Most U.S. doctors are quietly using this AI tool. Few patients know about it. - NBC News

Your doctor is probably using AI, even if they haven’t told you about it.

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Over the past two years, medical providers across America have quietly embraced a new AI tool called OpenEvidence to help them make clinical decisions, brush up on medical knowledge and even prepare for their licensing exams. The service, a sort of chatbot for doctors, was used by about 65% of U.S. doctors across almost 27 million clinical encounters in April alone, the company told NBC News.

“Everyone is using it,” said Dr. Anupam Jena, an internal medicine physician at Massachusetts General Hospital in Boston and a professor of healthcare policy at Harvard. “Its growth really has been exponential.”

NBC News spoke with over two dozen doctors, hospital administrators, medical students and healthcare researchers from Hawaii to Maine to explore the rise of OpenEvidence. Each individual said they either used it regularly themselves or knew someone who did.

Almost two-thirds of physicians — or roughly 650,000 doctors — in the U.S. actively use OpenEvidence, while another 1.2 million use it internationally, OpenEvidence representatives said. With its quick and tailored replies, OpenEvidence has become an AI-era equivalent of consulting a colleague for their expert opinion, though the software can also write patient discharge notes and provide custom study tools for doctors’ medical exams.

“Sixty percent of all the searches are about how to make clinical decisions,” said Jena, who is currently examining 90 million OpenEvidence queries submitted since 2024 as part of a new research project. “The physicians are asking: For this particular patient, or with this profile, this condition, maybe other comorbidities that they have, what’s the right treatment?”

Yet with OpenEvidence’s skyrocketing popularity, some experts worry about potential hallucinations or incomplete answers, a lack of rigorous scientific studies on the tool’s patient impact, and the potential for doctors’ critical thinking and evaluation skills to erode with increased OpenEvidence use and dependence.

But many in the medical world see OpenEvidence as a time-saving tool that can improve patient care.

Do you have a story to share about AI in medicine or other professions? Contact reporter Jared Perlo.

“The vast majority of our physicians are familiar with it, depending on their area of specialty,” said Dr. Jeremy Cauwels, a hospitalist and the chief medical officer for the Sanford Health system based in Sioux Falls, South Dakota.

“OpenEvidence is one of those tools that’s remarkably easy to adopt,” said Cauwels, who oversees more than 2,500 healthcare providers in the country’s largest rural healthcare system. “It’s freely available, it’s very functional on your phone, and it’s one of those things that can help you answer questions more quickly than you would be able to by any other method.”

Doctors across specialties, states and clinic sizes echoed the sentiment.

For example, a junior doctor at a New Hampshire hospital said that when he saw a patient’s potassium value plummet, he checked OpenEvidence to make sure it was a normal side effect of a medication and not a new emergency. After searching through peer-reviewed medical publications, OpenEvidence said it was a common side effect and provided several options to restore normal potassium levels.

Meanwhile, across the country, a doctor at an Indian Health Service medical center in rural South Dakota was not convinced a patient’s spine was fractured after looking at specks on an X-ray. He vaguely recalled from his medical school training that a different type of scan might be needed to make a firm diagnosis, so he asked OpenEvidence whether an X-ray would suffice. OpenEvidence said that a CT scan was preferred to confirm that type of fracture and provided several links to papers with more information. Both doctors requested anonymity because their employers had not authorized them to speak to the press.