Several years ago, I saw a woman with unexpectedly high blood pressure. Her readings were as high as 140/110, way above the normal value of 120/80. Though she was otherwise healthy, she was at risk of a stroke.

Because extreme hypertension in young women can be caused a blockage of an artery to the kidney, I scheduled an M.R.I. within in a few weeks. But she never had the test or followed up with me.

Patients frequently miss appointments and tests that their doctors schedule. No-show rates range from 5 to 55 percent. In some instances, like when a patient skips a cardiac stress test, for example, then has a heart attack, the hospital might classify what occurred as a “systems error.” Ideally, such cases lead to new policies that prevent similar events.

But what about less drastic cases, in which follow-up is necessary but not an emergency? Should patients be held responsible for not showing up? Or does the medical profession have an ethical and legal duty to try to track down the individuals?

Patients miss appointments for many reasons. Some simply forget or get confused. Others may have conflicts. If they promptly reschedule, there is no problem. But many do not or, when they call the doctor’s office, cannot get a prompt new appointment.

When I schedule tests and follow-up visits, I expect that they will occur. As such, one might assume that there are foolproof systems in place to ensure follow-up. Yet this is far from the case.

From a legal perspective, rescheduling needs to occur. “Medical liability experts,” according to an article in American Medical News, “say missed appointments and failures to follow up pose some of the greatest legal risks for physicians.” But putting a system into place for following up with absent patients is expensive and time-consuming at a time when many physicians’ offices and hospital clinics are just trying to stay afloat.

Fortunately, experts are devising systems to expedite follow-up. For example, a family medicine clinic at the University of Wisconsin lowered no-show rates from 33 to 18 percent by interviewing no-show patients, implementing a new scheduling process and double-booking the number of slots that corresponded to its no-show rate. Other effective techniques included making reminder calls before an appointment, reducing wait times and creating a more welcoming environment.

From an ethical perspective, things are hazier. Do patients really have no responsibility when it comes to follow-up? After all, non-adherence by patients is a well-known and inevitable phenomenon. If one argues that doctors or their colleagues need to call all people who miss appointments, why shouldn’t we also be calling every day to make sure patients are taking their medications, exercising or adhering to their diets?

Certain patients surely require special attention: non-English speakers, persons with dementia or other neurological conditions and those with social problems that interfere with their ability to show up. Doctors’ offices should anticipate these types of issues and work with patients to improve compliance.

But there is a limit to what can be done. For example, many of the patients I treat at Bellevue Medical Center do not have stable addresses or working phones. And, realistically, my colleagues and I already work late, trying to squeeze in more and more patients as reimbursements go down. Do we have an ethical duty to hire additional staff members to call “missing” patients? Or should we do so ourselves after we get home from work or on the weekends? Indeed, physicians may even secretly hope for a few absentees, which enable them to spend extra time with the patients who do show up.

One thing experts agree on is improved documentation. If a doctor schedules a test or appointment for a patient that is particularly important, he or she should document having emphasized this issue with the patient. While this is not a foolproof method for preventing lawsuits, it helps to clarify the physician’s performance and line of thinking about the case.

Even when a clinic staff member calls patients in advance, my no-show rate still hovers from 10 to 20 percent. If the visits are for checkups, I do not routinely call the patients, but if there are urgent matters to be discussed, I do. Some of my patients have received delayed care because of missed visits, although thankfully there have been no serious outcomes (that I know of). But the chance is always there.

So what did I do when my patient with hypertension seemingly disappeared? I called the number in the computer. The person who answered told me that she had unexpectedly moved back to her native country, in Africa.

So I did what I could. I told him to contact the woman and urge her to get prompt diagnosis and treatment either there or here. I said her condition was potentially dangerous. He promised to pass along the message.

And then I wrote a note documenting the conversation.

Originally published in the “Well” blog of the New York Times, November 13, 2014