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Longevity Library · Lab reference

Written by Daniel Tagge, MD
Updated October 7, 2026
Reviewed October 10, 2026
25 sources · Measured in U/L

System: Metabolism & Metabolomics

ALTAlanine aminotransferase · SGPT

Laboratories print an ALT upper limit anywhere from about 40 to 65 U/L, but the gastroenterology guideline puts a true healthy normal at 29 to 33 U/L in men and 19 to 25 in women, and the largest cohort found liver-disease mortality already rising at 20 to 29 U/L. An ALT inside the printed range can still mean fat in the liver.

ALT is an enzyme that leaks out of liver cells when they are injured, and in most adults a raised value means fat in the liver rather than hepatitis. The printed reference range is wide because the people used to define it included many with undiagnosed fatty liver. Healthy-population studies put the upper limit near 30 in men and about 20 in women.

01 · The scale

Where the laboratory range and the evidence sit.

Liver-disease mortality rose from the 20s in the largest cohort, well inside every printed range. All-cause and cardiovascular mortality did not track ALT in US cohorts, while diabetes risk doubled from the lowest to the highest quarter and genetic evidence suggests that link is causal.

01020304050607080

  1. Common laboratory reference range

    7 to 65 U/L · Typical US laboratories; upper limit printed from about 40 to 65

  2. Lowest liver-disease mortality: under 20

    0 to 19 U/L · Kim 2004

  3. Guideline true-normal upper limits: 25 women, 33 men

    19 to 33 U/L · ACG 2017; AASLD 2023

  4. Men 9.5 times, women 6.6 times the liver-disease mortality of under 20

    30 to 39 U/L · Kim 2004

  5. Above most printed limits: higher liver-disease mortality

    40 and above U/L · Ruhl 2009; Lee 2008

  • Laboratory range
  • Evidence supports
  • Guideline goal or unstudied
  • Higher risk in studies
Scale in U/L. U/L is the same as IU/L. Bands show where studies found something, not a recommendation for any one person.

02 · What it is

What ALT measures.

ALT is one of the four standard liver chemistries, with AST, alkaline phosphatase and bilirubin. When liver cells are injured the enzyme leaks into the blood, and a rise in ALT and AST out of proportion to alkaline phosphatase is the laboratory definition of hepatocellular injury.1Grade A

In the United States the usual reason for a raised ALT is fat in the liver. Among adults in the national survey with an ALT above the healthy-population cutoffs, almost 90 percent of men and 83 percent of women had at least one risk factor for liver disease, nearly always overweight; the authors expected that the large majority had fatty liver related to body weight.2Grade B

That condition was renamed in 2023. A consensus of 236 experts and patient advocates from 56 countries replaced the term nonalcoholic fatty liver disease with metabolic dysfunction-associated steatotic liver disease, defined by liver fat plus at least one of five cardiometabolic risk factors, with a separate category for people who also drink more than about 140 to 350 grams of alcohol a week (women) or 210 to 420 (men).3Grade A

03 · The laboratory range

What a laboratory calls normal.

About 7 to 40 U/L at some laboratories and up to about 55 or 65 U/L at others, depending on the laboratory.

There is no generally accepted upper limit of normal for ALT in the United States, and the printed limits differ about twofold between laboratories (31 to 72 U/L across laboratories in one state). The principal reason is not the instruments but the reference populations: laboratories derived their ranges from people who were poorly characterized and often included people with undiagnosed liver disease, mostly fatty liver.2Grade B

When the range is recalculated from people at genuinely low risk, it shrinks. In 6,835 first-time Italian blood donors, ALT rose independently with body mass index and with markers of abnormal lipid and glucose metabolism; using only the lowest-risk donors, the upper limits came out at 30 U/L for men and 19 for women, against the 40 and 30 the laboratory had been printing. The lower limits found 76 percent of donors with hepatitis C viremia instead of 55 percent, at a specificity of 88.5 percent instead of 97.4.4Grade B

