What a spirometry test does

A spirometry test measures how much air your lungs can hold and how fast you can breathe air in and out. You blow into a tube connected to a machine called a spirometer, which records the numbers. The test takes about 15 minutes and is painless, though it requires you to follow specific breathing instructions.

Doctors order spirometry when they suspect a lung problem — chronic obstructive pulmonary disease (COPD), asthma, or restrictive lung disease — or to track how well a known condition is responding to treatment. The numbers tell your doctor whether your airways are narrowed, whether your lungs are stiff, or whether your breathing muscles are weak.

Spirometry is one of the most common lung tests in primary care offices and pulmonology clinics. It costs between $100 and $300 out of pocket without insurance, though Medicare and most commercial plans cover it when a doctor orders it for a medical reason.

Key Takeaways

  • Spirometry measures lung capacity and airflow by having you blow forcefully into a tube, and the machine records how much air moves and how fast.
  • Your doctor uses the results to diagnose or monitor COPD, asthma, and other lung diseases, or to check how well your lungs work before surgery.
  • You should not smoke, use inhalers, or do strenuous exercise for at least an hour before the test, and you need to follow the technician's breathing instructions exactly.
  • The test produces two main numbers: FEV1 (how much air you exhale in one second) and FVC (total air you can exhale), which your doctor compares to normal ranges for your age, height, and sex.

Why doctors order spirometry

Spirometry is ordered when you have symptoms that suggest a lung problem — shortness of breath, chronic cough, wheezing, or chest tightness — and your doctor needs to measure whether your lungs are actually working poorly or whether something else is causing the symptoms.

It is also used to screen people at high risk: smokers or former smokers, people with a family history of COPD, workers exposed to dust or chemicals, and people over 40 with a significant smoking history. Some doctors order it before major surgery to make sure your lungs can handle anesthesia.

If you already have a diagnosis like COPD or asthma, your doctor may order spirometry every year or two to see whether the disease is getting worse or whether your medications are working. A drop in your numbers from one test to the next tells your doctor to adjust your treatment.

How to prepare and what to expect

Do not smoke, use inhalers (including rescue inhalers), or do strenuous exercise for at least one hour before your test. Eat a light meal beforehand — a full stomach can make it harder to take a deep breath, and low blood sugar can make you dizzy. Wear loose, comfortable clothing that does not restrict your chest.

When you arrive, the technician will explain the test and may ask about your medical history, current medications, and whether you have had spirometry before. They will fit a soft clip on your nose to close your nostrils so all air goes through your mouth into the tube.

The technician will give you specific instructions: breathe normally a few times, then take the deepest breath you can, then blow out as hard and as fast as you can for at least six seconds. You will do this three to eight times. It is normal to feel lightheaded or tired afterward — you have just worked your lungs hard.

Understanding your spirometry results

The two main numbers are FEV1 (forced expiratory volume in one second — how much air you can blow out in the first second) and FVC (forced vital capacity — the total amount of air you can blow out after taking the deepest breath). Your doctor also looks at the FEV1/FVC ratio, which is FEV1 divided by FVC.

Your results are compared to predicted values based on your age, height, sex, and race. If your FEV1 is 80% or higher of the predicted value, your lungs are considered normal. If it is 50 to 79%, you have mild to moderate airflow obstruction. Below 50% means severe obstruction.

A low FEV1/FVC ratio (below 70%) suggests your airways are narrowed, which points to obstructive disease like COPD or asthma. A low FVC with a normal ratio suggests your lungs are stiff or small, which points to restrictive disease. Your doctor will explain what your specific numbers mean for your diagnosis and treatment.

When spirometry is not reliable

Spirometry depends on your effort and cooperation. If you do not blow hard enough or long enough, the numbers will be falsely low and your doctor may think your lungs are worse than they are. The technician will ask you to repeat the test if your efforts do not look good on the screen.

The test is also less reliable if you have severe arthritis or muscle weakness that makes it hard to take a deep breath or blow forcefully. If you are very short of breath or having chest pain on the day of the test, tell your doctor — they may reschedule.

Certain medications can affect results: some asthma and COPD drugs should be stopped before testing (your doctor will tell you which ones and for how long), and stimulants like caffeine or decongestants can raise your heart rate and make you feel shaky during the test.

Other lung tests that may follow spirometry

If spirometry shows obstruction, your doctor may order a bronchodilator test, in which you use a rescue inhaler and then repeat spirometry to see whether your airways open up. This helps distinguish asthma (which usually improves with the inhaler) from COPD (which usually does not).

A diffusion test measures how well oxygen moves from your lungs into your blood and is often done alongside spirometry if restrictive disease is suspected. A lung volume test measures the total amount of air your lungs can hold, which spirometry alone cannot do.

If your spirometry is normal but your symptoms persist, your doctor may order a methacholine challenge test, in which you inhale a substance that makes airways tighten if you have asthma, or imaging like a chest X-ray or CT scan to look for other causes.

Cost and insurance coverage

Medicare covers spirometry when ordered by a doctor for a medical reason, with no copay if your doctor accepts assignment. Most commercial insurance plans also cover it, though you may have a copay or coinsurance. Without insurance, the test typically costs $100 to $300 depending on the clinic.

Some urgent care clinics and community health centers offer spirometry at a lower cost or on a sliding fee scale based on income. If cost is a concern, ask your doctor's office whether they can refer you to a lower-cost option or whether the test can wait until your insurance situation changes.

Frequently Asked Questions

Can I use my rescue inhaler before a spirometry test?

No. Stop using rescue inhalers at least one hour before the test, and stop long-acting inhalers the night before if your doctor tells you to. Using an inhaler before the test can open your airways artificially and give a falsely high reading. Your doctor will tell you exactly which medications to hold and for how long.

What if I cannot blow hard enough because of pain or weakness?

Tell the technician before the test starts. They may be able to adjust the procedure or reschedule when you are feeling better. If you have chronic pain or muscle weakness, your doctor may order a different type of lung test that does not require forceful breathing.

How often do I need spirometry if I have COPD?

Most doctors order it once a year to track whether your lung function is stable or declining. If your symptoms are getting worse or your doctor changes your medications, they may order it sooner. If your numbers are stable year after year, your doctor may space tests further apart.

Does spirometry hurt?

No, it is painless. You may feel tired or lightheaded after blowing hard several times, and your chest or throat may feel slightly sore from the effort, but these feelings pass quickly. If you feel chest pain during the test, stop and tell the technician when ready.

Can I eat or drink before spirometry?

Eat a light meal if you are hungry, but avoid a large meal that fills your stomach — it makes it harder to take a deep breath. Drink water normally. Avoid caffeine and stimulants for a few hours before the test, as they can make your heart race and affect how you feel during the procedure.