If you knew you were going to be admitted to the hospital for a serious and unexpected medical problem, which day of the week would you pick?

It sounds like a silly question. You don’t get to pick the day you will become sick, of course. It’s unexpected. And why should it make a difference? Isn’t a hospital with a 24 hour nursing staff and on call physicians the safest place you can be? Not always.

Patients hospitalized Friday night or over the weekend stay longer than patients admitted for the same problems Monday through Thursday. This adds unnecessary costs to their medical treatment. But the problem is more than financial. These patients also face a greater chance of experiencing a complication. And the extra day can even cost patients their lives. It’s a risk that most people don’t realize and most doctors don’t acknowledge.

A Journal of the American Medical Association study found that hospitalized patients who suffered a cardiac arrest during nights and weekends were less likely to survive. A British study found that patients who were admitted to a hospital on a Sunday faced a 16 percent higher risk of dying within a month than those admitted on weekdays. And Canadian scientists found that ischemic stroke sufferers admitted to hospitals over the weekend were more likely to die within seven days than those admitted during the week.

The obvious question here is: Why? The answer is a complicated mix of economics and medical culture.

During the week, all diagnostic and interventional services are open. On the weekend, many of them shut down except when staff members are called in to care for a life-threatening problem. The on call staff understands that when a patient’s life depends on their expertise, they need to stop what they are doing and drive to the hospital. But the culture of medicine supposes that making a stable patient wait until Monday won’t be a problem.

As a result, the pace of medical care for patients on the weekend slows from a run to a walk. On Saturdays and Sundays, many stable patients “hang out” in hospital beds. Therefore, it takes more time to determine their diagnosis and treat them. It seems innocuous. But for some patients, waiting until Monday morning allows their disease to progress. And each passing day increases the likelihood that a patient will experience a hospital-acquired infection or medication error.

There is also the risk of delirium — sudden and severe confusion. Hospitals are continuously noisy and bright, and an added night of sleep disruption can induce delirium, requiring on average three extra days in the hospital and up to six months to recover fully.

No matter the reasons, the waiting game has proven dangerous and costly. So, what can be done about it?

Studies like the ones referenced earlier make it clear that what some call the “weekend effect” can be harmful to patients. But the studies don’t provide proven solutions. Here are a few things we at Kaiser Permanente have learned can be done to decrease the added risk of a weekend hospital stay.

Most hospitals provide sophisticated diagnostic testing and interventional procedures for two groups of patients: those staying in the hospital overnight and those being treated on an outpatient basis. These less urgent outpatient studies and procedures are typically scheduled Monday to Friday.

In contrast, the weekends are unscheduled with technical staff and doctors are only made available should an emergency arise. By scheduling some of the weekday patients on the weekends and spreading out the staffing over seven days, the necessary teams are available every day to provide rapid care to these less urgent inpatients. Even though their medical problems are stable, the sooner these patients are diagnosed and the more rapidly they are treated, the faster they can recover and the lower the risk of complications.

The lack of clinical services on the weekends is not the only thing that causes a problem.

Physicians tend to come to the hospital later in the day on weekends. And the coordination of care that happens on weekdays diminishes on Saturday and Sunday. Solving this requires bringing all of the specialty consultants together and achieving consensus on when they will begin their morning rounds: seven days a week. And on weekends, physicians often wait until the next morning to check on the results of the tests they ordered earlier in the day. Making certain that follow up is completed each afternoon, whether by that individual or a colleague, speeds up the healing process.

It’s no surprise that having more doctors and technicians on hand over the weekend improves patient outcomes. And maximizing the performance of high capital facilities seven days a week isn’t new to business leaders. But making this change in expectations will clash with medical culture.

Expanding weekend hours and raising expectations will impact the lives of physicians and staff in ways they are likely to resist. But with reduced payments from Medicare and increasing demands for lower prices through the health insurance exchanges, expectations are going to change.

Since these agreements will be inconvenient for people, the hospital could provide financial incentives to physicians and staff for improved quality outcomes to ensure the changes are being carried out effectively and collaboratively.

And once hospitals change their practices, the real winners will be patients and their families.

Robert Pearl is a physician and CEO, The Permanente Medical Group. This article originally appeared on Forbes.com.