metabolic

HbA1c (Glycated Haemoglobin)

Optimal: 20-34 mmol/mol (below 5.4%)

Metabolic

Cholesterol (Total, HDL, LDL & ApoB)

Optimal: ApoB: below 1.0 g/L, LDL: below 2.6 mmol/L, HDL: above 1.2 mmol/L

Inflammation

hs-CRP (High-Sensitivity C-Reactive Protein)

Optimal: Below 1.0 mg/L

Related Guides

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How to Read Your Blood Test Results

UK guide to understanding results

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This content is for educational purposes only and does not constitute medical advice. Your data suggests areas for optimisation, but any concerns should be discussed with a qualified healthcare professional. If your results flag values outside safe ranges, we recommend consulting your GP.