Updated February 29, 2016

If you're like a lot of people with type 2 diabetes, you may not be sure exactly why it's so important to test your blood sugar daily.

In a study published in 2007 in BMJ (British Medical Journal), researchers analyzed the blood glucose monitoring habits of 18 patients with type 2 diabetes over a three year period. At the end of the study, eight out of 18 had developed "monitoring fatigue" and were not testing their blood sugar regularly.

The reason? They weren't sure how to interpret high readings or what to do about them. What's more, they thought their doctor was more focused on hemoglobin A1C and seemed uninterested in the daily blood-sugar results.

In fact, checking your blood sugar daily can:

  • Tell you what to eat next time: Checking blood sugar before and after a meal can determine if the food you're eating is a problem. Rice or corn, for instance, can send blood sugar way up, not just hot fudge sundaes, says Jane Nelson Bolin, PhD, of Texas A&M Health Science Center School of Rural Public Health. The American Diabetes Association suggests a premeal blood-sugar range of 90 mg/dl to 130 mg/dl and a postmeal blood glucose level below 180 mg/dl.
  • Give you a sense of control: Trudy Schoepko, 66, of Albuquerque, N.M., has monitored her blood sugar twice a day religiously since she was diagnosed with type 2 diabetes almost four years ago. "What this whole thing did for me is give me a real sense of there is something in my life I can control, that I have power over it instead of it having power over me."
  • Let you know you're getting sick: Schoepko's blood sugar can also tell her when she's getting sick. Once her blood sugars were in the 190s (very high) and two days later she was diagnosed with pneumonia. Blood sugars rise under stress and during an illness. They can be a sign to take it easy for a few days. "It's a wonderful feedback loop to regulate what I do," Schoepko said.
  • Give a "voice" to a silent disease: "The [blood-sugar] number is really in your face. It's reality, telling you the diabetes is there," said Stuart Weiss, MD, clinical assistant professor of medicine at New York University School of Medicine in New York City. "You can't argue with it all that much."
  • Help you cut your risk of complications: The landmark U.K. Prospective Diabetes Study published in 1998 found controlling blood sugar delays the development of long-term complications including those that affect the eye, the kidney and the nervous system.

Checking your blood sugar regularly can't:

  • Make lifestyle or medication changes for you: If your blood sugar is consistently above 130 mg/dl before meals, or 180 mg/dl after meals, you need to change your diet, exercise level, or medication to lower those numbers.
  • Lower your blood pressure or cholesterol: Even if you do check your blood sugar and adjust what you eat or the medication you take, these measures may not be enough to prevent heart attacks and strokes, the most common cause of death in type 2 diabetes. High blood pressure and cholesterol need to be addressed as well.