Drones have proven they can deliver 7-Eleven Slurpees to thirsty customers and navigate high-speed racetracks for our entertainment. But can they save lives?

Half Moon Bay drone startup Zipline recently announced it raised $25 million from major investors to deliver blood to transfusion patients in Africa.

“The inability to deliver life-saving medicines to the people who need them the most causes millions of preventable deaths each year,” CEO Keller Rinaudo wrote in a news release. “Zipline will help solve that problem once and for all.”

Zipline began dropping blood in Rwanda, and plans to ramp up to between 50 and 150 on-demand deliveries a day to 21 local transfusion clinics. Zipline’s latest round of funding, provided by Sequoia Capital, Andreessen Horowitz and other investors, will allow the startup to expand its flights to other countries throughout Africa, according to the release. Within the next six months, Zipline also hopes to begin making deliveries within the U.S., in collaboration with the White House and the FAA. The company also intends to expand its delivery beyond blood, eventually dropping medicine and vaccines.

Zipline’s business model attacks the “last-mile problem” — lack of transportation and communication often makes it difficult to get blood or medicine from a city to a rural or remote area. In Rwanda, the company is focused on supplying blood to women suffering from postpartum hemorrhaging. Clinics in need can place an emergency order by text message, which will be filled with an on-demand drone drop. Drones are an ideal way to deliver the needed blood, Zipline says, because blood spoils quickly, many clinics cannot store enough blood to meet their needs, and long rainy seasons that wash out Rwanda’s roads make transportation by car or truck difficult.

Including its most recent round of funding, Zipline has raised $43 million.