Fractional Exhaled Nitric Oxide
FeNO Test
Measure airway inflammation with a simple non-invasive breath test. FeNO helps diagnose asthma, predict treatment response, and monitor disease control with precision.
What is a FeNO test?
FeNO (Fractional Exhaled Nitric Oxide) is a quick, non-invasive breath test that measures the level of nitric oxide in your exhaled breath. Nitric oxide is produced by inflamed airways, particularly when eosinophilic (allergic-type) inflammation is present.
The test takes just a few minutes. You breathe in deeply, then exhale slowly and steadily into the device. The analyzer measures nitric oxide levels in parts per billion (ppb), providing immediate results.
Why FeNO is a valuable biomarker
FeNO directly reflects airway inflammation, making it more specific for allergic asthma than symptoms or spirometry alone. It helps predict who will respond to inhaled corticosteroids and can detect inflammation even when lung function appears normal.
2-5 minutes
Total test time
Immediate results
Doctor-friendly reports
Non-invasive
No needles or discomfort
Who should consider a FeNO test?
Individuals with persistent cough, wheezing, or breathlessness
Individuals with asthma symptoms or poorly controlled asthma
Individuals on inhalers for asthma monitoring
Post-COVID patients with lingering respiratory symptoms
Children with recurrent wheezing or cough
Individuals living in polluted cities
Why the FeNO test matters even more in polluted cities
Living in cities with high levels of air pollution exposes your lungs to toxins almost every day, even when you can't see or smell it. The FeNO test acts like a smoke alarm for your lungs and helps detect hidden airway inflammation caused by pollution, dust, smoke, and allergens.
"Are my lungs silently suffering?" — FeNO helps answer this early.
What happens in a FeNO test?
Sit comfortably
Attach the mouthpiece and relax.
Inhale deeply
Breathe in through the mouthpiece to full capacity.
Slow exhalation
Exhale slowly and steadily into the device for 6-10 seconds.
Immediate analysis
The device measures nitric oxide levels instantly.
Reassurance
Safe & non-invasive
No needles or discomfort
Quick & simple
Completes in 2-5 minutes
Doctor-friendly reports
Clear, actionable insights
How FeNO helps in asthma management
Confirm diagnosis
High FeNO supports asthma diagnosis when symptoms and spirometry are inconclusive.
Predict response
High FeNO predicts good response to inhaled corticosteroids.
Monitor control
Track inflammation levels to optimize treatment and prevent flare-ups.
Understanding your FeNO results
FeNO ranges differ for adults and children. Your doctor will interpret these values in clinical context.
FeNO range for adults
< 25 ppb
Normal
Airway inflammation is low; asthma/allergy less likely.
25 - 50 ppb
Intermediate
Mild inflammation; may need monitoring or medication adjustment.
> 50 ppb
High
Significant airway inflammation; indicates active asthma/allergy.
FeNO range for children
< 20 ppb
Normal
Airway inflammation is low; asthma/allergy less likely.
20 - 35 ppb
Intermediate
Mild inflammation; may need monitoring or medication adjustment.
> 35 ppb
High inflammation
Significant airway inflammation; indicates active asthma/allergy.
How doctors use your FeNO results?
Regular FeNO monitoring provides objective data about your airway inflammation status, not just symptoms. This helps your doctor:
Adjust medication doses based on inflammation, not just symptoms
Identify loss of disease control before symptoms worsen
Safely step down therapy when inflammation is controlled
Assess treatment adherence objectively
Frequently asked questions
Is the FeNO test painful?
No. Most patients find it easier than expected.
How should I prepare for the FeNO test?
Avoid nitrate-rich foods and caffeine; follow inhaler instructions as advised.
How long does the FeNO test take?
Usually 2–5 minutes for the breathing measurement.
Can children take the FeNO test?
Yes. We use child-friendly devices for accurate measurement.
How often should I repeat the FeNO test?
Depends on your doctor’s guidance and symptom monitoring.
Does FeNO replace other lung tests?
No. It complements PFT, spirometry, and other tests by showing inflammation levels.
Why choose Aelira health for FeNO test
Lung Specialists
Expert interpretation of inflammation
Gold Standard Devices
Precise nitric oxide measurement
Instant Results
Immediate reports for asthma control
Patient-First Approach
Unbiased, diagnostic-focused care
Ready to book your FeNO test?
Get detailed insights into your lung health in our calm relaxing setting at our dedicated lung health centrein south delhi