David Haitkin, a 65-year-old Brooklynite, takes great care to manage his diabetes. Found in his 40s to have Type 1 disease, which requires daily treatment with insulin, he keeps his weight, blood pressure and cholesterol under control, doesn’t smoke and gets daily exercise walking his dog and walking to work.

After checking his fasting blood sugar level every morning, Mr. Haitkin said he administers the appropriate dose of long-acting insulin. He starts his day with a breakfast of oatmeal and eats a regulated amount of mostly complex carbohydrates three times a day “so I don’t end up starved for them.” He relies on healthful fats like olive oil, avocado and nuts, restricts meat portions to four ounces or less and eats fish as often as possible. He also takes the blood pressure drug ramipril to help protect his kidneys, and has his eyes examined and the circulation in his feet and legs checked regularly. He said he’s never had a blood sugar crisis — either a level too high or too low, and so far all body systems seem to be functioning normally.

Then he added a very telling observation: “I’ve always had good health insurance at every job and the luxury to take care of myself. Now though, for a lot of people, that’s being taken away.”

Each of the three diabetes experts I spoke with mentioned insurance problems as a major hindrance for many patients who need to keep their diabetes under control. It is the rare policy that covers consultations for diet and exercise, which can reduce the need for medications and require more time than the 15 or 20 minutes allotted to a doctor visit. But even needed medications are often out of reach financially.

“Having good health insurance is the strongest link to receiving comprehensive diabetes care,” Pooyan Kazemian of Massachusetts General Hospital, the lead author of the new study, told me. “Treatment of diabetes is getting more expensive every day. The newer drugs that control blood sugar with fewer side effects are super expensive, with an average monthly cost of about $1,000, and people without health insurance don’t go to the doctor.”