PITTSBURGH (KABC) -- Antibiotics can be life-saving, but overuse is leading to a real problem called antibiotic resistance.
It happens when bacteria change to resist the effects of the medicine.
"People have to remember that bacteria have been on this earth for 4 billion years, so it's not a surprise that bacteria are able to outwit us," said University of Pittsburgh's Dr. Amesh Adalja.
Experts believe about one-third of antibiotics prescribed in the U.S. are unnecessary. A new report encompassing 76 countries found antibiotic use increased 39 percent between 2000-15.
Researchers predict that if nothing changes, up to 10 million deaths worldwide may be attributed to antibiotic resistance by 2050.
"We're running out of antibiotics and we're now left in certain scenarios with telling a patient that we have nothing to offer them," Adalja said.
Doctors advise patients not to stop taking an antibiotic early if it's prescribed. Doing so makes it easier for bacteria to replicate and become resistant.
It's also inadvisable to use leftover antibiotics as those can increase resistance as well.
"One of the primary drivers, at least in this country, is the fact that the public begins to demand antibiotics for any cough, cold or viral illness, irrespective of the fact that antibiotics have no effect on viruses," Adalja said.
In fact, taking antibiotics for a viral infection may do more harm than good.
Antibiotic resistance increasing worldwide, doctors say