Continuous Glucose Monitoring (CGM): How It Can Prevent Low Blood Sugar Emergencies

Joseph R. Anticaglia, MD
Medical Advisory Board

Vanessa is an 11 year old with type 1 diabetes who presented to the emergency department for the third time within the past 12 months because of “problems with her sugar.” She was unconscious, in hypoglycemic shock (extremely low blood glucose level) and clinging to life.

The doctors weren’t able to start an intravenous in the customary fashion by placing a needle in the vein. Time was of the essence and a “cutdown” was performed. This procedure involves making an incision in the skin to expose the vein and then insert a large needle in the vein to administer lifesaving fluids and minerals.

Type 1 Diabetes is a chronic condition in which the pancreas produces little or no insulin. It characteristically appears in adolescence. The body needs the hormone insulin to break down sugars (metabolizes them) so they can be used as a source of energy. These patients require insulin injections or insulin pump therapy to treat this condition.

Type 2 Diabetes used to be called adult onset diabetes but today more children are obese and being diagnosed with this condition. These patients don’t produce enough insulin or their bodies don’t metabolize it properly. If diet, exercise or losing weight doesn’t control type 2 diabetes, insulin therapy is used to manage the disease. How does CGM impact people with diabetes?

Continuous Glucose Monitoring

CGM uses a device to measure a person’s glucose levels on a continuous basis, 24 hours a day. Between the cells of our body is fluid called interstitial fluid. The CGM measures the changing glucose levels in this fluid automatically. The device consists of three parts:

Getty Stock photo Diabetic teen showing CGM sensor and monitor

The sensor, the size or a penny or a quarter, is usually placed on the skin of the arm or abdomen. It has electrodes that go just below the skin which picks up the glucose levels from the fluid between cells. The sensor sends the information to the transmitter.

The transmitter accepts the information and relays it wirelessly to a monitor or to an apple or android smart phone. It shows the glucose level numbers every few minutes. Individuals with this disease receive alarm signals alerting them to glucose levels that are trending dangerously high or low.

Indications of CGM

If you’re a patient or have a loved one with type 1 or type 2 diabetes using an insulin pump or needing insulin injections, you might be a candidate for CGM. Also, if you frequently test your blood sugar levels and need to adjust your insulin dosage, it’s worthwhile to investigate the usefulness of CGM.

Benefits of CGM

Drawbacks of the CGM System

It takes time for glucose to travel from the bloodstream into the interstitial fluid. The lag time varies from five to 20 minutes and depends on the person and the device you use to monitor the glucose level. Newer versions of CGM have reduced the lag time. It also takes time to familiarize yourself with the CGM devise


In many respects diabetes is a numbers game. People know the range of their blood glucose levels and how to use insulin in the recommended dosage. CGM gives you time to take corrective action if the glucose levels are too high or too low.

By maintaining your glucose numbers within a normal range, you help prevent long term complications such as:

Continuous glucose monitoring does not replace blood glucose readings (finger-prick blood tests). But it does tell a story about how your glucose levels are trending in the morning, afternoon and at night. And the glucose alerts relayed to Vanessa mom’s smart phone saved the youngster and her mother several terrifying experiences in the emergency department.


  1. Robert Tannenberg, MD et al; Use of the Continuous Glucose Monitoring System to Guide Therapy in Patients with Insulin-Treated Diabetes: A Randomized Controlled Trial; Mayo Clinic Proceedings, December, 2004
  2. Steven J. Russell, MD, PhD; Continuous Glucose Monitoring; National Institute of Diabetes and Digestive and Kidney Diseases, (NIDDK)
  3. Cleveland Clinic; Continuous Glucose Monitoring

This article is intended solely as a learning experience. Please consult your physician for diagnostic and treatment options.