Your doctor will do a physical exam to determine if you have asthma. This will involve checking your eyes, ears, throat, nose, chest, lungs, and skin. They will examine your breathing to see how you exhale breath from your lungs. In some instances, they may do a lung function test which involves watching your breathing before and after you inhale a medication known as a bronchodilator. It is common for doctors to prescribe an inhaler as a trial medicine to see if it improves your breathing.