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The day you notice flu symptoms probably starts as usual – you get the kids off to school, head to work, and put your lunch in the fridge. Then your body starts to ache, and you notice a tickle in your throat. Chills might come next. “Uh oh,” you think. “Could I have the flu?”


September 18, 2023

You did everything you could. You diligently washed your hands, sanitized the kids’ toys after playtime and got plenty of sleep. You read all of the latest news articles about when the flu might hit your town, cooked healthy, well-balanced meals for family dinners and kept the kids home from play dates with the Johnsons when you heard they were recovering from a nasty bug. You even got your annual flu shot. But, sometimes, viruses, like the ones that cause the flu, can infect your home when you least expect it.

The good news is, though, that understanding the early signs and symptoms of the flu can not only help you spot the flu faster to prevent the spread of the flu virus to others – kids, spouses, coworkers, neighbors and friends – but can also help you start to treat the illness before it gets worse. In fact, certain antiviral medications can help lessen symptoms and shorten the time you are sick by one or two days. However, these medications are most effective when taken within 48 hours of the onset of flu symptoms, which is why it’s important to recognize the flu – and fast.1 What are some of the early signs that you may be coming down with the flu? And what’s really happening to your body when you have those aches and pains, fever and chills?

Here are some tips to help you get to know the flu better – and learn the early warning signs – so that you can get back on your feet faster.

girl coughing in elbow

1. First Symptoms of the Flu

You clear your throat, sip warm tea and cough – but it always comes back. It’s that pesky itch at the back of your throat that just won’t go away, no matter how much you swallow, sip, cough or clear. While it’s certainly an annoyance, a tickle at the back of your throat could be a sign that you may be coming down with the flu (or another virus or illness). A sore, scratchy throat signals that white blood cells and antibodies are rushing to the area to fight infection – causing inflammation and irritation. 

MedExpress Pro Tip: Sip warm tea. Not only does tea soothe a sore throat, but it also helps keep your body hydrated, which is especially important when fighting flu viruses.

What’s the difference, though, between a sore throat caused by the flu or another infection and a sore throat caused by allergies? If your sore throat is paired with sneezing and itchy eyes, two symptoms that are less common with flu, allergies are likely the culprit.

You don’t want to wait for the tickle to turn into a stubborn sore throat. At the first sign of a back-of-the-throat itch, give your immune system a powerful boost with important key nutrients and vitamins, like vitamin D and vitamin C, both of which your body needs to fight infection. Vitamin D strengthens the immune system and fights against disease. Vitamin C, which can be found in fruits and vegetables as well as taken in supplement form, can also help shorten the duration of flu symptoms – but remember that overdoing it won’t help! Any extra vitamin C will go to waste and simply be flushed out of your body in your urine.

top view of mug of tea

2. Body Aches and Chills: Take Them Seriously

It might start as a headache. Then, slowly but surely, your entire body starts to ache. And pretty soon, moving even a muscle can be painful. You may blame your achiness – which commonly manifests in the legs, back or head – on a recent workout or the yardwork you did over the weekend. However, body aches are another early sign that the flu might be headed your way – in fact, those not-so-fun, all-over body aches are often an indication that your body is releasing inflammatory chemicals to help your white blood cells fight off infection. So, don’t brush off these symptoms – give your body a much-needed break and take a warm bath to help soothe sore and uncomfortable muscles.


In addition to aches and pains, chills are another tell-tale sign that your body may be fighting off a virus. In fact, chills are often one of the first symptoms that people notice when they’re coming down with the flu. That’s because when the immune system first recognizes an “invader” that threatens the body’s equilibrium, it quickly jumps into action and produces heat – through rapid muscle contraction and relaxation – to try to fight the infection. These rapid muscle contractions result in the chills – or shivers – we know well. Many people believe that chills only occur when a fever is present, but that’s not always the case. Most often, chills actually precede a fever and can even occur without one.

MedExpress Pro Tip: It can be tempting to bundle up under heavy blankets or layers of clothing to keep yourself warm when you have chills. But covering up in too many layers can actually cause your body to overheat. When it comes to relieving those shivers and shakes that make you go “brrrr,” it’s best to simply get plenty of rest, drink lots of liquids and cover yourself in a light sheet or blanket to stay warm.

3. Let a Fever Run its Course

The body does some pretty incredible things to protect itself. Cilia, for example, are the tiny hairs that line the inside of our respiratory system to protect us from pollutants in the air we breathe, like dirt. Our stomachs produce acid that helps kill dangerous germs that could invade through the food or drinks we consume. But perhaps one of the most fascinating ways that the body protects itself is with a fever.

