The glucose sensor works by measuring the sugar in the interstitial fluid (the fluid that surrounds the cells, not the blood) through a very thin filament inserted under the skin. That filament takes readings continuously every few minutes and sends them wirelessly to a mobile phone or a reader, so you can see your glucose in real time and without sticking your finger. In this guide we explain in detail how the glucose sensor works, what types there are, their advantages compared to the traditional glucometer and who can use it.
How does the glucose sensor work?
A glucose sensor is a continuous monitoring device that measures your blood sugar levels in real time without the need for finger pricks. Its operation is based on four key elements:
A filament under the skin. The sensor incorporates a flexible and very thin filament that is inserted superficially under the skin, usually at the back of the arm, with the help of an applicator. It does not reach the blood: it stays in the layer where the interstitial fluid is.
Measurement in the interstitial fluid. Instead of analyzing blood, the sensor measures the glucose present in the interstitial fluid, the fluid that surrounds the cells. That's why you don't need to prick yourself: the reading is obtained continuously from that fluid.
Readings every few minutes. The sensor automatically takes and updates the glucose value every few minutes (some models, such as the FreeStyle Libre, update the reading up to every minute). This allows you to see not only the current value, but the trend: if your glucose rises, falls or remains stable.
Wireless transmission. The data is sent wirelessly to a receiving device, either a compatible smartphone or a specific reader. Many models display graphics and issue alerts when blood sugar is too high or too low, which helps make quick decisions.
An important detail: after placing the sensor, you must wait about 60 minutes for calibration before the first reading. During that hour the sensor is adapting to the body and does not provide data, which is completely normal.
Does the sensor measure blood glucose?
Not exactly. The sensor measures glucose in the interstitial fluid, not in the blood. Both values are very related, but the interstitial one is slightly out of phase with the capillary one. That's why, in moments of rapid change (after eating, after exercising or during a drop), the sensor value may differ a little from what a finger prick would give. It's a normal characteristic of the system, not a sensor failure.
Types of glucose sensors
Under the name of glucose sensor or diabetes patch, several continuous monitoring devices (CMD) coexist. The most well-known are the FreeStyle Libre from Abbott and the Dexcom. The FreeStyle Libre allows you to check your blood sugar by bringing your mobile phone or reader close to the sensor, and its FreeStyle Libre 2 model adds alerts for high and low levels. The Dexcom, on the other hand, sends the readings automatically and continuously to your mobile phone. All of them share the same operating principle: subcutaneous filament, measurement in interstitial fluid and wireless transmission.
How to place the glucose sensor
The placement is simple: clean and dry the area well (usually the back of the arm), prepare the applicator and apply the sensor with a firm movement so that the filament is inserted without pain. Then activate it with the reader or the app and wait for the calibration time. If you want the complete detail with all the steps and the exact recommended area, we explain it in our guide on Where to place the sensor step by step.
Advantages of the glucose sensor compared to the traditional glucometer
Compared to traditional blood glucose meters, a non-prick glucose sensor offers several advantages in everyday life:
- Less pain: It is not necessary to prick your fingers several times a day.
- Real-time readings: Allows continuous monitoring and see trends, not just a point value.
- Greater comfort: It can be used while performing daily activities.
- Better control: Helps detect patterns and prevent hypoglycemia and hyperglycemia before they occur.
Who can use a glucose sensor?
The glucose sensor is a comfortable option for several profiles: people with type 1 and type 2 diabetes who want to monitor their glucose continuously, patients who want to avoid frequent pricks, athletes with diabetes who need to control their levels at different times of the day, and children and adolescents who require more comfortable and less invasive control. In all cases, use should be guided according to the instructions of the medical team.
How long does a glucose sensor last?
The duration depends on the model. The FreeStyle Libre and the FreeStyle Libre 2 last up to 14 days, the FreeStyle Libre 3 Plus lasts up to 15 days and the Dexcom G6 is used for up to 10 days straight. For the sensor to complete its cycle without detaching prematurely due to sweat, water or friction, many users resort to protective patches.
Patches to protect the glucose sensor
Glucose sensor patches are adhesive accessories that fix and protect the device on the skin during its entire period of use. They are made of hypoallergenic and breathable materials, act as a barrier against blows and friction with clothes, and do not interfere with measurements. They are especially useful for active people or people with sensitive skin, because they prevent the sensor from falling off when swimming, sleeping or exercising.
Frequently asked questions about how the glucose sensor works
Does the glucose sensor measure in blood?
No. The sensor measures glucose in the interstitial fluid, the fluid that surrounds the cells, not in the blood. That's why there may be a slight lag with the value of a finger prick when glucose changes quickly.
How often does the sensor measure glucose?
The sensor takes readings continuously and updates the value every few minutes. Some models, such as the FreeStyle Libre, update the reading up to every minute and store several hours of data.
Does it hurt to wear a glucose sensor?
The placement is practically painless because the filament is very thin and is inserted superficially. Once installed, most users do not notice it during daily use.
How long does the sensor last?
Between 10 and 15 days depending on the model: the FreeStyle Libre lasts up to 14 days, the 3 Plus up to 15 and the Dexcom G6 up to 10. Then you have to replace it with a new one.
Take care of your glucose sensor with Glucody products
Now that you know how the glucose sensor works, you know that keeping it well fixed is key for the readings to be reliable during all days of use. At Glucody you will find a wide selection of Patches to protect the glucose sensor, adapted to the different models, with resistant, breathable and safe materials for the skin.
