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Diabetes Health Center

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How Does a Continuous Glucose Monitor Work?

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Glucose meters are a great tool, but sometimes you need to keep a closer eye on your blood sugar levels. That's where a device called a continuous glucose monitor (CGM) can help. This FDA-approved system tracks your blood sugar levels day and night. It collects readings automatically every 5 minutes.

Along with your finger sticks, it can help detect trends and patterns that give you and your doctor a more complete picture of your diabetes. The data can help you find ways to better manage your condition.

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Several devices are available for adults and children. You need a prescription from your doctor to get one.

What Does It Do?

CGM uses a tiny sensor placed under the skin of your belly. You can put it in quickly, and it’s usually not painful. It measures the amount of glucose in the fluid inside your body. A transmitter on the sensor then sends the information to a wireless-pager-like monitor that you can clip on your belt.

The monitor displays your sugar levels at 1-, 5- and 10-minute intervals. If your sugar drops to a dangerously low level or a high preset level, the monitor will sound an alarm.

In the past, only doctors could see the readings CGM systems collected. Now anyone can use the devices as part of at-home diabetes care. You can download data on your computer, tablet, or smartphone to see patterns and trends in your sugar levels. The information can help you and your doctor make the best plan for managing your diabetes, including:

  • How much insulin you should take
  • An exercise plan that’s right for you
  • The number of meals and snacks you need each day
  • The correct types and doses of medications

CGM doesn’t replace traditional home monitors or the need for finger sticks. You’ll still need to measure your blood sugar with a regular glucose meter a few times a day to help the monitor stay accurate. You should also replace the sensor under your skin every 3 to 7 days.

If you use an insulin pump, you can also link it to your CGM system for continuous care. You won’t need to manually program the pump as with the other finger-prick methods. This is called a “sensor-augmented pump.”

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