How to Diagnose the Flu

Getting a Medical Diagnosis

Call your doctor if you think you have the flu. As soon as you notice flu symptoms, schedule an appointment with your doctor. Tell them as much as you can about your symptoms, including when they started and how severe they are. They may also want to know if you are taking any medications to manage your symptoms. Your doctor will likely do a physical exam to test your vital signs and check for flu symptoms. Since the flu is very contagious and potentially dangerous to high-risk individuals, your doctor’s office may request that you wear a mask over your nose and mouth while you’re around other patients in the waiting room. Also, carry hand sanitizer for when you are unable to wash your hands, such as after blowing your nose, sneezing or coughing, and do not throw tissues into a garbage can in the waiting room. If you can’t get an appointment with your regular doctor right away, visit an urgent care clinic as soon as possible.

Consent to a flu test if your doctor recommends it. To be sure that you have the flu, your doctor may perform a rapid influenza diagnostics test. This test involves swabbing the back of your nose or throat with a cotton swab. Results are usually available in about 15 minutes. The rapid influenza test is not definitive. It may tell you if you have the flu, but it will not tell you what type of flu you have. Your doctor may decide to treat you for a flu infection based on your symptoms even if you get a negative test result. If necessary, your doctor may refer you to a lab where more sensitive testing methods are available. This will tell your doctor the type of flu you have so they can prescribe the correct medication to treat it. If there’s a known flu outbreak in your area, you may not need to get tested if you notice symptoms like an abrupt fever, body aches, headache, dry cough, or extreme tiredness.

Follow your doctor’s care instructions carefully. If you test positive for the flu, or if your doctor suspects the flu based on your symptoms, they will likely recommend bed rest and plenty of fluids. They may suggest using over-the-counter medications such as Tylenol (acetaminophen) or Advil (ibuprofen) to manage your fever, aches, and pains. Your doctor may also prescribe an antiviral medication, but they are only helpful if administered within the first 3 days of symptoms appearing. The most common antiviral medications prescribed for the flu are oseltamivir (Tamiflu) and zanamivir (Relenza). Oseltamivir is oral, while zanamivir is taken through an inhaler. Follow up with your doctor if your symptoms do not improve after a few days or if they return or get worse.

Recognizing Flu Symptoms

Check for a sudden, high fever. If you abruptly develop a fever of 100.4 °F (38.0 °C) or above, you may have the flu. The fever may be accompanied by chills or sweating. Colds can also cause a fever, though they aren’t as common and tend to be slower. You may notice other mild cold symptoms, such as a headache and body aches, that develop over time rather than abruptly appearing like the flu.

Watch for tiredness, aches, and pains. The flu often causes pain or stiffness in the joints and muscles. You may feel these aches the most in your arms, shoulders, legs, and back. The flu can also cause severe headaches. With the flu, these aches and pains often start abruptly and tend to be much more severe than what you would expect from a cold.

Look for respiratory symptoms. The flu is a respiratory illness, so you may notice the effects in your lungs, nose, and throat. Check for symptoms such as nasal congestion, a dry cough, and a sore throat. The cough that accompanies the flu is typically more severe than the cough that comes with a cold. A cough from a cold will also produce watery, clear sputum, while a cough from the flu will produce thick yellow or green sputum. While the flu may cause nasal congestion, you’re less likely to get the kind of persistent watery discharge that you’d get with a cold.

Make note of fatigue and weakness. The flu will often make you feel completely exhausted. You may find it difficult to get out of bed or concentrate on simple tasks. Your muscles may also feel weak or shaky. Fatigue is typically one of the longest-lasting symptoms of the flu. You may continue to feel tired and weak for 2 or more weeks after your symptoms began.

Pay attention to vomiting or diarrhea. While influenza is not the same thing as a “stomach flu,” it can sometimes cause gastrointestinal symptoms. If you have nausea, vomiting, or diarrhea along with other flu symptoms (such as a fever, aches, and a cough), you may have the flu. Vomiting and diarrhea with the flu are more common in children, but adults may sometimes experience these symptoms as well. However, children, especially young children, will experience complications from these side effects faster than adults.

Get medical attention right away for severe symptoms. The flu can sometimes cause serious complications, including pneumonia and other secondary infections. Children under 5, adults over 65, people with chronic illnesses, and pregnant women are particularly at risk. Get emergency medical care if you see symptoms such as: Labored or rapid breathing Confusion or extreme lethargy Feelings of pain or pressure in the chest or abdomen A fever accompanied by a skin rash Flu symptoms that improve and then return or get worse, especially a cough or fever