In the US national survey, among 3,747 adults with no viral hepatitis, low alcohol intake, no diabetes and a normal weight and waist, the median ALT was 21 U/L in men and 17 in women. The cutoffs that best separated them from people with hepatitis C were 29 U/L for men and 22 for women. Applied to the whole population, those cutoffs would call 36.4 percent of US men and 28.3 percent of women abnormal, which is the real reason laboratories keep the higher limits.2Grade B

The American College of Gastroenterology guideline on abnormal liver chemistries states that a true healthy normal ALT ranges from 29 to 33 U/L in men and 19 to 25 U/L in women, and that levels above this should be assessed. The liver-society guidance on fatty liver repeats the same figures and notes that the normal values most laboratories provide are higher than what should be considered normal.1,5Grade A

The same problem exists in children. Across US children's hospitals the median ALT upper limit was 53 U/L (range 30 to 90), while the 95th percentile in healthy-weight, metabolically normal children in the national survey was 25.8 U/L in boys and 22.1 in girls. The hospital thresholds detected only 32 to 48 percent of children with fatty liver or viral hepatitis; the survey-derived thresholds detected 72 percent of boys and 82 percent of girls.6Grade B

04 · The evidence

What the studies support.

In 94,533 Korean men and 47,522 women aged 35 to 59 followed for 8 years, liver-disease mortality rose with ALT inside the laboratory's normal range. Compared with an ALT under 20 U/L, men at 20 to 29 had 2.9 times the adjusted risk of dying of liver disease and men at 30 to 39 had 9.5 times; women had 3.8 and 6.6 times. The cutoff that best predicted liver-disease death in men was 30 U/L. An association in one national cohort where viral hepatitis was common, not proof that the enzyme itself does harm.7Grade B

In 14,950 US adults without hepatitis B or C followed for 12 years, an ALT above 30 U/L in men or 19 in women carried 8.2 times the risk of death from liver disease but was not associated with death from all causes (hazard ratio 1.2, confidence interval 0.88 to 1.6), cardiovascular disease or cancer. Liver disease caused only 0.13 percent of the deaths, so the enzyme's clearest signal is for a rare outcome.8Grade B

Among 6,823 residents of one Minnesota county who had an ALT measured during routine care, 13 percent were above the laboratory limit; those at one to two times the limit had a standardized mortality ratio of 1.21 and those above twice the limit 1.51, after excluding deaths in the first two years. People with a normal ALT died at 61 percent of the expected rate.9Grade B

Pooled across cohorts the all-cause mortality signal is inconsistent. A meta-analysis of 19 cohorts with over 9.24 million participants found the top third of ALT carried a lower all-cause mortality than the bottom third in North American populations (relative risk 0.82) and a higher one in Asian populations (1.43). A separate meta-analysis of 12 cohorts (206,678 participants) found that in older adults each 5 U/L of ALT was associated with 9 percent lower all-cause and cardiovascular mortality, so that a very low ALT in older people marked frailty rather than health.10,11Grade B

ALT predicts type 2 diabetes. In a meta-analysis of 21 prospective population studies, each unit of log ALT carried a fully adjusted hazard ratio of 1.83 for new diabetes, and the top fourth of the ALT distribution had 2.02 times the risk of the bottom fourth; fatty liver seen on ultrasound more than doubled the risk. A Mendelian randomization study using genetic variants that raise ALT found 2.99 times the odds of diabetes per doubling of ALT, which argues that the liver fat ALT reflects is on the causal path, while the same genetic signal was not clearly linked to coronary disease (odds ratio 0.74, confidence interval 0.54 to 1.01).12,13Grade B

In the liver-society guidance on fatty liver, an ALT or AST that stays above 30 U/L, chronically for 6 to 12 months or intermittently, may indicate chronic liver injury, and a fall in ALT tracks histological improvement: ALT normalization predicts resolution of steatohepatitis with lifestyle change or treatment.5Grade A

05 · What moves it

The levers with evidence behind them.

What is listed here has been tested. The size of each effect, and the size of the study, are in the sentence, so a small effect reads as a small effect.

