Methacholine test: preparation and procedure.

What the test shows.

The methacholine test measures how easily your airways narrow. A negative result speaks strongly against current asthma.

How to prepare.

• Important information about your medication: only pause if the clinic has asked you to. If the clinic has given you instructions, follow them, and call if you are in doubt.
• Medication pause (the clinic's standard): short-acting reliever (e.g. salbutamol): 8 hours · long-acting beta2 agonist (e.g. formoterol, salmeterol): 36–48 hours · ultra-long-acting beta2 agonist (e.g. vilanterol, indacaterol): 48 hours · ipratropium (e.g. Atrovent): 12 hours · long-acting anticholinergic (e.g. tiotropium): 7 days · antihistamine (allergy medication): 3 days · inhaled corticosteroid and montelukast: as agreed with the clinic.
• Avoid strenuous exercise and smoking/nicotine in the last hour, and a large meal in the last 2 hours. Coffee and tea make no difference before a methacholine test.
• An airway infection within the last 2–4 weeks: please call and move the appointment.

Duration

The test itself takes about 30–45 minutes (up to five steps 3 minutes apart, plus spirometry before and after). Expect up to two hours at the clinic in total.

How it is done.

First, spirometry. You then inhale methacholine in small, increasing amounts through a mouthpiece, and your lung function is measured after each step. The test stops when your lung function has fallen by 20 per cent, or when the last step has been given. The staff are with you the whole time.

After the test

If the test is positive, or if you feel tightness in your chest or cough, you are given airway-opening medication, and your lung function is measured again after 10 minutes, so it is back at the starting point before you leave. If the test is negative and you feel well, you are not given medication, but you can have it if you need it.

Side effects

Brief coughing, chest tightness, wheezing or a slight headache; it fades quickly, especially after the medication.

When the test cannot be done.

The test cannot be done with severely reduced lung function, a heart attack or stroke within the last 3 months, uncontrolled high blood pressure or a known aneurysm (a bulge on an artery). If you are pregnant or breastfeeding, tell us in advance. Also tell us if you take medication for dementia or myasthenia (a cholinesterase inhibitor).

Your result

The result is available straight after the test and is reviewed with you before you leave.

What to bring

• Bring ID, for example your health insurance card or driving licence (app versions also count) or your passport. Your CPR number alone is no longer enough.
• Bring an up-to-date medication list and any earlier lung function measurements.
• Always bring your reliever inhaler.
• Arrive in good time, so you are not out of breath when we start.

Background and sources

• The clinic's own source for medication pauses and preparation (version 20-10-2026) and the clinic's test protocols.
• Coates AL et al. ERS technical standard on bronchial challenge testing: general considerations and performance of methacholine challenge tests. Eur Respir J 2017;49:1601526.

Asthma testing