Ever taste blood when you’re running? This doctor explains why

A photo of a young woman after going for a run
(Image credit: Shutterstock)

If you’ve ever tasted blood in your mouth when you’re running and wondered what’s going on, well a Miami-based doctor as the answer. A TikTok video, posted by the account lifeofadoctor, has amassed over 3.5 million views, as thousands of runners seek to find out exactly what is happening when they get that horrible, metallic, bloody taste at the end of a hard workout.

The good news is that it’s not really something to worry about, and definitely not an excuse to not go running. According to research, this taste sensation is more likely to occur when running in cold, dry air, when you’re doing a really intense session, or if you’re training at altitude. So as the weather starts to change, you might be more likely to experience this bloody taste, especially if you’re upping your training ahead of a spring marathon. 

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♬ original sound - LifeOfADoctor

Why do you taste blood when running? 

So, let’s cut to the chase — what exactly is going on when you taste blood when running? The TikTok doctor explains: "Alright this is going to blow some minds. If you ever went running and tasted blood, it’s actually because you were bleeding into your lungs." 

I’ll pause here to say, I know what you’re thinking, what?! But the doctor goes on to explain that this tiny amount of blood won’t actually cause you harm. 

"So when you start exercising, your blood pressure goes up, and there are these tiny sacs deep within your lungs where blood runs through to get oxygenated" he said. "When that blood pressure gets high some of those burst open, releasing blood into your lungs, so when you go to exhale, that blood gets taken up into your windpipe and into your mouth, and from there your tastebuds pick it up." 

Responding to a comment that questioned whether tasting blood should be taken as a sign to stop running, the doctor responded, "just to clarify, it’s a TINY TINY amount, so this is not an excuse to stop exercising!" 

That said, it goes without saying that if this happens to you very often, or you’re coughing up blood on a regular basis, it’s definitely worth going to chat to your doctor. But, if you’re a healthy person, and have sometimes tasted blood during a cold, winter’s morning run, this is probably why. 

Jane McGuire
Fitness editor

Jane McGuire is Tom's Guide's Fitness editor, which means she looks after everything fitness related - from running gear to yoga mats. An avid runner, Jane has tested and reviewed fitness products for the past five years, so knows what to look for when finding a good running watch or a pair of shorts with pockets big enough for your smartphone. When she's not pounding the pavements, you'll find Jane striding round the Surrey Hills, taking far too many photos of her puppy.