You may encounter unexpected sensations when you run, from a nagging cough to unwelcome bowel movements. Many are harmless byproducts of the stress you’re putting on your body and are likely not a reason to be concerned.
Part of the running lifestyle involves encountering odd sensory experiences that may be hard to explain to others. The tricky part is deciding whether what you observe is just an oddity worth noting or something potentially dangerous worth reporting to a medical professional.
One of those symptoms a runner might incur during a workout is a sensation of tasting blood. You probably experienced a bloody nose or bit your tongue at some point, and therefore remember the distinct iron-laden taste of blood in your mouth and on your breath. But what if you experience this taste of blood, and there is no trauma to explain it? Some answers are more of an educated guess than a proven truth, but here are the most likely causes.
Your Mucous Membranes May Be Irritated
Let’s start with the simplest explanation: There can be a very small amount of blood leaking into your sinuses or oral cavity. This can occur when your mucous membranes (the soft tissue that lines our sinuses and inside of the nose, mouth, and windpipe) get irritated and leak a small amount of blood. The amount of bleeding in these conditions is usually so minimal that you wouldn’t see red when you spit, but the microscopic amount is all it takes for you to taste blood.
Conditions such as severe allergies, colds, coughs, and asthma might be triggers. Furthermore, poor oral hygiene or a dental condition such as gingivitis may contribute to this.
So, if you taste blood when you run, first examine if you have felt ill recently, had an asthma exacerbation, or haven’t been flossing like your dentist said you should.
Your Lungs May be Experiencing Increased Pressure
Another purported—yet unproven—reason for tasting blood on the run could be a circumstance of exercise-induced pulmonary edema (EIPE).
This phenomenon is well-documented in swimmers, where the pressure of the water outside of the body places extra stress on the lungs’ ability to expand and by extension, creates increased pressure at the alveoli (the precise location where your blood mingles with inhaled air). This increased pressure can cause blood to leak and additional fluid to accumulate where it doesn’t belong (into the part of the lungs where air travels). This process results in reduced oxygen intake per breath, and an irritation to the small airways of the lungs that may cause us to cough fluid and blood out of the lungs and into our oral cavity where we can taste it.
Although pulmonary edema in the context of activities such as swimming and scuba diving has been proven, not much research documents the same phenomenon at sea level. Articles in Pulmonary Medicine and the Races & Places How to Avoid Headaches After Running.
Heres How Stress Affects Your Running Performance Japanese Journal of Radiology confirmed pulmonary edema in a marathon runner, but the amount of edema needed to be detected on imaging also resulted in shortness of breath. What this likely means is that, even if a trace level of pulmonary edema occurs with running, it’s much less likely to be dangerous.
The Bottom Line on Tasting Blood on the Run
Remember that the taste of blood is almost always benign and often a reflection of you pushing your lungs to their current limit. If anything, it is a cue to review your training program Health - Injuries.
However, if the metallic taste becomes increasingly common on your runs, or if you start spitting or coughing up visible blood or feel short of breath as you exercise in addition to the taste of blood, it is time to see your primary care physician for an additional checkup.
Tasting blood on the run is more of a nuisance than a danger, but keep this info in mind to make sure something more serious isn’t happening.
Many are harmless byproducts of the. is an associate professor at the University of Pennsylvania. He is board-certified in Physical Medicine & Rehabilitation and Sports Medicine. He is a Team Physician for UPenn Athletics and medical director of the Broad Street Run and Philadelphia Distance Run, and previously for the Rock 'n' Roll Half-Marathon and Tri-Rock Triathlon in Philadelphia. He is a director of the running and endurance Sports Medicine Program at Penn Medicine. Dr. Vasudevan provides non-operative management of musculoskeletal conditions affecting athletes and active individuals of all levels, and combines injury rehabilitation with injury prevention. He utilizes a variety of ultrasound-guided procedures and regenerative approaches such as platelet-rich plasma and percutaneous ultrasonic tenotomy. He sees patients at the Penn Medicine and the Philadelphia Veterans Administration hospital. Dr. Vasudevan attended medical school at the University of Wisconsin School of Medicine and Public Health in Madison. After his Transitional Year in Tucson, Arizona, he went to residency in PM&R at Thomas Jefferson University in Philadelphia and onwards to Stanford University for his fellowship in Sports Medicine. He has been in practice at the University of Pennsylvania since 2012.
