What Is the Normal Range for an Alpha-1 Antitrypsin Test?

Alpha-1 antitrypsin (AAT) is a protein your liver makes, and its main job is to protect your lungs from damage by the body’s own enzymes.1PubMed. Alpha-1 antitrypsin deficiency: pathogenesis, clinical presentation, diagnosis, and treatment A blood test for it measures how much of that protection you have circulating. For most adult labs, a normal level falls roughly between 100 and 220 mg/dL (about 20 to 53 µmol/L), though the exact range printed on your report depends on the lab. The number doctors watch most closely is a much lower line, about 57 mg/dL (11 µmol/L), where lung risk rises. Because infection and inflammation can push the level up temporarily, a normal result doesn’t always rule out a deficiency.

Normal Alpha-1 Antitrypsin Levels in Adults

You may see any of these ranges on a report or in the medical literature:

The edges shift because labs use different equipment and different healthy groups to set their ranges. Compare your number with the range printed beside it on your own report.

The two units on your report express the same amount of protein in different ways. One counts the weight of AAT in a set amount of blood, while the other counts the number of AAT molecules, so its numbers look much smaller. To roughly convert, divide the mg/dL figure by about 5.2 to get µmol/L. Some reports use g/L instead, and 1 g/L equals 100 mg/dL. Comparing a µmol/L result with an mg/dL range can make a normal result look alarmingly low, so match the unit to the range.

A result just outside the range is usually less dramatic than it sounds. A number slightly above the top is not a concern on its own. One slightly below the bottom is common in people who carry one altered gene. The lab may flag either as abnormal even when your doctor isn’t worried. A flagged result near the edge is a prompt to ask your doctor, not a diagnosis.

The test shows how much AAT is circulating on the day of the draw. It doesn’t show how well your lungs or liver are working, and it doesn’t tell you which gene type you have, which is why a level is often only the first step.

What a Low Level Means for Your Lungs and Liver

Doctors treat a blood level of 11 µmol/L, about 57 mg/dL, as the protective threshold.6PubMed. Alpha-1 antitrypsin deficiency: clarifying the role of the putative protective threshold Below it, the risk of emphysema, a lung disease that destroys the air sacs, is believed to rise.7PubMed. A review of α1-antitrypsin deficiency This cutoff is a long-accepted working estimate rather than a sharp line, and researchers are still refining it.8PubMed. Alpha-1 antitrypsin deficiency: clarifying the role of the putative protective threshold Risk climbs gradually as the level falls further below the line, and smoking or exposure to dust and fumes changes how much a low level matters in a given person. That’s why doctors read your level together with your gene type, symptoms, and breathing tests.

Alpha-1 antitrypsin deficiency (Alpha-1, AATD) is an inherited condition, and its typical lung effect is COPD and emphysema.9PubMed. Alpha-1 antitrypsin deficiency: pathogenesis, clinical presentation, diagnosis, and treatment Severe COPD can begin in young adulthood, earlier than in most people with COPD.10PubMed. Alpha-1 antitrypsin deficiency: pathogenesis, clinical presentation, diagnosis, and treatment Emphysema is rarely detectable before about age 20.11PubMed Central. Alpha-1-Antitrypsin Deficiency: An Important Cause of Pediatric Liver Disease Warning signs include shortness of breath on exertion that starts in your 30s or 40s, and a wheeze or cough that doesn’t improve like ordinary asthma.

The liver can be harmed too. In the common Z form, the protein clumps inside liver cells instead of leaving them, which is why blood levels are low.12PubMed. A review of α1-antitrypsin deficiency The trapped clumps can scar the liver, and more clumping goes with more scarring and worse outcomes.13PubMed Central. The Alpha-1 Antitrypsin Polymer Load Correlates With Hepatocyte Senescence, Fibrosis Stage and Liver-Related Mortality Liver disease can show up at any age, even 1 to 2 months after birth.14PubMed Central. Alpha-1-Antitrypsin Deficiency: An Important Cause of Pediatric Liver Disease Between 4 and 10 percent of children with the deficiency develop significant liver disease by age 20, making it the most common genetic cause of childhood liver disease.15PubMed Central. Alpha-1-Antitrypsin Deficiency: An Important Cause of Pediatric Liver Disease Signs to watch for are yellowing of the skin or eyes, abnormal liver tests without another cause, and in babies, jaundice that lasts after birth.

The lungs and liver suffer in different ways. In the lungs, too little protein gets out into the blood to guard against damaging enzymes. In the liver, the misfolded protein piles up inside the cells that make it. So lung risk follows the blood level, while liver risk follows the gene type, and some people have lung trouble without liver trouble or the reverse. Many people with Alpha-1 deficiency never develop significant liver disease.

