What Happens If You Fail a Pulmonary Function Test? | Retest

Seeing “fail” next to a breathing test can feel like a stamp on your health. In most clinics, it isn’t. Pulmonary function testing is a set of measurements that show how air moves in and out, how much air your lungs can hold, and how well oxygen moves into your blood.

“Failing” often means one or more numbers fell below the range expected for someone with your age and height. It can also mean the session didn’t meet quality rules, so the lab can’t trust the blow. In workplace or pre-op screening, “fail” may be a form label for “didn’t meet the cutoff,” yet a clinician still needs to read the pattern and your story.

How pulmonary function tests are judged

Pulmonary function tests (PFTs) can include spirometry, lung volumes, and diffusion testing. Not all visits include all three. Spirometry is the one most people know: you inhale fully, seal your lips on a mouthpiece, then blast the air out fast and keep going until you’re empty.

Your report compares your results with “predicted” values drawn from large reference data sets. Many labs show percent-predicted and a lower limit of normal (LLN). A value under the LLN is one common reason the report gets tagged abnormal.

In spirometry, these terms show up a lot:

• FEV1: air you force out in the first second.
• FVC: total air you force out during the blow.
• FEV1 / FVC: a ratio used to spot airway narrowing.

A low FEV1 / FVC ratio often points to obstruction. A low FVC with a normal or high ratio can point to restriction, air trapping, or a blow that ended early. Lung volumes add numbers like TLC (total lung capacity) and RV (residual volume). Diffusion adds DLCO, a gas-transfer check.

Quality is a big deal. Spirometry is repeated. Labs want several efforts that match. If the blows aren’t repeatable, the report may say “not acceptable” or “not repeatable,” and that can trigger a repeat visit.

Ask the technician if your session met acceptability and repeatability rules, and request a copy of the curve printout right then.

One thing that trips people up: “abnormal” on the printout doesn’t always mean “sick.” It means the value fell outside the lab’s reference range. That range is built from healthy volunteers, yet it still has a lower edge. If you sit near that edge, a small change in effort, posture, or medication timing can flip a flag on or off.

How the lab decides a blow is usable

Spirometry has rules for acceptability and repeatability. You’re asked to blow more than once so the lab can see the same result again. If one blow is big and the next is much smaller, the lab can’t tell which one reflects your true capacity, so the session may be marked low-quality.

That’s why technicians coach so hard. You may hear cues like “blast,” “keep going,” and “don’t stop.” You might do several tries, with short breaks in between, until the curves line up. If you get light-headed, ask for a pause. A brief rest often brings a cleaner second set of blows.

Failing a pulmonary function test for non-medical reasons

The test is picky too. Small technique issues can shave off speed or volume. The notes section matters as much as the headline number.

Test-day factors that drag numbers down

• Leaky seal at the mouthpiece or air escaping through the nose.
• Slow start where the blow ramps up instead of bursting out.
• Stopping early because you coughed, felt dizzy, or ran out of steam.
• Coughing in the first second, which can drop the FEV1.
• Medication timing, like using a rescue inhaler right before the test when you were told to hold it.
• Recent respiratory bug or allergy flare that tightened your airways.

Labs repeat the blow to chase a clean effort. The NIOSH spirometry quality assurance notes on common errors show how cough, hesitation, and early stop change curve shape and numbers.

Small practical details matter too. Tight clothing can limit your inhale. A height measurement that’s off can shift predicted values, which changes how the report labels the same raw number.

Pattern Seen On The Report	What It Often Points To	What Usually Comes Next
Low FEV1 / FVC ratio	Obstruction	Bronchodilator retest; history review
Low FVC with normal/high ratio	Restriction, air trapping, or short blow	Lung volumes to sort the pattern
Low TLC	Restriction	Imaging or other tests picked to match symptoms
High RV or high RV / TLC	Air trapping	Obstruction workup; med plan review
Low DLCO	Low gas transfer	Repeat DLCO if needed; imaging; heart-lung review
Big jump after bronchodilator	Reversible airway tightness	Talk through triggers and controller meds
“Not acceptable” / “not repeatable” note	Quality rules not met	Retest with extra time and coaching

What Happens If You Fail a Pulmonary Function Test?

