For some people, a competitive streak is just in the blood. But for two Toronto-area men, that competitive spirit has had a life-saving side effect for dozens of people they've never met.

Peter Slykhuis and Alan Flewelling, both 52 and residents of Mississauga, have been friends since they met decades ago at the University of Toronto. They’re now both chartered accountants and investment bankers.

Because they work at competing firms in Toronto, they’re used to fighting for dominance. But recently, the pair has been involved in a friendly little race to donate the most blood.

“It's just in our nature. We've been friends forever and we're just a little competitive,” Flewelling explains.

The competition started about a decade ago when they realized they were both regular blood donors. It soon became a numbers game for them.

“Every time he made a donation, he would send me an email with the number of his donation. He was just sticking it to me a little bit,” Slykhuis says.

Over the years, they've gone back and forth at the top of the unofficial leaderboard.

“I was ahead for a while,” says Flewelling. “Then Pete caught up by donating platelets, and then he was ahead of me actually.”

Platelet donations, it turns out, can be done every two weeks, while donating whole blood can only be done every eight weeks, which is the time needed to allow the body to replenish its red blood cells.

Then this year, the two realized they were on their way to becoming top donors and reaching a milestone.

“We finally decided to declare a truce and that we'd do our 100th donation together,” says Slykhuis.

The men are now two of only 17 people in Mississauga, Ont. who’ve donated 100 or more times.

Of course, even during that donation, they couldn’t help themselves from competing -– Flewelling’s donation wrapped up a minute earlier than Slykhuis’, so he sees himself the winner.

But there's also another winner in this competition, says Canadian Blood Services’ Laura Ashton.

"They’re helping to ensure that the patients who need the blood are going to receive it," she says of the friendly competition.

The friends now have their sights on their next milestone. “The race is on for 200,” says Slykhuis.

With a report from CTV Toronto’s Calvin To