Symptoms of Influenza

Flu symptoms can vary from person to person but most people with influenza will experience some, if not all, of the symptoms listed here. If you are concerned and think you might have the flu, contact your health care provider to determine the best course of action and treatment for you.

Frequent Symptoms

Symptoms of the flu are similar to those experienced when you have a cold or upper respiratory infection. The main difference is influenza symptoms come on rapidly. People typically go from feeling fine to miserable in a matter of hours. Here's a closer look at common symptoms.

Fever and Chills

Fever is almost always present with the flu, and it usually comes on suddenly. When you have a high fever, you're also likely to experience chills. The higher your body temperature, the colder the air will feel.

This is why you feel cold when you have a fever and why you want to cover up with blankets to get warm. Unfortunately, if you bundle up when you have a fever, you can actually increase your body temperature, which won't help you feel any better.

It's hard to get comfortable when you have a fever. You can use appropriate fever-reducing medications.

Exhaustion

One of the most significant symptoms that people describe when they get the flu is pure exhaustion. This is generally an overall feeling of being completely worn out. You probably will be unable to perform daily activities. It's so severe that it is hard to get out of bed. This exhaustion is much more pronounced than the tiredness you may feel from a cold.

Aches and Pains

One of the most common descriptions people give when they have the flu is "achy." Your muscles are usually very sore and moving around too much causes discomfort. Body aches and pains are more common with the flu than with many other illnesses.

Coughing

Coughing may be productive (producing mucus) or non-productive. With the flu people most often suffer from a dry cough.

If you develop a productive cough with fever, contact your doctor. This is especially true if you have had a dry cough, start to feel better, then have a wet or productive cough with a fever. This is often how a secondary infection, like pneumonia, develops.

Congestion

Severe congestion is more common when you have a cold but many people will experience some congestion with the flu as well. It is typically mild.

Headache

Headaches are common with the flu and can be quite severe. Like the rest of your body, the head will ache when you have the flu.

Throbbing head pain can make you miserable when you already feel bad with the flu. Taking an OTC pain reliever like acetaminophen or ibuprofen may help.

Rare Symptoms

Vomiting and Diarrhea

Vomiting and diarrhea are not common flu symptoms for most people. However, some people do experience these symptoms with the actual flu.

Children are more likely to have vomiting and diarrhea with influenza, but they may occur occasionally in adults as well. About 10% of children have these symptoms with the flu. 

If vomiting and diarrhea are your primary and most significant symptoms, you probably have a stomach bug (sometimes referred to as the stomach flu), not influenza.

Complications

For most people, flu symptoms resolve in one to two weeks. However, some people are at higher risk of complications, which may be life-threatening. In fact, there are 20,000 to 60,000 deaths from influenza in the United States each year.

Those at higher risk of complications from the flu include:

  • Adults ages 65 and older
  • Pregnant women
  • Children under the age of 5
  • People with chronic medical conditions such as asthma, diabetes, and heart disease

Complications from the flu range from mild sinus or ear infections to serious and life-threatening. Serious complications include: 

  • Pneumonia
  • Myocarditis, inflammation of the heart
  • Encephalitis, swelling of the brain
  • Multi-organ failure
  • Sepsis
  • Worsening of chronic medical conditions

When to See a Doctor

If based on the symptoms, you believe you may have your flu, call your doctor right away. Antiviral medications, such as Tamiflu, can lessen the severity and duration of the flu if started within the first 48 hours of symptom onset.

Your doctor may want you to come in to confirm the influenza virus with a rapid in-office test or may prescribe solely based on your symptoms and flu activity in your area.

You should also contact your doctor if symptoms continue to worsen after a week with the flu or if once you start to feel better develop a fever or productive cough as influenza can turn into secondary infections, such as bronchitis and pneumonia.

When to call 9-1-1

The flu can quickly take a turn for the worse if you experience these symptoms, seek immediate medical care:

  • Difficulty breathing or shortness of breath
  • Persistent pain or pressure in the chest or abdomen
  • Persistent dizziness, confusion, inability to arouse
  • Seizures
  • Not urinating
  • Severe muscle pain
  • Severe weakness or unsteadiness
  • Fever or cough that improves but then returns or worsen
  • Worsening of chronic medical conditions

In children, seek immediate medical attention for these symptoms:

  • Fast breathing or trouble breathing
  • Bluish lips or face
  • Ribs pulling in with each breath
  • Chest pain
  • Severe muscle pain (child refuses to walk)
  • Dehydration (no urine for 8 hours, dry mouth, no tears when crying)
  • Not alert or interacting when awake
  • Seizures
  • Fever above 104°F
  • In children less than 12 weeks, any fever
  • Fever or cough that improve but then return or worsen
  • Worsening of chronic medical conditions
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Article Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. Centers for Disease Control and Protection. Flu Symptoms & Complications.

  2. U.S. Centers for Disease Control and Prevention. Disease Burden of Influenza.

  3. U.S. Centers for Disease Control and Prevention. People at High Risk for Flu Complications.