There’s a logic to out-of-pocket medical payments. They’re supposed to make patients think twice before spending money on unnecessary health care.

When it comes to drugs, however, they’re often preventing people from getting necessary care.

A recent data brief from the National Center for Health Statistics said about a quarter of adults who had diagnosed diabetes asked their physician if there was a lower-cost medication they could try, even if things were working for them.

Thirteen percent of them had not taken their medication as prescribed because of the cost.

Some of these patients were uninsured. More than a third of such patients had not taken their medication as prescribed because of the cost; that was also the case for about 18 percent of those with Medicaid. What might be surprising, though, is that 14 percent of patients with private insurance went without their medication as well.

A study in Diabetes Research and Clinical Practice last year examined data on cost-related skipping of diabetes medication. They found that more than 16 percent of those with diabetes engaged in this practice. Those who used insulin and those who earned less than $50,000 per year were more likely to do so.