A low result usually starts a workflow, not a one-line verdict. What happens next depends on why you took the test: symptoms, pre-op clearance, or a work screen.

Bring the printed report to your follow-up visit. Circle any notes about cough, early stop, or poor repeatability. If your height or weight seems off, ask the staff to remeasure. Those details can shift predicted values and sometimes change how a borderline result is labeled.

Step 1: The lab checks technique and repeats what it can

The technician may coach your start, adjust the nose clip, swap the mouthpiece, or ask for more blows. If you felt dizzy, had chest pain, or couldn’t keep going, that gets noted. If the lab couldn’t get repeatable curves, a retest appointment is common.

Step 2: You may do spirometry again after an inhaler

Many labs repeat spirometry after an inhaled bronchodilator. It’s a built-in check for reversible airway tightening. The Mayo Clinic’s spirometry page explains FEV1 and FVC and why clinicians use them to judge airflow limits.

Step 3: Your clinician reads the pattern with your story

PFT numbers need context: symptoms, exam, smoking history, exposures, and meds. A low ratio can fit asthma, COPD, or other airway problems. A low FVC can be a lung issue, a chest wall or muscle issue, or a technique issue. That’s why the “shape” of the curves and the tech notes matter.

Step 4: More tests may follow

Some people move to a full PFT visit with lung volumes and DLCO. Others get imaging, blood work, or an exercise walk test, based on symptoms and exam. The NHLBI overview of pulmonary function lab tests lists common options.

Follow-up tests you might be offered

If your report said “fail,” the next tests often answer one practical question: is this obstruction, restriction, low gas transfer, or a mix?

Lung volumes

Lung volumes can show whether a low FVC was due to restriction (low TLC) or air trapping (high RV). In many labs, this is done in a clear booth using body plethysmography.

Diffusion capacity (DLCO)

DLCO adds a gas-transfer check. Low values can show up with scarring, emphysema, blood-vessel issues, or anemia.

Challenge or exercise testing

If spirometry is normal but symptoms still sound like asthma, a clinician may order a challenge test. If shortness of breath shows up with exertion, an exercise test or walk test can sort breathing limits from conditioning, heart, or blood causes.

For a plain description of what PFTs measure, the American Thoracic Society patient page on pulmonary function tests is a solid starting point.

Before The Retest	What It Can Change	How To Handle It
Ask about inhaler holds	Can raise or lower FEV1 / FVC	Call the lab ahead so you don’t guess
Skip smoking or vaping	Can tighten airways and add cough	If you slip, tell the technician
Eat light before testing	Can help you inhale fully	Water is fine
Wear loose clothes	Less chest and belly restriction	Avoid tight waistbands
Arrive early	Rest can steady breathing	Give yourself a few minutes to settle
Bring a med list	Helps interpret changes	Include inhalers and recent steroids
Ask for a height recheck	Changes predicted values	Stand tall for measurement
Practice the seal	Leaks can lower volumes	Lips tight, tongue down

How a low result can change paperwork and plans

When PFTs are ordered for symptoms, a low result often changes the medical plan: more testing, new meds, or closer follow-up. When the test is tied to a job or clearance form, the impact can feel immediate.

Work programs may have written cutoffs for respirator use, firefighting, diving, or dusty jobs. If your value missed the program’s target, you might be pulled from that duty while the clinic repeats the test or requests a clinician review. Some people return after a better-quality retest. Others need a longer workup.

Questions to bring to the follow-up visit

• Which value was out of range: FEV1, FVC, the ratio, TLC, DLCO, or more than one?
• Did the lab note cough, early stop, leak, or poor repeatability?
• Was a bronchodilator retest done, and how much did the numbers change?
• What follow-up test will answer the main question for my case?
• What should I do with inhalers and meds before the next test?

When symptoms call for urgent care

PFTs can leave you light-headed for a moment. Still, sudden or severe breathing trouble isn’t something to wait out. Seek urgent medical care right away if you have chest pain, blue lips or face, fainting, coughing up blood, or breathing trouble that gets worse fast.

A “fail” result is a prompt to learn more, not a label you wear forever. With a clean retest and a clinician reading the pattern in context, you can usually get a clear next step and a plan that fits what’s going on.