“Coach B., is it okay to pee blood after a run?”

The question came from a high school runner as he scrutinized the contents of his urinal. It looked like pink lemonade, and he remarked in a chagrined sort of way on this resemblance.

As I examined the offending piss, rather chagrined myself, another runner interjected. “Oh, don’t worry about it. It happens to me after soccer games sometimes.”

I wasn’t so sure. I had never peed blood after a run, and I’ve been on some pretty demanding runs. I was concerned enough to do some research… for both of their sakes.

It turns out the second runner, the soccer player, was correct; peeing blood after exercise really isn’t too uncommon. It’s called Haematuria, and it often happens to active humans. In fact, samples taken from marathoners post-race have returned 20-30% positive results (Lam). The difference is in how much blood is in the pee. Most of the time, it can’t be seen with the naked eye. Humans, being visual creatures, don’t panic until they can actually see the red blood cells leaving their body.

Some people seem more susceptible to this more alarming phenomenon than others. Why that is, physiologists still debate. Some possibilities include:

1. Damaged red blood cells in the feet from impact with the ground. Don’t worry- this doesn’t happen to everyone. It seems to only affect people with unusually fragile red blood cells (Dr. Andrew Bosch).

2. Dehydration. One of the oldest and most pervasive enemies to runners, it may be the root of yet another malady.

3. A whole host of other things, including…

“…renal ischaemia (lack of adequate blood flow to the kidneys), hypoxic damage, the release of a haemolyzing factor during exercise, bladder and/or kidney trauma associated with exertion, the use of non-steroidal anti-inflammatory drugs… and the peroxidation of red blood cells which is an inevitable feature of sustained aerobic exercise

(‘Sport-Related Haematuria: A Review,’ Clinical Journal of Sport Medicine, Volume 7(2), pp. 119-125, 1997).

So if you’re seeing blood after your runs, you probably still want to consult a doctor- but don’t, as I would have, get too worked up over it.

Glad I didn’t have any pictures this time?