A sinus infection can be difficult to diagnose in the early stages because it can mimic a common cold. Both can cause nasal congestion and fatigue. However, a common cold usually will improve in five to seven days, while an untreated sinus infection can last three weeks or longer. Sinus infections also are more likely to cause a green nasal discharge, fever and facial pain.
Your doctor will diagnose acute sinusitis based on your symptoms, medical history and a simple office examination. The doctor will ask about your symptoms and how long they last, look into your ears, nose and throat, and may tap or press on your face to test for tenderness over specific sinuses.
If your doctor is uncertain of your diagnosis, he or she may use other methods to see inside the sinuses. Some physicians may insert a nasopharyngoscope (a thin, lighted tube with a camera on the end) into your nose to look for abnormalities. X-rays and computed tomography scans (CT) also can provide a look at the sinuses, especially those that are deep within the head.