  • Weight loss of 5 to 10 percent

    lowers it and clears liver fat

    In 293 adults with biopsy-proven steatohepatitis who followed lifestyle advice for 52 weeks, 58 percent of those who lost 5 percent or more of their weight had resolution of steatohepatitis, and among those who lost 10 percent or more, 90 percent had resolution and 45 percent had regression of fibrosis. Only 30 percent reached the 5 percent mark. The liver-society guidance summarizes it as: 3 to 5 percent weight loss improves steatosis, more than 10 percent is generally needed to improve steatohepatitis and fibrosis.14,5Grade A

  • Exercise, even without weight loss

    lowers liver fat; ALT change smaller and unproven

    Pooling 12 controlled trials, regular aerobic or resistance exercise reduced liver fat compared with no exercise (effect size -0.37) with minimal or no weight loss and at volumes below the usual recommendations for obesity. The pooled effect on ALT itself was not significant (effect size -0.15), so the enzyme can lag behind the liver fat it reflects.15Grade A

  • Mediterranean diet

    lowers liver fat without weight loss

    In a 6-week randomized crossover trial of 12 people with biopsy-proven fatty liver, a Mediterranean diet cut liver fat on magnetic resonance spectroscopy by 39 percent against 7 percent on a low-fat, high-carbohydrate diet, with no difference in weight loss, and improved insulin sensitivity on clamp testing. A small trial with gold-standard measurements; the liver-society guidance recommends the diet for its liver and cardiovascular benefits.16,5Grade B

  • Sugar-sweetened drinks and excess fructose

    raise it when they add calories

    Across 51 controlled feeding trials (2,059 participants), sugar-sweetened beverages added on top of the usual diet raised liver fat (standardized mean difference 1.72) and raised ALT by a mean of 3.09 U/L across 12 trials, about 11 percent, with a linear dose response. When the same sugars replaced other calories at matched energy, neither liver fat nor ALT changed, so the harm is from the excess energy sugar makes easy to drink.17Grade A

  • Alcohol

    raises it, in proportion to intake and to bingeing

    In 19,225 Finnish adults, regular alcohol intake was roughly linearly related to ALT and GGT, and bingeing more than once a month raised both markedly even in people whose overall consumption was low-risk. Under the 2023 nomenclature, liver fat in someone drinking above about 140 grams a week (women) or 210 (men) is classed as metabolic and alcohol-related disease, and the liver-society guidance notes that abstinence may lower the risk of fibrosis progression in fatty liver.18,3,5Grade B

  • Coffee

    lower ALT in drinkers of 3 or more cups a day

    Among 27,793 US adults in the national survey, those drinking 3 or more cups of coffee a day had 25 percent lower odds of an abnormal ALT than non-drinkers (odds ratio 0.75), and 2 or more cups of decaffeinated coffee carried 38 percent lower odds, so the effect is not the caffeine. A cross-sectional association; the liver-society guidance notes that 3 or more cups daily is associated with less advanced liver disease.19,5Grade C

06 · Reading it well

Caveats, and what belongs with a physician.

ALT is in muscle as well as liver. In 15 healthy men who did one hour of weightlifting they were not used to, AST, ALT, creatine kinase and myoglobin all rose significantly and stayed raised for at least 7 days. A draw within a week of hard or unfamiliar training can read as liver injury; a creatine kinase alongside sorts it out.20Grade C

A normal ALT does not exclude fatty liver, or even advanced disease. In 51 people with biopsy-proven fatty liver and a normal ALT, the histology matched that of 50 people with a raised ALT; 12 had bridging fibrosis and 6 had cirrhosis. A low-normal ALT under 30 U/L meant less fat but a similar rate of advanced fibrosis (5 of 15 versus 13 of 36). The guidance on fatty liver is explicit that the laboratory's normal is higher than the liver's.21,5Grade B

Women run lower than men at every level of risk: medians of 17 versus 21 U/L in low-risk US adults, healthy-population upper limits of 19 versus 30 in Italian blood donors, and a measurable sex difference in biological variation. A single cutoff for both sexes under-reads women.2,4,22Grade B

