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Continuous Glucose Monitoring

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What is glucose monitoring?

Glucose monitoring helps people with diabetes manage the disease and avoid its associated problems. A person can use the results of glucose monitoring to make decisions about food, physical activity, and medications. The most common way to check glucose levels involves pricking a fingertip with an automatic lancing device to obtain a blood sample and then using a glucose meter to measure the blood sample's glucose level.

Drawing of a glucose meter and a person using a lancing device to obtain a blood sample from a fingertip for testing with the meter.
People with diabetes typically use a lancing device to obtain a blood sample and a glucose meter to measure the glucose level in the sample.

Many types of glucose meters are available, and all are accurate and reliable if used properly. See the American Diabetes Association's annual resource guide at www.forecast.diabetes.org Exit Disclaimer image for more information. Some meters use a blood sample from a less sensitive area than the fingertip, such as the upper arm, forearm, or thigh.

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What is continuous glucose monitoring?

Continuous glucose monitoring (CGM) systems use a tiny sensor inserted under the skin to check glucose levels in tissue fluid. The sensor stays in place for several days to a week and then must be replaced. A transmitter sends information about glucose levels via radio waves from the sensor to a pagerlike wireless monitor. The user must check blood samples with a glucose meter to program the devices. Because currently approved CGM devices are not as accurate and reliable as standard blood glucose meters, users should confirm glucose levels with a meter before making a change in treatment.

Drawing of three people, each using a different type of wireless continuous glucose monitoring system. A man on the left wears a glucose sensor/transmitter on his right arm and holds a monitor in his left hand. In the middle drawing, a woman's torso is shown with a sensor/transmitter attached to her abdomen and a monitor attached to her clothing. A woman on the right wears a third type of monitor outside her clothing; the sensor/transmitter is worn beneath her clothing so it is not pictured.
CGM systems provide glucose measurements as often as once per minute. The measurements are transmitted to a wireless monitor.

CGM systems are more expensive than conventional glucose monitoring, but they may enable better glucose control. CGM devices produced by Abbott, DexCom, and Medtronic have been approved by the U.S. Food and Drug Administration (FDA) and are available by prescription. These devices provide real-time measurements of glucose levels, with glucose levels displayed at 5-minute or 1-minute intervals. Users can set alarms to alert them when glucose levels are too low or too high. Special software is available to download data from the devices to a computer for tracking and analysis of patterns and trends, and the systems can display trend graphs on the monitor screen.

Additional CGM devices are being developed and tested. To learn more about such monitors and new products after approval, call the FDA at 1-888-INFO-FDA (463-6332) or at www.fda.gov/MedicalDevices/default.htm.

Drawing of a woman sitting at a desk and looking at a chart of glucose levels on a computer screen.
People who use CGM systems can download data to a computer to see patterns and trends in their glucose levels.

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What are the prospects for an artificial pancreas?

To overcome the limitations of current insulin therapy, researchers have long sought to link glucose monitoring and insulin delivery by developing an artificial pancreas. An artificial pancreas is a system that will mimic, as closely as possible, the way a healthy pancreas detects changes in blood glucose levels and responds automatically to secrete appropriate amounts of insulin. Although not a cure, an artificial pancreas has the potential to significantly improve diabetes care and management and to reduce the burden of monitoring and managing blood glucose.

An artificial pancreas based on mechanical devices requires at least three components:

  • a CGM system
  • an insulin delivery system
  • a computer program that "closes the loop" by adjusting insulin delivery based on changes in glucose levels

With recent technological advances, the first steps have been taken toward closing the loop. The first pairing of a CGM system with an insulin pump—the MiniMed Paradigm REAL-Time System—is not an artificial pancreas, but it does represent the first step in joining glucose monitoring and insulin delivery systems using the most advanced technology available.

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Points to Remember

  • Glucose monitoring helps people with diabetes manage the disease and avoid its associated problems.
  • The most common way to check glucose levels involves pricking a fingertip to obtain a blood sample and using a glucose meter to measure the glucose level in the sample.
  • Continuous glucose monitoring (CGM) systems use a tiny sensor inserted under the skin to check glucose levels in tissue fluid. A transmitter sends glucose measurements to a wireless monitor.
  • An artificial pancreas based on mechanical devices will consist of a CGM system, an insulin delivery system, and a computer program to adjust insulin delivery based on changes in glucose levels.

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Hope through Research

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and the National Institutes of Health (NIH) have encouraged and supported research that has helped researchers explore and develop improved glucose sensing technologies. NIDDK support was instrumental in the development of two CGM devices. One device is on the market and the other is under review by the FDA. Research supported by the NIDDK and NIH is contributing to the development of an artificial pancreas that will combine continuous glucose sensing with insulin delivery in a "closed-loop" system.

Participants in clinical trials can play a more active role in their own health care, gain access to new research treatments before they are widely available, and help others by contributing to medical research. For information about current studies, visit www.ClinicalTrials.gov.

The U.S. Government does not endorse or favor any specific commercial product or company. Trade, proprietary, or company names appearing in this document are used only because they are considered necessary in the context of the information provided. If a product is not mentioned, the omission does not mean or imply that the product is unsatisfactory.

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For More Information

National Diabetes Education Program
1 Diabetes Way
Bethesda, MD 20814-9692
Phone: 1-888-693-NDEP (6337)
TTY: 1-866-569-1162
Fax: 703-738-4929
Email: ndep@mail.nih.gov
Internet: www.ndep.nih.gov

American Diabetes Association
1701 North Beauregard Street
Alexandria, VA 22311
Phone: 1-800-DIABETES (342-2383)
Email: AskADA@diabetes.org
Internet: www.diabetes.org Exit Disclaimer image

Juvenile Diabetes Research Foundation International
26 Broadway, 14th Floor
New York, NY 10004
Phone: 1-800-533-CURE (2873)
Fax: 212-785-9595
Email: info@jdrf.org
Internet: www.jdrf.org Exit Disclaimer image

You may also find additional information about this topic by visiting MedlinePlus at www.medlineplus.gov.

This publication may contain information about medications. When prepared, this publication included the most current information available. For updates or for questions about any medications, contact the U.S. Food and Drug Administration toll-free at 1-888-INFO-FDA (1-888-463-6332) or visit www.fda.gov. Consult your doctor for more information.

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National Diabetes Information Clearinghouse

1 Information Way
Bethesda, MD 20892–3560
Phone: 1–800–860–8747
TTY: 1–866–569–1162
Fax: 703–738–4929
Email: ndic@info.niddk.nih.gov
Internet: www.diabetes.niddk.nih.gov

The National Diabetes Information Clearinghouse (NDIC) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health of the U.S. Department of Health and Human Services. Established in 1978, the Clearinghouse provides information about diabetes to people with diabetes and to their families, health care professionals, and the public. The NDIC answers inquiries, develops and distributes publications, and works closely with professional and patient organizations and Government agencies to coordinate resources about diabetes.

Publications produced by the Clearinghouse are carefully reviewed by both NIDDK scientists and outside experts. This fact sheet was reviewed by William V. Tamborlane, M.D., Yale University.

This publication is not copyrighted. The Clearinghouse encourages users of this publication to duplicate and distribute as many copies as desired.


NIH Publication No. 09-4551
December 2008

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Page last updated October 4, 2013


The National Diabetes Information Clearinghouse is a service of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

National Diabetes Information Clearinghouse
1 Information Way
Bethesda, MD 20892–3560
Phone: 1–800–860–8747
TTY: 1–866–569–1162
Fax: 703–738–4929
Email: ndic@info.niddk.nih.gov
Internet: www.diabetes.niddk.nih.gov

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