“There should be forces in society who should be concerned about the budget, about how many M.R.I.s we do, but they shouldn’t be functioning simultaneously as doctors,” said Dr. Martin A. Samuels, the chairman of the neurology department at Brigham and Women’s Hospital in Boston. He said doctors risked losing the trust of patients if they told patients, “I’m not going to do what I think is best for you because I think it’s bad for the health care budget in Massachusetts.”

Image Avastin costs $50 a dose. Credit... Genentech, via Associated Press

Doctors can face some stark trade-offs. Studies have shown, for example, that two drugs are about equally effective in treating an eye disease, macular degeneration. But one costs $50 a dose and the other close to $2,000. Medicare could save hundreds of millions of dollars a year if everyone used the cheaper drug, Avastin, instead of the costlier one, Lucentis.

But the Food and Drug Administration has not approved Avastin for use in the eye, and using it rather than the alternative, Lucentis, might carry an additional, albeit slight, safety risk. Should doctors consider Medicare’s budget in deciding what to use?

Some insurers and state Medicaid programs are now also saying that a highly effective new drug for hepatitis C, Sovaldi, from Gilead Sciences, could lead to an immense increase in spending because so many patients will want to use it, at a cost of $84,000 per course of treatment.

Some of them are hoping that, to save money, only more seriously ill patients will be treated. But Dr. Donald M. Jensen, director of the center for liver diseases at the University of Chicago, said some patients with earlier disease have symptoms like fatigue and would benefit from the drug. “I think ethically we are just worried about the patient in front of us and not trying to save money for the insurance industry per se, or society as a whole,” he said.

Still, some analysts say that there is a role for doctors to play in cost analysis because not many others are doing so.

“In some ways, it represents a failure of wider society to take up the issue,” said Dr. Daniel P. Sulmasy, professor of medicine and ethics at the University of Chicago.