The FreeStyle Libre system allows people with diabetes to check their glucose without a skin prick, but there are concerns about its lack of alarms.

Type 1 and type 2 diabetes technology and medications have come a long way since the invention of insulin in 1921.

But day-to-day management still requires countless finger pricks to draw blood and measure glucose levels.

FreeStyle Libre Flash Glucose Monitoring System, manufactured by Abbott Diabetes Care Inc. and officially approved on September 27 by the U.S. Food and Drug Administration (FDA), strives to be a true game-changer for people with diabetes.

Unlike the Dexcom or Medtronic’s Guardian and Enlite continuous glucose monitors (CGM), which require a minimum of twice-daily finger pricks to calibrate the CGM’s readings with that of a traditional blood glucometer, the Libre system requires zero calibration.

The technology is still similar in that the Libre also uses a small sensor wire that a patient inserts into their subcutaneous tissue.

This sensor measures glucose levels in the interstitial (body fat) fluid versus glucose in the bloodstream.

Where the technology continues to differ greatly is in how the glucose levels measured by the sensor wire are then reported to the person using it.

From the get-go, the Libre requires a lengthy 12-hour startup period before the sensor is able to measure and report glucose levels while the Dexcom and Medtronic sensors startup window is a mere two hours.

The most significant difference between these technologies is that the Libre isn’t “continuous.”

When a patient wants to measure their blood glucose level, the Libre requires them to wave a small handheld “mobile reader” over the part of the body where their sensor is located.

The handheld device then displays the glucose level, allowing the user to determine if it’s too high (hyperglycemia) or too low (hypoglycemia).

Dexcom and Medtronic CGMs both send blood glucose data wirelessly to a handheld device (or the user’s own iPhone), which displays a simple graph with new glucose measurements automatically marked every five minutes.

The Libre sensor itself can be used for up to 10 days.

Dexcom and Medtronic’s sensors are FDA approved for use up to seven days, but users of these CGMs have learned that simply stopping and restarting the sensor’s “startup” process enables them to use a sensor for as long as the sensor’s tape keeps it attached to their body.

Many report getting 10 to 14 days out of a sensor.

“I’ve gotten as much as 22 days out of one Dexcom sensor,” reports Sarah “Sugabetic” Kaye, who has lived with type 1 diabetes for 29 years and is well-known in the blogging community for her diabetes technology reviews at

All three glucose monitoring technologies provide a graph on their handheld devices, allowing patients and their healthcare providers to identify patterns and make changes in their medication regimen and improve overall blood glucose levels.

As groundbreaking as the FreeStyle Libre’s prick-less and zero-calibration system may be, the most notable shortcoming of this new technology is its lack of alarms.

“Libre is a good option for those who don’t check their blood sugar a whole lot using traditional finger-stick meters,” explained Gary Scheiner, MS, CDE, author of “Think Like a Pancreas” and founder of Integrated Diabetes Services.

“It’s easy to use and minimally inconvenient. And it will provide healthcare providers with some robust data for making beneficial recommendations and adjustments,” he told Healthline.

“However, I don’t think many current CGM users will (or should) switch to Libre since it lacks those all-important high and low blood sugar alerts. Without early high and low warnings, users open themselves up to potentially dangerous hypoglycemia as well as prolonged and more severe hyperglycemia.”

In addition to simply alerting patients when their blood glucose levels are rising or falling with indicating arrows, Dexcom and Medtronic technology allow them to customize their own alarm settings, and automatically alert them if glucose levels drop below 55 milligrams per deciliter (mg/dL).

This customizable alert feature is crucial, for example, because the blood sugar goals for a patient during pregnancy will be tighter than the goals of a non-pregnant patient.

Blood sugar goals for a teenager or a young child are generally going to be far more lenient than they would be for an adult.

Those with a history of “hypoglycemia unawareness,” in which they no longer experience symptoms of low blood sugars such as lightheadedness and trembling, would likely want to be alerted far sooner than others.

For parents of children with diabetes, the alarms provide a level of security and peace of mind, especially while children are sleeping, playing sports, at recess, or at a friend’s home for a sleepover.

The lack of alarms in the Libre isn’t just an inconvenience, it may actually deem the technology useless for many.

This crucial detail is likely the strongest motivators for a patient being willing to wear a sensor wire in their flesh 24 hours a day, 7 days a week.

“For me, the purpose of a monitoring system is to have those alerts and alarms,” Kaye told Healthline. “If it doesn’t do that, then using a standard meter is just as good as the Libre in my opinion. To be honest, the Libre is not even on my radar of interest because of the lack of alarms.”

While all of the sensors themselves are thin and short, they are inserted with a large, thick needle, which is a quick but still painful application process.

Possible side effects of wearing any type of sensor include skin rashes due to the medical tape, constantly healing punctures from past sensor locations, and the constant presence of the noticeable external parts of the device that can be as thick as a stack of three or four quarters sitting on the skin.

The trade-off for that sometimes tedious discomfort is the safety and security provided by the alarms.

Those pertinent alarms are also perhaps the only way to reduce the anxiety and worry that any patient (or their parents) taking daily doses of insulin inevitably experience due to the risks associated with taking even just slightly too much or too little.

“The Libre feels like a good replacement for your traditional blood glucose meter,” explained Scott Benner, host of the all-things-diabetes Juicebox Podcast and whose daughter was diagnosed with type 1 diabetes as a toddler. “However, the lack of the ‘C’ in the ‘CGM’ makes the Libre an unworthy competitor to the Dexcom [or Medtronic] device. The ‘C’ in continuousglucose monitoring is where the value lies.”

Already available in more than 40 countries, the FreeStyle Libre system is expected to be available in the United States by the end of this year.

Editor’s note: Ginger Vieira is an expert patient living with type 1 diabetes, celiac disease, and fibromyalgia. Find her diabetes books on and connect with her on Twitter and YouTube.