Under the Weather? Here’s How to Tell If You Can Still Go for a Run While Sick

On the one hand, you feel not so great, and running isn't exactly the number one thing you should do with your time. But on the other, you hate to miss an endorphin-boosting sweat sesh, no matter what the conflict du jour may be. (Personally, I hit the treadmill while sick, so I'm guilty of the aforementioned stubbornness.) This is, of course, in terms of non-severe illnesses—you should definitely ditch running when afflicted with something more serious than a cold or flu.

In the past, I've heard a saying that if your sickness is from your neck and up, you're okay to run—anything below your neck (i.e. your chest) means you should take a rest day. This would put having a sore throat in the good-to-go category and something like a respiratory infection in the other (as in: don't do it). But to truly determine when, on your level-of-sick spectrum, it's still okay to run and when you should ditch your running gear in favor of Netflix, I consulted the pros.

"It really depends on what kind of sickness you're dealing with," says Robert Segal, MD, physician and founder of Medical Offices of Manhattan and co-founder of LabFinder.com. "Bottom line is that there's a reason why nature made us feel sick and you should listen to your body. If you feel sick enough to miss a day of work, you should not go for a run."

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You've got the green light to go running while sick if...

There are some types of sicknesses in which it's totally fine (sometimes even encouraged) to get a run in, and fitness can be your cold symptoms' friend. "If your symptoms are congestion related, like a runny nose, chest congestion, or coughing, you're usually safe to run," says Dr. Segal. "In fact, a light run followed by rest and a hot shower with steam may ease the congestion and make you feel a little better." It's true—there have definitely been times when I've gone for a run with a mild cold and finished feeling like a million bucks.

That's not to say you can go all out, sprinting up hills or trying to break your personal record in marathon training. When you're under the weather yet. Still planning on keeping your workout pretty low-key. "I'd recommend taking it easy and reducing the speed and intensity of your run," says Dr. Segal. So aim for more of a jog pace than full-on speed racer—doctor's orders.

When to skip your run if you're feeling sick

When you're feeling really flu-like or hotter than usual is when you should miss your run. "Running with the flu or flu-like symptoms—especially achy muscles or a fever—is not a good idea," says Dr. Segal. Going for a run with a fever is particularly bad, he adds. "Running with a fever is not only dangerous but will significantly increase the time it'll take you to get back to normal."

He explains that a fever occurs when your body is trying to fight bacterial or viral infections, which cause a rise in your internal temperature. "This is your body’s natural defense mechanism against the infection, and helps your immune system clear the infection," says Dr. Segal. "Running compromises the immune system, particularly in the first 20 hours after strenuous exercise. Your body will be more susceptible to the bacteria and viruses already making you unwell, which increases the likelihood of your symptoms taking a turn for the worse."

Besides this, running (obviously) makes you sweat, which increases your internal temperature—and that's not good news for your sickness. "That will make your fever symptoms even worse and could result in dangerous and long-term health consequences," says Dr. Segal. Also, running uses up critical energy that you really need in fighting your infection, whether it's a cold or a flu. "Running siphons away energy, nutrients, and resources that could be used to help fight the virus, thereby lengthening the amount of time it takes you to return to full health," he explains.

Basically, you should really listen to your body and not go against it just to get in a workout—you can make things worse for yourself, after all. It's also key to remember that missing a day or two of running will not sidetrack your fitness game. "Take as many days as you need in order to feel back to normal with your everyday activities," says Dr. Segal. "Remember, it takes at least 10 days to lose significant running fitness, so don't be worried that a few days off to get healthy will ruin your training." Plus, who doesn't love a legit and doctor-approved excuse for a day of R&R?

Oh, and these are the most common running injuries and how to fix them. And this is how to get back into running if you've lost your mojo. 

Originally posted November 18, 2018, updated December 19, 2019