The number depends on the reagent. The international reference method adds pyridoxal phosphate (the active form of vitamin B6) to the assay, and its omission is the most frequent cause of biased aminotransferase results, yet only about one third of laboratories include it. Within one healthy person ALT also varies about 9 percent from week to week, so compare results from the same laboratory and watch the trend rather than one value.23,22Grade C

The AST to ALT ratio helps with pattern, not with drinking history. Among 313 people admitted for alcohol withdrawal the ratio was 1.0 or less in 64 percent, while among 48 with alcohol-related cirrhosis 69 percent had a ratio of 2 or more; a high ratio suggests advanced liver disease rather than heavy drinking as such.24Grade C

An unexplained ALT is sometimes the gut. About 18.7 percent of adults newly diagnosed with celiac disease have raised liver enzymes, and they normalize on a gluten-free diet in 83.1 percent; among adults with unexplained raised liver tests, 4.5 percent had biopsy-proven celiac disease. The gastroenterology guideline's workup of a persistently raised ALT also covers hepatitis B and C, iron overload, autoimmune hepatitis, Wilson's disease, alpha-1 antitrypsin deficiency and a review of prescription, over-the-counter and herbal products.25,1Grade A

See a physician

  • An ALT above about twice the laboratory's upper limit, or any ALT that stays raised on a repeat draw after a week without heavy exercise.
  • Any ALT result alongside yellowing of the eyes or skin, dark urine, pale stools, or pain under the right ribs.
  • A raised ALT with alcohol intake above about one drink a day (women) or two (men), or with any recent new prescription, supplement or herbal product.
  • A raised ALT with a possible exposure to hepatitis B or C (a transfusion before 1992, injection drug use, a partner with hepatitis, birth in a region where hepatitis B is common), or with a family history of hemochromatosis or liver disease.
  • A raised ALT with diabetes, a large waist, high triglycerides or a high fasting insulin, which together make fatty liver with fibrosis more likely and call for a fibrosis estimate, not just a repeat enzyme.

This page is education, not individual medical advice, and reading it creates no physician-patient relationship.

07 · Open questions

What the literature does not settle.

  • No trial has treated healthy adults to an ALT target and measured outcomes; the guideline's 33 and 25 U/L are upper limits derived from low-risk populations and from where liver-disease mortality rose in one cohort, not a tested goal.
  • The liver-disease mortality curve comes mainly from a Korean cohort in which viral hepatitis was common; US cohorts show the liver signal but no all-cause mortality signal, and in older adults a low ALT marks frailty rather than health. Which parts transfer to a well, middle-aged American is unsettled.
  • ALT is a proxy for liver fat, and liver fat is the thing with outcome data. Whether lowering ALT without changing liver fat means anything is unknown, and exercise trials show the two can move separately.
  • The right sex-specific, assay-specific upper limits have not been agreed; healthy-population studies in Italy, the United States and France give upper limits for men anywhere from 29 to 44 U/L depending on who was excluded.

08 · In practice

How Dr. Tagge reads it in his own practice.

I read ALT against the guideline's healthy normal, under about 33 U/L in men and 25 in women, not against the laboratory's printed limit. A result in the high 30s or 40s that the report calls normal is, in most of the people I see, fat in the liver driven by the same insulin resistance showing up elsewhere on the panel, and it belongs with fasting insulin, triglycerides and waist size rather than in a drawer. One raised value after a hard week of training earns a repeat, not a label.

A practice judgment, labeled as one (Grade D): it is how one physician reads the number for the people he cares for, not a recommendation for you.

09

Questions

10 · Sources

25 sources, read in full.

Numbered in the order they appear. Each line says what this page relies on from the paper; the link opens the record at PubMed or the publisher.

  1. 1.

    Kwo PY, Cohen SM, Lim JK. ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. American Journal of Gastroenterology. 2017. PMID 27995906. DOI 10.1038/ajg.2016.517.

    Guideline · A true healthy normal ALT ranges from 29 to 33 IU/L in men and 19 to 25 IU/L in women; levels above this should be assessed, including for viral hepatitis, fatty liver, alcohol, hemochromatosis, autoimmune disease and medications.

  2. 2.

