Think you don’t have diabetes just because your last blood sugar test said so? Think again! A small but potentially groundbreaking study at Stanford University reveals that annual blood sugar tests—even the vaunted “A1c” test—tell you what’s going on in your body only at the moment you had the test.

That can be a problem because, as the study revealed, your blood sugar actually could be spiking to levels throughout the day that would classify you as one of the 30 million adults in the US with undiagnosed, full-blown type 2 diabetes or as one of the additional 84 million adults with prediabetes, diabetes waiting in the wings.

To better understand spikes in blood sugar levels, the researchers recruited 25 men and 32 women, ages 25 to 76, nearly all with no known prior history of diabetes or prediabetes. Interestingly, as part of their screening for participation, two were found to already have diabetes and 14, prediabetes.

Each participant wore a continuous glucose monitor, or CGM, for up to four weeks. (A CGM system includes a tiny sensor that’s inserted just under the skin on one side of the abdomen, and it checks blood sugar levels every five minutes around the clock, transmitting data wirelessly to a nearby smartphone or receiver.) Blood sugar levels were recorded as study volunteers worked, slept, ate, hung out with friends or cared for their families…in other words, during all their normal day-to-day activities.

Some of the results were startling. Many participants who did not have diabetes based on initial screening experienced frequent blood sugar surges that put them into the prediabetic or even the diabetic range. The researchers also noted that blood sugar ranges were much higher in some participants than in others in response to specific foods. Other studies have shown that over time, high glucose spikes in people can damage organs including the pancreas, liver and heart.


While a CGM is traditionally recommended for people with diabetes as an alternative to frequent finger pricks to track blood sugar, for people without diabetes, wearing the device once a year may be a great way to see whether you’re in the danger zone for developing the disease, says study coauthor Michael Snyder, PhD. For your first time, you might wear the sensor for three or four weeks, he says, while keeping a journal of everything you eat and noting which foods trigger spikes. By cutting back on these foods, it may be that you can help delay or even prevent the onset of full-blown diabetes. In successive years, wearing a CGM for just one week would enable you to catch any changes and make any needed adjustments, says Dr. Snyder.

To get started, you’ll need to ask your doctor for a CGM prescription, instructions on how to use it (it causes only a brief sting as the sensor is inserted) and a follow-up appointment to discuss the readings. You might be met with skepticism at first, but this example of personalized medicine can give you far greater insights into your health than a single test and offer the opportunity to prevent a lifelong condition that comes with serious complications, including heart disease. While insurance won’t pay for a CGM for someone without diabetes, Dr. Snyder believes that these devices will soon become inexpensive and direct-to-consumer, giving people easy access to monitoring their glucose levels.

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