You depend on your doctor to help you understand your health and identify medical problems that arise.

While your physician probably does her best, no one is perfect. What happens when your doctor misses something or just plain gets it wrong? A new overview study by researchers from Baylor University and the University of Texas shows diagnostic errors occur in doctors’ offices and clinics more often than you might think.

After reviewing several studies analyzing adult care in these settings, the scientists came up with an overall rate of diagnostic mistakes: 5 percent. Apply that to the adult population of the United States and you have an estimated 12 million people each year who are the subject of an incorrect or missed diagnosis in an outpatient setting … meaning one that does not involve an overnight hospital stay.

The studies did not include pediatricians and their patients, but it’s safe to say slip-ups happen there, too. That means there are probably many more diagnostic errors each year.

About half of the mistakes were minor, but some included multiple failures to diagnose colon cancer or lung cancer, despite test results that showed evidence of these diseases.

But we all know many health woes that start out small can grow dangerous if left unchecked. Sometimes, taking medication or undergoing a procedure based on a diagnostic error can put patients at risk of additional problems. The study authors estimated that about half of all diagnostic errors could harm patients.

Understanding the scope of mistakes in this arena of medicine is key to improving the nation’s health care and decreasing costs. There are many programs aimed at bettering care at American hospitals, but that’s not the only place we should focus.