    Ruhl CE, Everhart JE. Upper limits of normal for alanine aminotransferase activity in the United States population. Hepatology. 2012. PMID 21987480. DOI 10.1002/hep.24725.

    Cross-sectional study · In NHANES, cutoffs of 29 U/L (men) and 22 U/L (women) best separated low-risk adults from hepatitis C; applied nationally they would call 36.4 percent of men and 28.3 percent of women abnormal.

  3. 3.

    Rinella ME, Lazarus JV, Ratziu V, et al.; NAFLD Nomenclature consensus group. A multisociety Delphi consensus statement on new fatty liver disease nomenclature. Hepatology. 2023. PMID 37363821. DOI 10.1097/HEP.0000000000000520.

    Consensus statement · NAFLD renamed metabolic dysfunction-associated steatotic liver disease, defined by steatosis plus at least one of five cardiometabolic risk factors; MetALD for intake of 140 to 350 g/week (women) or 210 to 420 g/week (men).

  4. 4.

    Prati D, Taioli E, Zanella A, et al.. Updated definitions of healthy ranges for serum alanine aminotransferase levels. Annals of Internal Medicine. 2002. PMID 12093239. DOI 10.7326/0003-4819-137-1-200207020-00006.

    Prospective cohort · In 6,835 first-time blood donors, ALT tracked body mass index and metabolic markers; lowest-risk donors gave upper limits of 30 U/L (men) and 19 U/L (women) against the 40 and 30 in use.

  5. 5.

    Rinella ME, Neuschwander-Tetri BA, Siddiqui MS, et al.. AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease. Hepatology. 2023. PMID 36727674. DOI 10.1097/HEP.0000000000000323.

    Guideline · Laboratory normals are higher than the true normal ALT of 29 to 33 U/L (men) and 19 to 25 (women); weight loss of 3 to 5 percent improves steatosis and over 10 percent is generally needed for steatohepatitis and fibrosis; Mediterranean diet and coffee are supported.

  6. 6.

    Schwimmer JB, Dunn W, Norman GJ, et al.. SAFETY study: alanine aminotransferase cutoff values are set too high for reliable detection of pediatric chronic liver disease. Gastroenterology. 2010. PMID 20064512. DOI 10.1053/j.gastro.2009.12.052.

    Cross-sectional study · Children's hospitals used a median ALT upper limit of 53 U/L (range 30 to 90); the 95th percentile in healthy children was 25.8 (boys) and 22.1 (girls), and hospital thresholds detected only 32 to 48 percent of liver disease.

  7. 7.

    Kim HC, Nam CM, Jee SH, Han KH, Oh DK, Suh I. Normal serum aminotransferase concentration and risk of mortality from liver diseases: prospective cohort study. BMJ. 2004. PMID 15028636. DOI 10.1136/bmj.38050.593634.63.

    Prospective cohort · In 94,533 men and 47,522 women, ALT of 20 to 29 and 30 to 39 U/L carried 2.9 and 9.5 times the liver-disease mortality of under 20 in men (3.8 and 6.6 in women); best cutoff in men 30 U/L.

  8. 8.

    Ruhl CE, Everhart JE. Elevated serum alanine aminotransferase and gamma-glutamyltransferase and mortality in the United States population. Gastroenterology. 2009. PMID 19100265. DOI 10.1053/j.gastro.2008.10.052.

    Prospective cohort · In 14,950 NHANES III adults over 12 years, ALT above 30 (men) or 19 (women) carried 8.2 times the liver-disease mortality but no excess all-cause, cardiovascular or cancer mortality.

  9. 9.

    Lee TH, Kim WR, Benson JT, Therneau TM, Melton LJ 3rd. Serum aminotransferase activity and mortality risk in a United States community. Hepatology. 2008. PMID 18302294. DOI 10.1002/hep.22090.

    Prospective cohort · Among 6,823 Olmsted County residents, ALT at 1 to 2 times the upper limit carried a standardized mortality ratio of 1.21 and above 2 times 1.51; normal ALT 0.61.

  10. 10.

    Kunutsor SK, Apekey TA, Seddoh D, Walley J. Liver enzymes and risk of all-cause mortality in general populations: a systematic review and meta-analysis. International Journal of Epidemiology. 2014. PMID 24585856. DOI 10.1093/ije/dyt192.