A fever is part of our body’s natural response to invaders and is a very common early sign that your body is fighting an infection like the flu. It may come on quickly, and like other early flu symptoms, is an important step in the body’s quest to get healthy. Many viruses, including those that cause the flu, thrive at the body’s normal temperature – 98.6 degrees Fahrenheit. So, when the body recognizes an unknown invader, the immune system steps in and heats up the body’s core to a temperature that is not ideal for those germs to reproduce.

While a high fever can be dangerous and may require medical attention, a mild increase in body temperature when otherwise healthy adults and children are under the weather is completely normal – and is actually a good sign that your immune system is in working order. In most cases, it’s completely safe, and even recommended, to let the fever run its course – allowing it to break on its own.

man grabbing his lower back

4. Feeling Fatigued? Rest is Key

If you start to feel sudden or excessive fatigue, exhaustion or just generally run down, it could be a sign that your body is fighting off a bug. Exhaustion is a symptom of both the common cold and flu, but is typically more debilitating with the flu, and often means you may be too tired to even get out of bed or move off of the couch.

So why is sudden exhaustion one of the first symptoms you’ll notice when you come down with the flu? Because your body needs more energy to mount an effective immune response against flu viruses. When we’re sick, our immune systems spend more energy creating immune cells and proteins, like antibodies, to fight the infection and require more “fuel” to support their growth and production.

MedExpress Pro Tip: There’s a reason why your doctor might prescribe some quality R&R when you have the flu. Getting a good night's sleep, resting your body and taking off a day or two from your busy routine can help your body successfully produce the antibodies and other germ-fighters it needs to kick  the infection − so you’re back on your feet faster. After all, isn’t that what sick days are for?

How Long Does the Flu Last?

People who do not develop serious flu complications will get better in a few days to less than two weeks.3 Fortunately, the worst part of the flu is usually over in a few days. Here are typical stages of the flu:4

  • Day 0: You may not have any symptoms yet, but the virus has been contracted.
  • Days 1-4: Flu symptoms will start to appear and are usually more sudden than those of a cold. Look out for fever, fatigue, chills and other signs of the flu. You are likely to be most contagious during this time.
  • Days 5-7: Flu symptoms will start to subside, although you may still feel tired.
  • Day 8 and beyond: Symptoms should either be gone or getting better. Even though you may be feeling better, it is possible to still feel fatigued for several weeks after.

It's important to note that flu symptoms can vary from person to person, and some individuals, such as the elderly, young children, or those with weakened immune systems, may experience more severe complications. Always consult a health care professional for proper diagnosis and treatment if you suspect you have the flu.

Those at highest risk for complications from influenza, have a risk window that extends out as far as two weeks post infection when they are more susceptible than the rest of the population to acquire a bacterial pneumonia after their lung tissue has been weakened or damaged by influenza, so be especially watchful for rebound or lingering illness.

How to Tell If it is the Flu or COVID-19? 

How do you know if it’s the flu or COVID-19? Compared to the flu2, COVID-19 may cause more serious illnesses in some people. It can also take longer for symptoms to appear and it remains contagious for a longer period. Some of the symptoms of flu, COVID-19 and other respiratory illnesses are similar and its possible to be infected with more than one of them at the same time. That’s why testing at your neighborhood MedExpress center is necessary to confirm what illness you have. 

Knowing the early signs and symptoms of the flu – and understanding what they mean for your body – can help you treat the virus faster and prevent the spread to loved ones, friends and coworkers. If you have any of these symptoms, it’s important to talk to a healthcare professional, like MedExpress, to seek appropriate treatment, especially during flu season when these viruses are common.

Originally posted December 17, 2017. Updated September 19, 2023.

This content was medically reviewed by a MedExpress physician.

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1 Centers for Disease Control: What You Should Know About Flu Antiviral Drugs. Last updates December 15, 2022. Accessed July 26, 2023.

2 Centers for Disease Control: Similarities and Differences between Flu and COVID-19​. ​Last updated June 7, 2021. Accessed July 1, 2021.

3 Centers for Disease Control: Flu Symptoms & Complications. Last updated October 3, 2022. Accessed July 26, 2023.

4 Centers for Disease Control: How Flu Spreads. Last updates September 20, 2022. Accessed July 26, 2023. 

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