How long do the flu symptoms last? Here are more flu answers from The Survival Doctor:

by James Hubbard, MD, MPH

Doc, how call I tell the flu from a cold? Should I get seen? How long do the flu symptoms last?

Both online and in clinic, I get a lot of questions about the flu. In this post I’ll answer some of the most commonly asked.

Q: How do I know if I have the flu?

A: When seeing a patient for aches, pains, and fever, here are some of the clues that make me think I’m dealing with the flu:

  1. It’s going around. While there’s a chance for flu anytime, it’s much more likely in winter, late fall, or early spring.
  2. The person looks ill and essentially tells me they feel like they’ve been beaten up and then kicked some more.
  3. They say they were feeling fine and then, out of the blue, started getting chills and muscle aches. Quickly, they felt like they’d just run a marathon and then been stuck in a blender.

Most of my patients with the flu are fatigued and their muscles hurt, down to the bone. The fever goes up to 102 or higher—maybe even 106. There could also be a cough, headache, and sore throat.

In some lucky few, though, the symptoms are very mild, kind of like a cold with low fever. Sometimes it’s hard to discern whether they really do have the flu.

And I always look for other reasons for the symptoms. Shortness of breath or rales in the chest would make me suspect pneumonia.

Why Now?

Q: Why is the flu more common in the fall and winter?

A: We’re not sure why. Some surmise it may be because the virus lives better in cold, dry air. Or it could be because we get less sunshine in the winter and, hence, less vitamin D, which makes us more susceptible.

Those may play a role, but most experts still adhere to the theory that we stay inside more in the winter, and since the virus spreads through the air, we’re more likely to be exposed in enclosed areas.

Even in warm-weather areas of the country, where the winters might not get so cold that people stay inside more, people travel in and spread it. As more sick travelers than usual come in, everyone gets exposed.

Q: Does the flu test work?

A: The flu test can confirm you have the flu. But it’s not great at catching all flu cases. It’s incorrectly negative as much as 20 to 40 percent of the time. There is a new test that probably will be available soon that should be more accurate. A viral culture is much more accurate but must be sent to a lab, takes a couple of days to get back, and is very expensive.

Secondary Infections

A secondary infection is one you get in addition to the flu. It can be viral or bacterial (which might respond to antibiotics). Any should be checked out.

A secondary infection can happen during the flu, but another typical scenario is you’re getting better and suddenly get worse. Maybe the fever is gone for a day or two and suddenly comes back.

Common secondary infections with the flu include:

Q: What are some other illnesses that can be mistaken for the flu?

A: If you’re sneezing and feeling bad with no fever, you might have allergies. If you have a little sneezing with a low fever, it could be a cold.

And here’s a common confusion. A sore throat, high fever, and tender lymph nodes without the cough might make me want to do a test for strep throat.

Although vomiting and diarrhea can be part of the flu, if you have those symptoms alone, you’ve probably got a stomach virus or food poisoning.

Q: Why does it matter if you know whether it’s the flu?

A: While it’s true that with any virus, the general treatment is rest, fluids, and time, if you have the flu, you should take extra care. The flu kills people of all ages every year. Some people require hospitalization. Others get secondary infections and need antibiotics.

Here are some other reasons it’s good to know whether you have the flu:

  • If you have the flu, you’ll want to stay away from other people as best you can, to avoid spreading it further.
  • There are antiviral medicines that can help with the flu, especially in certain situations. More on that later.
  • You don’t want to miss a pneumonia or other illness that may need to be treated entirely differently.

Q: How long is the flu contagious?

A: From about a day or two before you even know you have it until about seven days after symptoms begin.

Q: How long do flu symptoms last?

A: Flu symptoms usually last anywhere from three to seven days. If they last longer than that, you should make sure it’s not something else. Although the fatigue and cough may linger for several weeks.

Red Flags

The flu can cause an overwhelming infection in some people. It can cause dehydration, and it makes you more susceptible for pneumonia. Every year, people die of the flu.

Here are some red flags—warning signs to get to the doctor right away. They’re not inclusive, so if you have worries, see the doctor.

  • Confusion
  • Shortness of breath
  • Severe headache that’s not helped by something like acetaminophen
  • Inability to keep fluids down
  • Lethargy to the point of being hard to wake up

Q: What is the treatment for the flu?

A: The flu is a virus, so antibiotics don’t help. Usually, you just mainly want to help your body fight the virus on its own.

As soon as you get the infection, your body starts producing antibodies to kill the virus. The antibodies developed will be specific for this strain but take a while to develop if they haven’t seen it before. For a few days, they’ll be in the catch-up mode.

You can help your body during this time by resting so it has more energy to focus on the fight. Also, eating will give it more fuel, and fluids will help keep the blood (and antibodies) flowing at their most efficient levels. Fluids will also keep the mucus that lines your airways moist so it can be coughed up easier.

You might try your favorite immune boosters. A vitamin D supplement is in vogue right now and may very well help. Some people swear by elderberry extract, aka sambucus. Some studies have shown it may help. Others, not so much. But it’s relatively safe. (However, always read up on side effects, etc., of any medicine, supplement, herb, or vitamin you take.)

Q: What about antivirals? Does Tamiflu work?

A: Prescription antivirals, such as Tamiflu (oseltamivir), have mixed results.

They work by trapping the virus so it can’t replicate. That means your antibodies have fewer invaders to fight off. All good. But these drugs are partially effective at best. In many people they do decrease the symptoms a bit and reduce the flu’s duration by a day or two.

Other down sides: In some people antivirals can cause nausea. And then there’s the expense of the drugs. Also, depending on the flu type, the virus may develop a resistance. (However, the main virus going around this year, 2015, has shown no resistance.)

Other up sides: Recent studies have shown antivirals can decrease your risk for complications, such as pneumonia. And they can decrease the severity of the flu enough to keep you out of the hospital.

So, for flu symptoms, you might want to check with your doctor, especially if you have a chronic disease, are 65 or older, or have a young child with symptoms. The antivirals work best if started within 48 hours of when symptoms begin.

Antivirals can also prevent flu symptoms altogether if you’ve been exposed. This not only lessens your risk but keeps you from exposing others.

Q: What else can I do to relieve symptoms?

A: Here are some home treatments to consider:

  • Keeping the fever down with something like acetaminophen (Tylenol) will make you feel better, and more likely to eat and drink fluids.
  • A cool-mist humidifier can help keep your airways moist.
  • If you wish, you can try your favorite over-the-counter flu medicines. Just make sure you know the ingredients and side effects. For instance, you don’t want to double dose on acetaminophen. In general, decongestants unclog you, antihistamines dry you up, guaifenesin may loosen mucus, and dextromethorphan or honey can suppress a cough.


  • Don’t take aspirin or anything that contains it. Especially in teens and children, that can increase the risk for developing a fairly rare but serious disease called Reye’s syndrome.
  • Don’t overdose on acetaminophen. A lot of flu remedies contain it. Read more here.


What kind of experience have you had with the flu? Did it hit you hard? Any complications?

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