A low level means less protection, not that damage has already happened. Breathing tests and sometimes scans show whether there is actual lung damage, while liver blood tests or imaging check the liver separately.

Typical Levels by Gene Type

Everyone inherits two copies of the AAT gene, one from each parent, and M is the normal version. Z and S are the most common altered versions, and more than 120 versions have been identified.16PubMed. Lessons from the Past: Some Histories of Alpha-1 Antitrypsin Deficiency Before Its Discovery Your combination is your gene type (the phenotype or genotype), written as two letters. Typical blood levels run like this:

The ranges overlap. An MZ result at the top of its range can sit inside the MM range, so a level alone can’t always tell a carrier from someone with normal genes. That overlap is why genetic testing is often added. ZZ is the type with the clearest treatment guidance.

Most MZ carriers have levels above the protective line. Smoking still adds lung risk for carriers, and you can pass Z to your children, so a partner’s test matters for family planning.

Some rare “null” versions make almost no AAT, so the protein may be undetectable in the blood.21PubMed Central. Variants of SERPINA1 and the increasing complexity of testing for alpha-1 antitrypsin deficiency People with these versions are at high risk of emphysema, often with symptoms around age 38.22American Journal of Respiratory and Critical Care Medicine. B44-10 Null SERPINA1 Alleles: A Comparative Study of Rare Forms of Alpha-1 Antitrypsin Deficiency in Ireland Null versions don’t damage the liver, because no protein builds up in liver cells.23PubMed Central. Variants of SERPINA1 and the increasing complexity of testing for alpha-1 antitrypsin deficiency Other rare versions can cause lung or liver disease even with levels that look less extreme.24PubMed Central. Variants of SERPINA1 and the increasing complexity of testing for alpha-1 antitrypsin deficiency

Why a Normal Result Can Be Misleading

AAT levels go up with infection, inflammation, injury, and higher estrogen levels.25PubMed. The Effects of Inflammation on Alpha 1 Antitrypsin Levels in a National Screening Cohort AAT rises because the liver makes more of it when the body is under stress. The boost is short-lived and fades once the illness settles. Even people with a true deficiency may test normal or high during an acute infection.26Blood Sciences Department of Clinical Biochemistry. Alpha-1 antitrypsin fact sheet for primary care The rise appeared across every gene type when C-reactive protein (CRP), a blood marker of inflammation, was 5 mg/L or higher.27PubMed. The Effects of Inflammation on Alpha 1 Antitrypsin Levels in a National Screening Cohort Some labs therefore check CRP alongside AAT to see whether inflammation may be raising the result.

Estrogen works the same way. Pregnancy or estrogen-containing medicines can nudge AAT upward, so a borderline normal result may overstate your true baseline. Mention these to whoever reviews your result.

A level alone also misses some at-risk people. Using 85 mg/dL as a cutoff catches about 99.5% of people with ZZ.28PubMed. α1-Antitrypsin phenotypes and associated serum protein concentrations in a large clinical population But the same cutoff misses about 1 in 7 people who carry two altered genes of other kinds.29PubMed. α1-Antitrypsin phenotypes and associated serum protein concentrations in a large clinical population

A repeat or genetic test is worth asking about if you were sick, recently injured, pregnant, or taking estrogen when tested. It also makes sense if your level is low-normal but you have early COPD or unexplained liver disease, or if a relative has a confirmed altered gene. Ask whether your CRP was checked at the same time.

Tests That Follow an Abnormal Result

The level test is usually done by a standard automated blood method that measures the amount of protein.30PubMed Central. Methodologies for the Determination of Blood Alpha1 Antitrypsin Levels: A Systematic Review A second test then identifies which form of the protein you make, which shows your gene type.31PubMed. Isoelectric focusing phenotyping and denaturing gradient gel electrophoresis genotyping: a comparison of two methods in detection of alpha-1-antitrypsin variants A DNA test of the AAT gene, called SERPINA1 on reports, can find rarer versions.32PubMed. Alpha-1-Antitrypsin Deficiency Targeted Testing and Augmentation Therapy: A Canadian Thoracic Society Meta-Analysis and Clinical Practice Guideline If the level and the gene result don’t match, labs may run a further protein-type test to sort it out.33PubMed. Diagnosis of alpha-1-antitrypsin deficiency: An algorithm of quantification, genotyping, and phenotyping

Which test comes first depends on how strong the suspicion is. Canadian guidance suggests going straight to DNA testing when suspicion is high.34PubMed. Alpha-1-Antitrypsin Deficiency Targeted Testing and Augmentation Therapy: A Canadian Thoracic Society Meta-Analysis and Clinical Practice Guideline With moderate suspicion, it suggests a level test first and DNA testing if the level is below 23 µmol/L, about 120 mg/dL.35PubMed. Alpha-1-Antitrypsin Deficiency Targeted Testing and Augmentation Therapy: A Canadian Thoracic Society Meta-Analysis and Clinical Practice Guideline That follow-up line sits inside the normal range on many reports, so a normal-looking number can still lead to more testing.

