They mean well. But you may need to tell people to mind their own business.(ISTOCKPHOTO)

If it hasn't happened yet, it will soon. You'll reach for a treat and a close friend, family member, or even a near-stranger who knows you have diabetes will ask: "Should you be eating that?"

You've just been pulled over by a member of the "diabetes police"—well-meaning citizens concerned about your ability to manage blood sugar on your own.

They probably want to help, but constant nagging about every bit of food you put in your mouth "tends to just work against people with diabetes instead of for them," says Constance Brown-Riggs, a nutritionist and certified diabetes educator in Massapequa, N.Y.

You can try to patiently explainor not

When it happens, you may need to patiently explain that with diabetes you can eat what you want—within reason. As long as you take into account calories and carbohydrate content, and know what the impact will be on your blood sugar, it's OK to eat just about any type of food.

Or you can just tell them to mind their own business.

"It just bombards you all day long. Somebody sees you with a cup. 'What kind of coffee is that? What do you have in your coffee?'" says Deborah, 57, who has type 2 diabetes and lives in New York. "I use Splenda, but I don't have to go around explaining that. People mean well, but you have to ask them to stay back 200 feet."

Tell people how they can really help

Nancy Janow, a 54-year-old librarian who lives in South Orange, N.J., was diagnosed with type 2 diabetes five years ago. Her children, both in their 20s, are often the ones getting on her case.

"My children, especially my daughter, Suzanne, are very, very conscious of my diabetes and my ability to eat certain foods. If I attempt to eat something that's verboten, she'll literally snatch it out of my hands. And I'll get frustrated with that," Janow says.

"I'll say 'Leave me alone.' But it's always 'Mommy, I love you, I want to make sure that you're around.' And that's like the greatest sign of love that I could possibly have. But it doesn't stop me from getting angry," she adds with a laugh, "because I want to eat that cookie."

Some advice, such as "You shouldn't eat that piece of cake," is not that helpful, says William Bornstein, MD, an endocrinologist at the Emory Clinic in Atlanta. It's better if people ask you what you truly need, such as an exercise partner. If they don't ask, initiate the discussion yourself.

"Having a family conversation about what might be helpful is a good thing," Dr. Bornstein says.