Symptoms of the Flu

In This Article

Flu symptoms can vary from person to person, but most people with influenza will experience some degree of fever, chills, headaches, body aches, congestion, coughing, and fatigue.

While the symptoms are similar to a cold or upper respiratory tract infection, the main difference is that flu symptoms hit you quickly. With the flu, you typically go from feeling fine to miserable in a matter of hours.

If you think you might have the flu, contact your healthcare provider to determine the best course of action and treatment for you. Anti-viral medications taken in the first 48 hours after symptom onset can reduce the severity and duration of flu symptoms.

Frequent Symptoms

Flu symptoms come on quickly and typically last a week or two, though sometimes symptoms can linger mildly for a bit before you feel back to normal. Common symptoms include the following.

Flu Symptoms
 Verywell / Jessica Olah

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 because the higher your body temperature, the colder the air feels.

A fever is the body's defense against the flu virus. Viruses thrive at a normal body temperature of 98.6 degrees F, and while uncomfortable, running a fever helps your body fight off the flu. Whether or not to treat the fever depends on how high the temperature is and the person’s age. 

A low-grade fever (98.7 to 100.4 degrees F) is typically not a concern for adults or most children. It may be best to let a mild fever run its course. However, if you are very uncomfortable or the fever reaches 102 degrees F, bringing the fever down slightly is advised. Use these tactics:

  • Consider appropriate fever-reducing medications, such as acetaminophen, ibuprofen (over the age of 6 months), or aspirin (in adults only)
  • Try a lukewarm bath or sponge bath.
  • Avoid bundling up, as this can increase your body temperature.

A rectal temperature of 100.4 degrees F in babies 3-month-old and younger or 102.2 degrees F in children under a year warrants a call to your doctor.

In children over a year old and adults, a temperature above 105 degrees F is cause for concern. A very high fever (over 107.6 degrees F) can lead to brain damage and is considered a medical emergency.

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, and fatigue is often so severe that it is hard to just get out of bed. This exhaustion is much more pronounced than the tiredness you may feel from a cold.

Aches and Pains

Feeling "achy" is how many people with the flu describe their state. 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 have 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.

Headache

Headaches are common with the flu and can be quite severe, compounding your level of discomfort. Taking an over-the-counter (OTC) pain reliever like acetaminophen or ibuprofen may help.

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.

Rare Symptoms

Vomiting and diarrhea are not common flu symptoms for most people, but some do experience them. Children are more likely to have vomiting and diarrhea with influenza than adults.

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

Complications

For most people, flu symptoms resolve in one to two weeks. Complications are typically mild, such as sinus or ear infections. The flu can, however, be serious and life-threatening. In fact, there are 12,000 to 61,000 deaths from influenza in the United States each year.

Serious complications of the flu can include: 

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

High-Risk Groups

Those at higher risk of complications from the flu include:

  • Adults ages 65 and older
  • People who are pregnant
  • Children under the age of 5
  • People with chronic medical conditions such as asthma, diabetes, and heart disease
  • Those who are immunocompromised

When to See a Doctor

If, based on the symptoms, you believe you may have the 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 an antiviral 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, or you develop a fever or productive cough after you have started to feel better. This could indicate a secondary infection, such as bronchitis and pneumonia.

Other symptoms that require a call to your doctor include severe muscle pain, weakness, or unsteadiness, and any worsening of chronic medical conditions.

When to Call 911

The flu can quickly take a turn for the worse and may require emergency care. If you experience any of these symptoms, seek immediate medical attention as they may be a sign of serious or life-threatening complications:

  • Difficulty breathing or shortness of breath
  • Persistent pain or pressure in the chest or abdomen
  • Persistent dizziness, confusion, inability to arouse
  • Seizures
  • No urination
  • A fever above 105 degrees F that does not respond to medication

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 eight hours, dry mouth, no tears when crying)
  • Not alert or interacting when awake
  • Seizures
  • A high fever (above 100.3 in infants under 12 weeks of age, above 102.2 degrees F in children under a year, or above 104 degrees F under the age of 12) that does not respond to medication
Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Flu symptoms & complications. Updated September 18, 2019.

  2. MedlinePlus. Fever. Updated February 4, 2020.

  3. Centers for Disease Control and Prevention. Disease burden of influenza. Updated January 10, 2020.