Glucose monitoring systems that continuously plot the course of blood glucose promise much greater control over blood glucose levels. Detecting when you are going low is just one benefit, but it is the most immediate reward.

Eighteen companies have announced that they have developed or are working on continuous-sensing meters.

Medtronic MiniMed already has continuous glucose-monitoring systems on the market, but currently they require users to visit a doctor’s office to learn what their levels were.

Soon, another continuous-sensing system may be available—the FreeStyle FreeStyle Navigator Continuous Glucose Monitor.

TheraSense, Inc., in Alameda, California, submitted a pre-market approval application (PMA) to the U.S. Food and Drug Administration in late 2003. Meanwhile, Abbott Laboratories in Abbott Park, Illinois, purchased TheraSense to complement its MediSense glucose meter business. The resulting company, Abbott Diabetes Care, is headquartered in Alameda.

Abbott has asked the FDA to approve the device as a replacement for a blood glucose meter, something never done before. Other systems have been approved only as a secondary source of glucose information, and it was still necessary to continue using a traditional glucose meter.

The FreeStyle Navigator will use a disposable miniaturized electrochemical sensor that the user can easily insert under the skin of the abdomen, upper arm or elsewhere with a spring-loaded insertion device. The sensor, which measures interstitial fluid, is inserted 5 to 6 millimeters below the skin and at a 90-degree angle. It wirelessly transmits to a device that can be carried in a pocket or purse and can sit on the nightstand at night.

The company’s published papers show a lag-time variation from capillary blood glucose levels of between 5 and 12 minutes. This is not a problem, however, because there are new data every minute.

The FreeStyle Navigator is designed to help detect a low even during sleep, but it will also warn users of dangerous high levels. Just as important are the trends that it will detect, helping users to correlate their food intake, activity levels, and the amount and timing of insulin or oral medication with blood glucose levels.

The FreeStyle Navigator won’t abolish blood glucose lows and highs, but it certainly promises to help control them.

Welcome Back, Sleep Sentry

Another way to be aware of lows is to monitor the typical symptoms of hypoglycemia: excessive perspiration and a drop in skin temperature. The Sleep Sentry, worn like a wristwatch, sets off an alarm when it detects either or both of these symptoms. However, not everyone exhibits these two symptoms that are needed to trigger the alarm.

“When the alarm sounds, users always should test their blood glucose to determine whether they are having a hypo[glycemic episode],” says Marv Meier, president and CEO of Diabetes Sentry Products in Bellingham, Washington. “It doesn’t cause any irritation or discomfort when you use it, so people are more apt to use it routinely.” The Sleep Sentry sells for $389. There are no ongoing costs other than changing the batteries every six months or so. To learn more, see the Web site at http://sleepsentry.com.