All of these are ordinary blood draws, sometimes a finger-prick blood spot, and fasting is usually not needed. Gene results can take days to weeks, and they may come with an offer of genetic counseling.

Who Should Be Tested

Guidelines recommend testing every person with COPD at least once, regardless of age, ethnicity, or severity.36PubMed Central. Recommendations for the diagnosis and treatment of alpha-1 antitrypsin deficiency Testing is also advised for emphysema and for asthma that leaves airways persistently narrowed.37PubMed Central. Recommendations for the diagnosis and treatment of alpha-1 antitrypsin deficiency Unexplained chronic liver disease and unexplained bronchiectasis, a type of lasting airway widening, are also reasons to test.38Chronic Obstructive Pulmonary Diseases:Journal of the COPD Foundation. The Diagnosis and Management of Alpha-1 Antitrypsin Deficiency in the Adult So is a rare painful skin condition, panniculitis, with tender red lumps from breakdown of fat under the skin, which can be caused by the deficiency.39Alpha-1 Foundation. Alpha-1 and Panniculitis People with severe forms of panniculitis are advised to be tested.40Chronic Obstructive Pulmonary Diseases:Journal of the COPD Foundation. The Diagnosis and Management of Alpha-1 Antitrypsin Deficiency in the Adult

Alpha-1 deficiency looks like ordinary COPD, so symptoms alone cannot separate the two. Gene type does not change during your life, so once it has been confirmed it doesn’t need to be retested.

Asthma is on the list because some people labeled as having asthma actually have airway damage that does not fully reverse. If your breathing remains narrowed despite good treatment, testing is reasonable. Ordinary asthma that responds well to treatment does not call for testing on that basis alone.

Adult siblings of anyone with an altered AAT gene should be offered genetic counseling and testing.41Chronic Obstructive Pulmonary Diseases:Journal of the COPD Foundation. The Diagnosis and Management of Alpha-1 Antitrypsin Deficiency in the Adult Parents, children, and wider family can be offered the same.42Chronic Obstructive Pulmonary Diseases:Journal of the COPD Foundation. The Diagnosis and Management of Alpha-1 Antitrypsin Deficiency in the Adult Testing whole populations isn’t considered worth the cost, but testing people with COPD is.43PubMed. Cost-effectiveness of population screening for alpha-1 antitrypsin deficiency: a decision analysis

To ask for the test, mention your COPD or symptoms and ask whether you’ve had an AAT level. If a relative was diagnosed, bring their gene type if you know it, and ask whether a level, a gene test, or both makes sense.

What You Can Do If Your Level Is Low

Smoking changes the outlook more than anything else. In people with the deficiency and emphysema, breathlessness began around age 32 in smokers versus 51 in non-smokers.44PubMed. Smoking, lung function, and alpha 1-antitrypsin deficiency Average age at death from lung causes was 48 in smokers and 67 in non-smokers.45PubMed. Smoking, lung function, and alpha 1-antitrypsin deficiency Smokers lost lung function about four times faster than non-smokers.46PubMed. Smoking, lung function, and alpha 1-antitrypsin deficiency Quitting and avoiding secondhand smoke is the single most useful step.

Quitting helps even after a diagnosis. Lung function often declines more slowly after quitting, even when damage has already occurred. Doctors can offer counseling and medicines to make quitting more achievable.

Augmentation therapy, regular IV infusions of AAT from donated blood (called AAT infusions from here on), is offered to adults who don’t smoke.47PubMed Central. Diagnosis and augmentation therapy for alpha-1 antitrypsin deficiency: current knowledge and future potential It is meant for people with a severe deficiency gene, a level below 11 µmol/L, and reduced lung function on breathing tests.48PubMed Central. Diagnosis and augmentation therapy for alpha-1 antitrypsin deficiency: current knowledge and future potential It is added to, not used instead of, usual COPD treatment.49Canadian Journal of Respiratory, Critical Care, and Sleep Medicine. Alpha-1-antitrypsin deficiency targeted testing and augmentation therapy: A Canadian Thoracic Society meta-analysis and clinical practice guideline

Everyday habits matter too. Avoid dust, fumes, and smoke at work where possible, and stay current on flu and pneumonia vaccines, since infections strain the lungs. Limit alcohol to protect the liver, and get regular breathing tests and liver checks to track changes.

At your next appointment, you might ask:

  • What is my gene type, not just my level?
  • Do I meet the criteria for AAT infusions?
  • How often should my lungs and liver be checked?
  • Should my children or siblings be tested?