Ringing up billions in medical bills is as easy as riding a bike.

Fatal and non-fatal bicycle injuries created $237 billion in U.S. medical costs between 1999 and 2013, according to a UC San Francisco study released Thursday night, with the toll in 2013 alone running $24.4 billion.

And it’s only getting worse as more people take up cycling. The study found that medical costs from non-fatal bike crashes climbed steadily by $789 million annually, and 3.8 million non-fatal bike injuries in adults were reported over that 17-year period. Nearly 10,000 cyclists died.

“The costs of bicycle injuries have risen steadily since 1997, with a significant increase in emergency department visits and hospital admissions, especially with older men,” wrote lead author Thomas W. Gaither, a UCSF medical student, in the report. “In the past, many bicycle accidents stemmed from non-street incidents. But now, street crashes with motor vehicles represent a greater proportion of the total costs.”

And that was before Seamless, GrubHub and other meal-delivery services that often run on bikes threw even more pedal pushers into the mix in urban areas, where bike accidents are more likely to occur.

“There’s more people on the road biking, so now we’re going to have the potential for more crashes,” Dr. Daniel Cavallo, a family practice and sports medicine physician with CityMD, told Moneyish. “There’s been a big [cycling] push for health. Citibike gives people more access to bicycles … and in New York we’ve seen more people commuting by bike as opposed to taking the subway or a cab.”

There was a 64% increase in the number of Americans cycling to and from work between 2000 and 2012, according to the National Highway Traffic Safety Association – which also saw the number of cyclists killed in motor vehicle crashes rise 12% between 2014 and 2015.

The UCSF study reported a 120% increase in hospital admissions due to bike crashes between 1999 and 2013. City MD, which has 70 urgent care centers across New York, New Jersey and Long Island, has also noticed an uptick in bike injuries.

“We see a lot of concussions, lacerations and abrasions, and the occasional elbow fracture or wrist fracture from falling off the bike,” said Dr. Cavallo. But he credited New York City for lowering the default motor vehicle speed limit to 25 miles per hour on city streets (from 30) and expanding its bike lanes for helping reduce bike vs. car accidents. In fact, cyclist deaths decreased by 21% in NYC in 2015.

UCSF study co-author Benjamin N. Breyer said the report makes a strong case for investing in safer streets. “We can learn lessons from the cycling environment in some European cities, where they have more riders and fewer accidents per rider,” he wrote. “As our cities become more dense and we look for ways to promote active commuting to benefit health and environment, we need to invest long term into our bicycling infrastructure.”