Is It the Flu? 8 Most Common Flu Symptoms in Adults
Key takeaways:
Body aches, cough, and runny nose are the most common flu symptoms in adults. Fever, headache, and weakness are also common symptoms.
Flu symptoms in adults usually come on suddenly, peak after a few days, and go away after 1 to 2 weeks. Symptoms are more severe in people who haven’t been vaccinated.
It’s important for people at high risk for complications to get medical attention for flu symptoms. Treatment works best when started within the first 2 days of symptom onset.
Table of contents
You’re probably aware of the many different respiratory illnesses floating around in wintertime, like the common cold, COVID, and flu. These illnesses often have overlapping symptoms. So when you start to feel sick, it’s common to wonder what your symptoms might mean.
Here, we’ll review the most common flu symptoms in adults and discuss when you should consider getting medical attention for them.
What are the most common flu symptoms in adults?
Flu symptoms in adults tend to show up suddenly. They usually start within a couple of days of being infected and peak around day 3 or 4 of illness. Most adults with the flu feel sick for about a week, although symptoms can sometimes last longer.
Body and muscle aches
The most common symptom among adults with the flu is myalgia, or muscle aches. This can affect almost any muscle in your body, even your eye muscles. Research suggests almost all adults with the flu will experience myalgias, and they can be miserable. Some describe it as feeling as though they were “hit by a train.”
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Cough
A dry cough is also a very common flu symptom in adults. But it’s common in many other respiratory illnesses as well, so it’s not specific to the flu. That said, research suggests the combination of fever and cough in the first 48 hours of an illness is a pretty clear signal of the flu.
Unfortunately, this cough can persist for a week or two, even after the other symptoms have gone away.
Headache
Headaches from the flu usually occur early in the illness and are very common. They can be due to sinus pressure, dehydration, and/or your body’s response to the virus. How long the headache lasts can depend on how long your congestion lasts and how well you stay hydrated.
Flu headache typically feels like aching or throbbing all over your head. The flu can also trigger migraine headaches in those who are susceptible to them.
Nasal congestion / runny nose
This is one of the most common flu symptoms in adults. Over 90% of people with the flu have nasal congestion and/or runny nose. But like a cough, this isn’t specific to the flu. Runny nose and congestion can last the entire week of your flu symptoms.
Fatigue / weakness
The extreme tiredness and weakness that come with the flu, combined with muscle aches, tend to make the flu feel worse than other respiratory illnesses. Weakness affects up to 94% of adults with the flu. It can make it difficult to perform daily activities, making your bed or couch the best place to be.
How long will it take to feel better? Our experts review the typical flu recovery timeline and share tips to help you recover faster.
Isolating with the flu: Here’s how long you’re contagious with the flu.
Over-the-counter (OTC) flu remedies: There are lots of OTC flu and cold remedies on the market. A pharmacist shares tips on choosing the best one for your symptoms.
Fever
Fever, defined as a temperature over 100.4°F (38°C), isn’t as common as the other symptoms listed above. In other words, it’s possible to have the flu without a fever. This is especially true for older adults.
For those who do get a fever, it usually appears early in a flu illness and lasts for a few days.
Sore throat
Sore throat is a symptom for about 84% of adults with the flu. A sore throat may make swallowing painful, which can make it difficult to stay hydrated. It may also make your voice hoarse.
If you have a sore throat without the other flu symptoms, it could be caused by something else, like strep throat.
Diarrhea
Although the flu is primarily a respiratory infection, it can also cause gastrointestinal problems like diarrhea. This isn’t a common flu symptom in adults, as kids are more likely to get diarrhea when they have the flu. But adults can develop flu-related diarrhea. It can last between 2 and 5 days.
How do you treat adult flu?
Most people recover from the flu with home remedies and over-the-counter (OTC) medications like:
Rest
Drinking fluids
Nasal saline rinses
Fever reducers (like ibuprofen, acetaminophen)
Some people may also benefit from prescription antiviral medications like Tamiflu. These medications work best if taken within the first 2 days of flu symptoms. Antiviral medications take 1 to 2 days to kick in, but they can shorten the duration of illness.
Be sure to stay home while you’re sick to avoid spreading the flu to others.
When should you get medical care for flu symptoms?
You should seek medical care right away if you have flu symptoms and any of the following:
Chest pain
Difficulty breathing
Severe weakness or fatigue
Ongoing dizziness or lightheadedness
Not urinating (due to dehydration)
Symptoms that don’t improve or worsen after 1-2 weeks
These could be signs and symptoms of a severe illness or mean something else is causing your symptoms. You may also be developing a complication or an additional medical issue due to the flu infection. Examples of flu complications include bronchitis and pneumonia.
Some adults are at higher risk for flu-related complications, including those who:
Are over age 65 years
Have chronic health conditions, like lung disease
Have a weakened immune system
Are pregnant
If you’re at high risk for flu complications, it’s best to get medical care earlier in your illness. You can also consider seeing a healthcare professional to get tested for the flu. You’ll get immediate results, along with a prescription for antiviral medication.
Frequently asked questions
It’s common for flu symptoms to come on suddenly and get worse before they get better. Most people feel very tired and may struggle to get out of bed for a few days. Flu-related fever and muscle aches can be pretty uncomfortable. It’s also common to have a nagging, dry cough for several days after the rest of your symptoms have gone away.
This isn’t the same for everyone. Some people report a “tickle” in the back of the throat first, while others might have fatigue or a stuffy nose. But because symptoms develop pretty quickly, the first symptom will soon be followed by the others.
The best prevention against the flu is the yearly flu shot. This is especially important for people at high risk for severe illness and complications. Flu vaccines protect against severe illness from both influenza A and B. They also make flu symptoms in adults less severe.
The bottom line
The most common symptoms of flu in adults include muscle aches, cough, runny nose, fever, and headache. Gastrointestinal symptoms, like diarrhea, are possible but much less common. If you’re over 65 years of age, pregnant, or have chronic medical conditions, it’s best to get early medical attention for your symptoms. This way, you can get effective treatment and help prevent severe illness or complications.
Why trust our experts?
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MedlinePlus. (2024). Flu.
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National Headache Foundation. (n.d.). What your flu headache is telling you.
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UPMC Health Beat. (2022). What are the early signs of the flu?
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