Nocturnal asthma can significantly disrupt nighttime sleep which results in a decreased ability to function throughout the day, it becomes prominent to identify the specific causes and find the best possible treatment. The easiest way to diagnose nocturnal asthma is to check a bedtime peak flow and peak flow rate on awakening. It the difference comes out to be more than 15%, the symptoms may have caused the nocturnal variability.

The doctor would start up with the lung test, ear, and nose and then he would ask you a couple of questions related to the problems you face in the nighttime. He would enquire you of the nasal problem, sinus, cough, wheezing, shortening of breath, chest tightness, chest pain etc, if you encounter them during your nighttime sleep. He would then ask you about the cooling level of the air conditioners of your bedroom or the presence of any other asthma triggers present in your room.

The chances to diagnose nocturnal asthma are intensified if you have persistent coughing or if you have a history of smoking behind you. This is because the lung function is largely reduced. There are portable meters to measure the air flow rate through the airways. Taking measurement of airflow out of the lungs in the evening and morning can help in testing the nocturnal asthma.