    Systematic review and meta-analysis · Across 19 cohorts (over 9.24 million participants), the top third of ALT carried a relative risk of all-cause mortality of 0.82 in North American and 1.43 in Asian populations.

  11. 11.

    Liu Z, Ning H, Que S, Wang L, Qin X, Peng T. Complex association between alanine aminotransferase activity and mortality in general population: a systematic review and meta-analysis of prospective studies. PLoS One. 2014. PMID 24633141. DOI 10.1371/journal.pone.0091410.

    Systematic review and meta-analysis · In 12 cohorts (206,678 participants), each 5 U/L of ALT carried 1.24 times the liver-disease mortality in younger adults, but 0.91 times the all-cause and cardiovascular mortality in older adults.

  12. 12.

    Fraser A, Harris R, Sattar N, Ebrahim S, Davey Smith G, Lawlor DA. Alanine aminotransferase, gamma-glutamyltransferase, and incident diabetes: the British Women's Heart and Health Study and meta-analysis. Diabetes Care. 2009. PMID 19131466. DOI 10.2337/dc08-1870.

    Systematic review and meta-analysis · Across 21 prospective studies, the fully adjusted hazard ratio for diabetes was 1.83 per unit of log ALT and 2.02 for the top versus bottom fourth; ultrasound fatty liver more than doubled the risk.

  13. 13.

    Liu J, Au Yeung SL, Lin SL, Leung GM, Schooling CM. Liver Enzymes and Risk of Ischemic Heart Disease and Type 2 Diabetes Mellitus: A Mendelian Randomization Study. Scientific Reports. 2016. PMID 27996050. DOI 10.1038/srep38813.

    Mendelian randomization · Genetically higher ALT carried 2.99 times the odds of diabetes per 100 percent change in concentration, and was not clearly associated with coronary disease (odds ratio 0.74, 0.54 to 1.01).

  14. 14.

    Vilar-Gomez E, Martinez-Perez Y, Calzadilla-Bertot L, et al.. Weight Loss Through Lifestyle Modification Significantly Reduces Features of Nonalcoholic Steatohepatitis. Gastroenterology. 2015. PMID 25865049. DOI 10.1053/j.gastro.2015.04.005.

    Prospective cohort · In 293 adults with biopsy-proven steatohepatitis, weight loss of 5 percent or more gave 58 percent resolution and 10 percent or more gave 90 percent resolution with 45 percent fibrosis regression over 52 weeks.

  15. 15.

    Keating SE, Hackett DA, George J, Johnson NA. Exercise and non-alcoholic fatty liver disease: a systematic review and meta-analysis. Journal of Hepatology. 2012. PMID 22414768. DOI 10.1016/j.jhep.2012.02.023.

    Systematic review and meta-analysis · Across 12 trials, exercise reduced liver fat versus control (effect size -0.37) with minimal or no weight loss, but did not significantly change ALT (effect size -0.15).

  16. 16.

    Ryan MC, Itsiopoulos C, Thodis T, et al.. The Mediterranean diet improves hepatic steatosis and insulin sensitivity in individuals with non-alcoholic fatty liver disease. Journal of Hepatology. 2013. PMID 23485520. DOI 10.1016/j.jhep.2013.02.012.

    Randomized trial · In a 6-week crossover trial of 12 people with fatty liver, a Mediterranean diet reduced liver fat by 39 percent versus 7 percent on a low-fat, high-carbohydrate diet, without weight-loss differences.

  17. 17.

    Lee D, Chiavaroli L, Ayoub-Charette S, et al.. Important Food Sources of Fructose-Containing Sugars and Non-Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis of Controlled Trials. Nutrients. 2022. PMID 35889803. DOI 10.3390/nu14142846.

    Systematic review and meta-analysis · Across 51 controlled trials (2,059 participants), sugar-sweetened beverages adding excess energy raised liver fat (SMD 1.72) and ALT (mean difference 3.09 U/L); at matched energy, sugars had no effect.

  18. 18.

