NEW YORK — Almost half of hospital doctors said they routinely see more patients than they can safely manage, leading in some cases to unneeded tests, medication errors and deaths, according to a survey by researchers at Johns Hopkins University.

Seven percent of 506 hospital-based physicians surveyed said their heavy workload likely led to a patient complication, and 5 percent reported it probably caused a death over the past year. The findings are published in a research letter released Monday by JAMA Internal Medicine.

Doctors are increasingly taking on more patients to compensate for cuts in payments from health insurers, the researchers said. That workload is projected to increase as the 2010 health law expands insurance coverage to 30 million more Americans. The researchers, based at Johns Hopkins University in Baltimore, said there is a risk that rising patient volumes may increase costs by decreasing quality.

“Excessively increasing the workload may lead to suboptimal care and less direct patient care time, which may paradoxically increase, rather than decrease costs,” the study’s authors wrote.

Forty percent of doctors said they saw an unsafe number of patients at least once a month with 25 percent saying it prevented them from fully discussing treatment options or answering questions, according to the survey.

Researchers electronically surveyed doctors in November 2010 using a physician networking website. The average age of the physicians was 38 with an average salary of $180,000. Doctors said they could safely manage 15 people during a shift if they were able to devote 100 percent of their time to patient care.

Lawmakers have moved to prevent medical errors by putting restrictions on the number of hours doctors in training can work and set standards for nursing staffing levels. There are no similar limits on workloads for physicians who focus primarily on care of hospitalized patients.