To many consumers, opening an envelope with a medical bill is a little too much like playing the lottery in reverse.

It feels like a random drawing — of how much you’re going to pay.

The seeming arbitrariness of medical expenses has vexed policymakers for decades, adding to the complexity and opacity of the health care system. For individual consumers, that variation can hit them right in the wallet. A state commission that completed its work on Wednesday even gave the phenomenon a name: surprise billing.

“Everybody, whether it’s happened to a family member or to them, can relate to this kind of situation happening,’’ said state Senator James T. Welch of Springfield, the commission’s co-chair.

Surprise bills can snag even the most cost-conscious consumer. That’s because the prices charged for medical procedures vary according to a mind-numbing list of factors, many of which are difficult for a nonspecialist to anticipate. A patient might go to an in-network hospital for surgery, expecting to pay in-network rates, only to open the bill later and find that the hospital used an expensive out-of-network anesthesiologist.

And that’s to say nothing of emergency patients who can’t realistically shop around for their medical care. One can’t always break an arm near an in-network provider.

The 23-member commission, drawn from hospitals, insurers, labor, and the business community, was created to study price variation more broadly, and especially the different rates insurers pay to providers for the same procedure. It produced some valuable recommendations to reduce those disparities, which tend to hurt community hospitals that serve the neediest patients but often receive less than downtown teaching hospitals. But by calling attention to surprise billing, and offering some solutions, the panel also put a welcome consumer protection reform on the table.

While it leaves many details up to the Legislature, the commission suggested requiring more transparency from providers. California, Connecticut, and New York, the commission notes, have taken steps to ensure patients are warned before they are cared for by a nonparticipating provider.

But the report also recognizes that transparency has limits as a solution to all that ails the health care system. It recommends a ban on balance billing in emergency situations. And it suggests setting some form of standard default price for out-of-network charges based on average prices — limiting how much that out-of-network anesthesiologist could charge.

State Representative Jeffrey Sanchez of Jamaica Plain, the commission’s other co-chair, said there was still work to be done fleshing out the proposal, and more stakeholders to consult, including emergency room doctors, before the Legislature could act on the recommendations. But, he said, “we’re on the glidepath to agreement on this issue.’’ A consensus sometimes seems rare in health care policy — which is all the more reason for lawmakers to act now that they’ve found one.