After Kim Lauerman’s ovarian cancer was diagnosed, doctors wanted to give her a drug that helps prevent infections and fever during chemotherapy. Her insurer said no.

Anthem Blue Cross said the drug wasn’t necessary. She eventually got it after an infection landed her in the hospital and she ended up missing several chemo sessions.

“The insurance has been great until I got to a point that I really needed something for survival,” Lauerman said.

Doctors say they worry about the growing influence insurers have over patient care. Some are finding they need more insurance approvals for routine things like medical scans or some prescriptions, which can postpone care for days or weeks.

Insurers say medical advances are prompting them to review more cases before deciding on coverage. They say the checks are not meant to delay or stifle care, and they see them as a way to guard against unnecessary treatment. “It’s not the end of the conversation,” said Kristine Grow, a spokeswoman for the insurer trade group America’s Health Insurance Plans.

In the middle are patients who face treatment interruptions, which can stir anxiety and, in some cases, influence the success of their care.

Lauerman, 57, of Alpharetta, Ga., said she worries her advanced cancer may return because her treatment was cut short. Doctors wanted her to get chemotherapy and the drug Neupogen to boost infection-fighting white blood cells. But they had to end chemo early after she developed an infection.

Federal privacy laws prevent Anthem from commenting on Lauerman’s case. But spokeswoman Lori McLaughlin said the insurer covers Neupogen. That decision can depend on the patient’s health, the treatment plan and guidelines from cancer groups, she said.

No independent research tracks how frequently insurance issues delay or curtail care, but doctors say they’ve seen a marked increase in difficulties in the past few years.

Dr. Ray Page of Fort Worth, Texas, said more than 90% of his patients need an insurer’s approval before he does a positron emission tomography scan to try to figure out where cancer has spread. He said his patients rarely had to wait for such approvals five years ago.

“That patient is putting their life in my hands, and they need to be able to trust me,” he said. “When you have these outside interferences telling me I can do this and I can’t do that … that very quickly erodes the trust.”

Dr. Barbara McAneny said insurer-created delays have become common in many types of cancer care, including for pain medication. “When patients have chronic pain and you make them go without their pain medication for several days … waiting for the wheels of insurance companies to turn, it is cruel,” said McAneny, an Albuquerque-based oncologist and former president of the American Medical Association.

Outside cancer care, doctors say coverage for routine tests like MRIs has become difficult. Autoworker Lance Hopkins lived with radiating neck pain for weeks while he awaited insurance approval of an MRI. The 55-year-old of Monson, Mass., said his doctor needed the exam to find a suspected pinched nerve, but his insurer only approved less precise tests.

“What really stunk is my granddaughter had a fishing derby and I couldn’t even hold a fishing pole to help her,” he said. “All I could do is sit there and watch.”

Insurers base their decisions on treatment guidelines established by medical societies, said Dr. Michael Sherman, chief medical officer for Harvard Pilgrim, which offers employer-sponsored and individual coverage.

They have to guard against such problems as addiction to pain medications, radiation exposure or unscrupulous doctors who have their own imaging devices and want to make money. They also try to rein in costs.

“If we can’t do that, and we see premiums continue to go up … people won’t be able to afford insurance, let alone health care,” Sherman said.