If you've ever tasted blood in your mouth while running and wondered what's going on, a Miami-based doctor has the answer: a TikTok video posted by an account called lifeofadoctor has received over 3.5 million views, and thousands of runners are trying to figure out exactly what's going on when they have that hard trying to know exactly what is going on when they get that horrible, metallic, blood taste at the end of a workout.

The good news is that it's really nothing to worry about and definitely not an excuse not to go for a run. Studies have shown that this taste is more likely to occur when running in cold, dry air, during really intense sessions, or when training at altitude. As the weather begins to change, you may be more likely to experience this bloody taste, especially if you are increasing your training in preparation for a spring marathon.

If you are a runner and are looking to upgrade your running kit, why not check out our summary of the best running shoes for 2021, the best sports bras for running, or the best women's running shoes on the market?

So let's cut to the chase - what the heck is going on when you taste blood while running, explains a TikTok doctor: "Now, you might be a little surprised. If you've ever tasted blood while running, it's actually because your lungs are bleeding."

I know what you are thinking! But the doctor goes on to explain that this tiny amount of blood will not actually harm you. [When you start exercising, your blood pressure rises, and there are little sacs deep in your lungs through which the blood passes to take in oxygen. So when you try to exhale, that blood is drawn into your trachea and into your mouth, where your taste buds pick it up."

In response to a comment questioning whether the taste of blood should be taken as a sign to stop running, the doctor replied, "Let me be clear, it is a tiny amount, so this is not an excuse to stop exercising!" I replied.

Nevertheless, it goes without saying that if this happens frequently or if you regularly vomit blood, it is worth consulting your doctor. But if you are a healthy person and have tasted blood from time to time during a cold winter morning run, this is probably the cause.