The Freestyle Libre Continuous Glucose Monitor

continous glucose monitor
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The Freestyle Libre System is a continuous glucose monitor (CGM) worn on the upper arm that provides real-time blood glucose (blood sugar) readings every minute for people over 18 who have type 1 diabetes and for those who take insulin. It has been reported that people who frequently test their blood sugar have lower A1Cs (a measure of average glucose levels over two to three months) and steadier glucose levels.

However, traditional monitoring can be intensive and invasive and requires multiple fingersticks to draw and test blood each day. Continuous glucose monitors like the Freestyle Libre can greatly simplify this process.

How It Works

The Freestyle Libre System uses modern technology to provide real-time glucose readings every minute using a pre-calibrated sensor. Unlike other CGMs, there is no bulky transmitter; instead, a small, water-resistant sensor (roughly the size of two stacked quarters) is inserted 5 millimeters under the skin on the back of the arm where it measures interstitial fluid, which is comparable to capillary blood.

Timing and Duration

After a one-hour startup period, you can retrieve a blood glucose reading instantly by scanning the sensor with your smartphone app or reader. You can scan as often as you'd like, but in order to capture all data, it is recommended that you scan your sensor at least once every eight hours to record 100% of the data.

Studies conducted by Abbott, the maker of the Freestyle Libre, have demonstrated that people who use this sensor wind up scanning the sensor more often than they would test their blood sugar with a fingerstick, which provides them with more accurate data.

The Libre can store 90 days' worth of data and can be worn for up to 14 days, at which point it stops working and must be replaced. Once you are finished with your sensor, you can dispose of it.

When Manual Testing May Be Necessary

The Libre also has a blood glucose meter within the system. This can allow you to doublecheck that the CGM is accurate. Inaccuracies sometimes occur with CGMs during rapid changes in blood glucose, such as after eating, dosing insulin, or exercising. Severe dehydration and excessive water loss may also cause inaccurate results. During these times, you'll need to confirm your blood sugar level with a fingerstick.

The Freestyle Libre also will alert you if for some reason it isn't able to determine where your glucose is trending by displaying a warning symbol. Whenever you see this symbol, you should do a finger prick blood glucose test.

The Freestyle Libre is not designed to let the wearer know if their glucose levels are too high or too low. If you begin having symptoms of either condition, check your blood sugar manually.

Cost

For people who have private insurance or are on Medicaid, the Freestyle Libre may cost $40 to $75 per month. The device is fully covered by Medicare for those who qualify; in fact, it is one only a few CGMs covered by Medicare. It is available in pharmacies nationnwide; your doctor can help you locate one. Download the buying guide from the Freestyle Libre website to find a list of providers.

In addition to the cost of the device, the Freestyle Libre uses test strips called Precision Neo test strips. Typically, a box of 50 costs about $20. They are individually foil-wrapped so that they can be used until the expiration date. Using other test strips with the built-in meter may produce an error or cause it to not turn on or start a test. You cannot use the meter to test for ketones.

Benefits

Freestyle Libre is the first CGM that eliminates fingersticks for calibration. Instead of checking fingersticks multiple times per day, people with diabetes can scan their CGM (a painless procedure) to get real-time glucose readings that they can use for insulin dosing, meal planning, etc.

For those people who loathe testing, this could help them to better manage their diabetes, In addition, large amounts of data and trend reports can help people with diabetes reduce their risk for low blood sugar and help them to figure out insulin dosing and meal planning..

Comparison to Other Devices

The Libre device is referred to as a flash glucose monitoring system. As compared to other CGMs, like the Dexcom G4 and G5, the Libre system checks glucose every minute rather than every five minutes and it can be worn for 14 days as opposed to seven. It is very accurate and does not require fingerstick calibrations. Because the Libre does not require a transmitter, the price for it and its sensors is lower compared to other CGMs.

Additionally, sensor placement is not approved for sites other than the back of the arm (other CGMs are approved for belly and buttocks placement). If placed in other areas, the sensor may not function properly.

Caveats

The Freestyle Libre does not feature automatic alarms to alert the wearer of too-high or too-low blood glucose levels. However, if after scanning your levels are abnormal, the reader will alert you and prompt you to set a reminder to scan again. Be aware the Freestyle Libre has not been evaluated for use by people with hypoglycemia unawareness (meaning they are unable to recognize the symptoms of a extreme dip in blood sugar levels).

Storage

Storage is important for protecting the sensor and keeping the readings as accurate as possible. The Freestyle Libre kit should be stored at a temperature between 39 degrees Fahrenheit (3.8 degrees Celsius) and 77 degrees Fahrenheit (25 degrees Celsius) and at non-condensing humidity of between 10% and 90%. It your refrigerator meets these criteria you can certainly store the kit there.

The Libre has not been evaluated for use in people with hypoglycemia unawareness, nor for anyone less than 18 years of age.

A Word From Verywell

The Freestyle Libre Glucose Monitoring System is the first CGM to eliminate fingerstick calibration. This is exciting news for people with diabetes.

One major difference to consider before discussing this with your physician is that the Libre System does not have built-in alarms and is not meant for patients younger than 18 years of age. Eligible patients with diabetes must receive a prescription to get this meter. If you think you are eligible and are interested, ask your healthcare team about it. If you have any doubts, you can always see if you can trial the Freestyle Libre before getting started.

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Article Sources
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  2. Blum A. Freestyle Libre Glucose Monitoring System. Clin Diabetes. 2018;36(2):203-204. doi:10.2337/cd17-0130

  3. Abbott Laboratories. FreeStyle Libre 14 Day System.

  4. Abbott. FreeStyle Libre 14 Day Indications and Important Safety Information. Verified September 2018.

  5. Abbott. FreeStyle Libre - Medicare Guide. Last Updated March 29, 2018.

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