Finger-stick monitors have long been the only way for people with diabetes to determine their glucose levels on a day-to-day basis. Anywhere from twice a week to several times a day, patients jab their fingers with small lancet needles to draw drops of blood that can then be slipped into a monitor to measure the concentration of the glucose in their blood. Aside from the pain and inconvenience, such occasional blood sampling is less than ideal for maintaining healthy glucose levels.

But the era of lancet pricks may be coming to an end. In the past few years, three companies—Medtronic Diabetes, DexCom and Abbott Diabetes Care—have introduced the first personal continuous glucose-monitoring devices, a new technology that relies on a sensor implanted underneath the skin to send information on glucose levels via a radio transmitter to a pager-size monitoring device. These gadgets are not yet a permanent solution for glucose monitoring: the FDA has only approved sensors that measure continuously for three to seven days, when the sensors have to be replaced.

Still, continuous glucose monitors are allowing patients to access a previously unimaginable amount of information about their bodies. The tiny rechargeable, waterproof sensor on Medtronic’s Real-Time continuous glucose monitor, for example, sends measurements to the monitor every minute. The device then displays an average of the last five minutes’ worth of data. In total, it generates some 288 readings every day—almost 100 times as many as patients using a traditional monitor. The device provides readings of daily glucose highs and lows, and it also integrates trends in the data, which can then be downloaded onto a computer. This minute-by-minute catalogue allows users to see exactly how certain foods and activities affect their bodies. Medtronic also offers a version of the device that interacts with its insulin pump, which displays information from the sensor, allowing users to adjust insulin levels more conveniently.

While these devices offer a glimpse into an exciting future—eventually the monitors may be able to automatically adjust insulin pump doses, operating as a kind of mechanical pancreas—a few major obstacles remain in the short term. For one thing, continuous glucose monitors are not automatically covered by insurance unless a patient shows a specific need. Subcutaneous sensors also have their drawbacks. Because they are implanted in tissue underneath the skin and not in the bloodstream itself, they don’t always register the exact glucose levels in the body. Subcutaneous glucose levels tend to lag those in the bloodstream, making calibration a problem. To avoid this discrepancy, Abbott’s device, the Navigator, doesn’t allow itself to be calibrated if glucose levels are rising. Abbott’s monitor is the only one of the three companies’ devices that has not yet received FDA approval, although it is expected later this year.     —Justin Ewers