Still, not everyone is on board. Critics of this most recent trial said it didn’t prove that blood glucose monitoring couldn’t help: It’s possible that with better training, or more attention to detail, there might be ways to make this work.

The point of pragmatic comparative effectiveness trials like this, though, is to test how practices work in the real world. In these high-quality primary care practices, even with customized help in interpreting the measurements (which is more than most patients get), testing blood sugar didn’t make a difference.

Choosing Wisely, an educational campaign aiming to reduce unnecessary medical tests and procedures, advises against routine home glucose monitoring for patients with Type 2 diabetes who are not on insulin. It says there is no benefit, and that there are potential harms (a study has shown an association with increased anxiety and depression). This argument is supported by the American Academy of Family Physicians, the Society of General Internal Medicine and the Endocrine Society.

Of course, there are exceptions. When patients are acutely ill, or changing regimens, or finding that their blood sugar is not well controlled, testing may be appropriate. Such decisions should be made in consultation with a physician.

But for most people with Type 2 diabetes not on insulin, testing is inappropriate most of the time. That message is not getting through. At the end of last year, another study was published in JAMA Internal Medicine that quantified the prevalence of glucose testing in adults. Researchers examined a database that contained data on more than 370,000 commercial health insurance and Medicare Advantage beneficiaries who had Type 2 diabetes.

Of the more than 23 percent of patients who were using testing strips, more than half were probably doing so in spite of widespread recommendations that they shouldn’t. They were using a median of two testing strips a day at a cost of more than $325 per year per patient.

On another front, The New York Times has reported that “a surprisingly large number of people” who use insulin are using less because they can’t afford it, putting themselves in danger.

With a health care system as complicated as ours, it’s hard to take money from one pot and shift it easily to another. Efficiency in each system is crucial. The fact that a necessary facet of diabetes care is increasingly out of reach — while unnecessary and potentially harmful care is easily overused — illustrates how much work still needs to be done.