    Nivukoski U, Bloigu A, Bloigu R, Aalto M, Laatikainen T, Niemelä O. Liver enzymes in alcohol consumers with or without binge drinking. Alcohol. 2019. PMID 30890357. DOI 10.1016/j.alcohol.2019.03.001.

    Cross-sectional study · In 19,225 Finnish adults, regular alcohol intake was roughly linearly related to ALT and GGT, and binge drinking more than once a month raised both markedly even at low-risk overall intake.

  19. 19.

    Xiao Q, Sinha R, Graubard BI, Freedman ND. Inverse associations of total and decaffeinated coffee with liver enzyme levels in National Health and Nutrition Examination Survey 1999-2010. Hepatology. 2014. PMID 25124935. DOI 10.1002/hep.27367.

    Cross-sectional study · Among 27,793 US adults, 3 or more cups of coffee a day carried an odds ratio of 0.75 for abnormal ALT; 2 or more cups of decaffeinated coffee 0.62.

  20. 20.

    Pettersson J, Hindorf U, Persson P, et al.. Muscular exercise can cause highly pathological liver function tests in healthy men. British Journal of Clinical Pharmacology. 2008. PMID 17764474. DOI 10.1111/j.1365-2125.2007.03001.x.

    Randomized trial · In 15 healthy men, one hour of weightlifting raised AST, ALT, creatine kinase and myoglobin significantly for at least 7 days.

  21. 21.

    Mofrad P, Contos MJ, Haque M, et al.. Clinical and histologic spectrum of nonalcoholic fatty liver disease associated with normal ALT values. Hepatology. 2003. PMID 12774006. DOI 10.1053/jhep.2003.50229.

    Cross-sectional study · In 51 people with fatty liver and a normal ALT, the histologic spectrum matched 50 with a raised ALT; 12 had bridging fibrosis and 6 cirrhosis, and a low-normal ALT did not exclude advanced fibrosis.

  22. 22.

    Carobene A, Røraas T, Sølvik UØ, et al.; European Biological Variation Study of the EFLM Working Group on Biological Variation. Biological Variation Estimates Obtained from 91 Healthy Study Participants for 9 Enzymes in Serum. Clinical Chemistry. 2017. PMID 28428356. DOI 10.1373/clinchem.2016.269811.

    Laboratory method study · In 91 healthy adults sampled weekly for 10 weeks, within-subject variation of ALT was 9.3 percent and between-subject 28.2 percent, with sex-related differences.

  23. 23.

    Panteghini M. Supplementation of pyridoxal-5'-phosphate in aminotransferase reagents: a matter of patient safety. Clinical Chemistry and Laboratory Medicine. 2025. PMID 40788350. DOI 10.1515/cclm-2025-0947.

    Review · Omitting pyridoxal-5'-phosphate from aminotransferase reagents is the most frequent cause of biased results, yet only about one third of laboratories include it.

  24. 24.

    Nyblom H, Berggren U, Balldin J, Olsson R. High AST/ALT ratio may indicate advanced alcoholic liver disease rather than heavy drinking. Alcohol and Alcoholism. 2004. PMID 15208167. DOI 10.1093/alcalc/agh074.

    Cross-sectional study · AST/ALT ratio was 1.0 or less in 64 percent of 313 people in alcohol withdrawal, while 69 percent of 48 with alcohol-related cirrhosis had a ratio of 2 or more.

  25. 25.

    Aggarwal M, Garg R, Kumar P, et al.. Bi-directional Relationship Between Celiac Disease and Liver Chemistries: A Systematic Review and Meta-Analysis. Digestive Diseases and Sciences. 2023. PMID 36002677. DOI 10.1007/s10620-022-07663-w.

    Systematic review and meta-analysis · Raised liver enzymes in 18.7 percent of 4,265 adults at celiac diagnosis, normalizing on a gluten-free diet in 83.1 percent; biopsy-proven celiac disease in 4.5 percent of unexplained raised liver tests.

Related

Keep reading.

Reading a number well is the start of the work, not the end of it. If you would like a physician to read yours over time, Explore working with Dr. Tagge.