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Taste blood when running? 7 causes + ways to prevent it


There are a range of familiar sensations and feelings when it comes to running, such as heavy breathing, stiff and sore muscles, and profuse sweating.

However, some of these sensations are not so familiar. 

When you taste blood when running, it may come as a surprise or even shock. 

Some runners describe it as a metallic taste in their mouth, others describe it as a weird or bad taste in their mouth. 

But what exactly causes that blood taste when running? Is it a sign of something more sinister, or is it a benign phenomenon?

In this guide we’ll explore:

  • What causes you to taste blood when running?
  • Is it bad to taste blood when running?
  • Who can taste blood when running?
  • How to prevent blood taste when running


Let’s get started!

taste blood when running

What causes you to taste blood when running?

The unmistakable metallic or blood taste in your mouth when running or after exercise could have a range of different causes.

The two main causes and theories are:

  1. High blood pressure
  2. Cold air inflammation

#1 High blood pressure

According to researchers at the Norwegian University of Science and Technology (NTNU), the taste of blood normally happens when you do high intensity exercise, which increases your heart rate and raises your blood pressure.

When this occurs, oxygen-rich blood is pumped through your lungs out to your muscles.

Blood cells passing through your lungs pick up oxygen and release carbon dioxide, which you exhale. 

High blood pressure can make the tiny blood vessels in your lungs break open a little, which enables some blood to reach the surface of the tiny air sacs in the lungs called alveoli. 

Researchers have concluded that the iron smell of the blood on the surface of the alveoli probably leaks out when you exhale. 

So importantly you are not getting blood in your mouth. If you do, it is normally a sign of a disease. 

#2 Cold air inflammation

When you breathe through your mouth, a huge rush of cold air comes through the mouth and enters the lungs which could be a source of irritation.

This rush of air can cause minor tears in the delicate linings of your airways, which then allows small amounts of blood to enter the airways. 

This is particularly worse when you run in a cold, dry environment and at high altitudes. 

It’s during these types of runs that the heart must work harder than it’s conditioned to work, therefore leading to a buildup of fluid in the lungs known as pulmonary edema.

When this fluid builds up, the increased pressure leads to leakage of red blood cells into the small air sacs in the lungs.

Related: Running with a cold: Is it good or bad?

taste blood when running

Other potential causes of blood taste when running

Here are other potential causes of that blood taste in your mouth:

#3 Medications and supplements

Some medications like antibiotics, antidepressants and blood pressure and diabetes medications may have blood taste side effects.

In addition, supplements like multivitamins, especially those with heavy metals or irons can cause a blood taste side effect.

#4 Allergies

The runny nose and itchy eyes that come from having allergies may contribute to that metallic taste in your mouth.

This is because allergy medications (such as antihistamines) may lead to increased secretions in the respiratory passages and cause a metallic taste and dry sensation in the mouth.

#5 Pregnancy

Pregnancy is one of the more common causes of metallic taste in the mouth.

It is likely caused by hormonal fluctuations that arise from being pregnant.

This sensation is normally temporary during pregnancy. 

#6 Poor dental hygiene

Neglecting dental hygiene can lead to bad breath, cavities and the taste of blood in your mouth.

If you don’t brush your teeth for 2 minutes twice a day, you risk getting gum disease which can cause inflammation of the gums. 

#7 More serious, underlying health conditions

If you regularly taste blood during and after exercise, then this may be a sign of a more serious underlying health condition.

Don’t just ignore the taste of blood in your mouth – even if you think the underlying cause isn’t serious.

Anyone who tastes blood should visit their healthcare professional, especially if you’re not sure why you’re experiencing the sensation. 

Neurological conditions such as Bell’s Palsy and dementia are normally associated with a metallic taste in the mouth. Diabetes can also have an effect. 

Related: Runner’s toe: Causes + 6 ways to prevent it

Is it bad to taste blood when running?

Experts generally agree that tasting blood after exercise is not uncommon, but generally it is seen as a benign sensation.

The blood taste may be unpleasant but is not dangerous in most cases. 

Don’t automatically assume you have a serious condition if you ever taste blood in your mouth.

You will probably have other new or unusual symptoms if you have a more serious condition.

Related: Does running burn belly fat?

taste blood when running

Who can taste blood when running?

Researchers believe the blood taste when running is more common in runners who are in poor shape.

Typically, it’s more common in people who haven’t done much exercise before and they start with a hard aerobic session. 

As you improve your fitness and aerobic capacity (also known as VO2 Max), the blood vessels in your lungs will grow stronger and will become more capable of handling high blood pressure. 

Professional athletes can also experience it, but less often. 

Related: How to breathe when running

How to prevent blood taste when running

Now you know more about the blood taste when running, here are some prevention tips.

#1 Warm up before each run

Warm up properly before each run, especially before high intensity exercise such as speed training. 

Your arteries and capillaries expand as your body temperature rises, so even more reason to gradually raise your heart rate by doing a warm up before your run.

If you start too hard, you are more at risk of getting that taste of blood in your mouth.

A proper warm up will consist of jogging and dynamic stretches to get your heart rate up and loosen your muscles.

#2 Reduce the intensity of your runs

If you regularly taste blood when running, then it’s a sign that you need to reduce the intensity of your runs. 

Whilst there’s no immediate danger, the blood taste is a signal from your body that you need to take things a little easier.

#3 Take care when working out in cold, dry environments

If you regularly train in cold, dry environments or at high altitudes, then you will need to take more care to avoid the blood taste when running.

Alter the intensity of your runs when running in the cold or at high altitudes so to relieve some of the pressure on your lungs.

#4 Breathe through your nose

When you breathe through your nose, the air is heated up on the way in, which is far easier for your lungs to tolerate.

Caroline Geoghegan