Updated: May 2026 · by Sonja Spörlein, founder of Zuckerschmuck and living with type 1 since the age of 7
🩹 At a glance: Libre 1, 2 and 3 compared
All three glucose sensor generations measure glucose in the interstitial fluid, not directly in the blood like a traditional blood glucose meter used for fingersticks. This explains a certain natural delay compared with blood glucose readings, averaging 2.4 minutes in adults in the accuracy study of Libre 2 [3].
- FreeStyle Libre 1: 14 days of wear · no real-time alarms · MARD of approx. 11.4% according to the pivotal study [2]
- FreeStyle Libre 2 (also often written as Free Style Libre 2 or Libre2): 14 days of wear · optional low/high glucose alarms · improved algorithm [3]
- FreeStyle Libre 3: 14 days of wear · real-time streaming to a smartphone · significantly smaller sensor · still no calibration option [1]
- FreeStyle Libre 3 Plus: up to 15 days of wear · since 15 October 2024, the only Libre sensor for self-paying and privately insured customers [5]
- Manufacturer of all four: Abbott Diabetes Care
MARD (Mean Absolute Relative Difference) = the sensor’s mean absolute percentage deviation from a laboratory reference value. The lower it is, the more accurate it is. A MARD below 10% is considered clinically good.
💜 Why I’ve been wearing Libre since 2015
I have been using the FreeStyle Libre 1 since its market launch in Germany in November 2015, and it was the reason I founded Zuckerschmuck. I only switched to the Dexcom G5 during my pregnancy because it lacked an alarm function. However, since I could always feel the Dexcom G5 on my body and found it rather bulky, I switched back to the Libre afterward. It is more comfortable to wear, and I simply like it. I only somewhat missed the alarm function at night compared with the Dexcom.
🧪 What interested me about the Libre 2
That is why I was absolutely delighted that Abbott equipped the FreeStyle Libre 2 with alarm functions and allowed me to test it. What interested me most was whether it was true that the Libre 2 measures “better” than the Libre 1.
📊 My setup: Libre 1 + Libre 2 + blood glucose in parallel
That is why I wore Libre 1 and 2 in parallel while also measuring my blood glucose levels at the same time. Here are my results compared with the blood glucose measurement from my finger:
✅ Good matches
In most comparison measurements, Libre 1, Libre 2, and blood glucose levels were very close to one another.
Unfortunately, there were other results too:
⚠️ Poor matches: this is also reality
Some sensors showed a constant deviation, usually in one direction and throughout the entire wear period.
Of course, I took more comparison readings than the ones shown here. This is just an illustrative excerpt that reflects my impression from the other measurements.
📣 My conclusion
A brief note beforehand: This is my personal experience as a person with type 1 diabetes since the age of 7, not treatment advice. Please always discuss treatment decisions with your diabetes care team.
Personally, there have always been sensors that were closer to the measured blood glucose levels, as well as sensors that showed a (regular!) deviation. During the first 24 hours, sensors also tend to measure less accurately than during the rest of their wear time. I have always taken at least one comparison blood glucose measurement per day against the Libre sensor, using baseline readings, i.e. stable levels without any preceding carbohydrate or insulin doses. This gives me feedback on whether I can rely on the Libre fairly precisely or whether I need to factor in a certain difference mentally.
Because I have found that sensors with deviations from the blood glucose level almost always deviate in the same direction, either upward or downward, and that the deviation remains very similar regardless of the level of the glucose/blood glucose readings (for example, always approximately +30 mg/dl from the actual value or approximately −20 mg/dl from the actual value). That is why I was still able to make good treatment decisions for myself even with a deviating sensor, and I always felt very safe with the Libre. My HbA1c levels were also in the good 6-range with the Libre and only very few comparative blood glucose measurements.
Where it gets critical: with alarms
Deviations become critical when you rely on alarm signals. And it is frustrating when you are woken up at night for no reason because of an alleged hypo. This happened to me once: Libre gave an alarm for <60 mg/dl, while my measured blood glucose level was an unconcerning 92 mg/dl and was not falling either. That leaves you irritated and somewhat unsettled, and you no longer fully trust the Libre readings and alarms. Maybe this is because I apparently belong to the small proportion of Libre users whose sensors have unexplained deviations, according to my diabetologist. In that case, there would be nothing to do.
💭 My wish and the update on the FreeStyle Libre 3
But I do have a solution, because I like the Libre's handling and size so much that no other CGM can compete: I wish there would soon be a “FreeStyle Libre 3" with a calibration option. Then I could “calibrate away" my deviations and have more confidence in the readings and alarms. Because I am and will remain a Libre fan 🌈
❓ Frequently asked questions about FreeStyle Libre 1, 2 and 3
What is the difference between FreeStyle Libre 1 and 2?
The key difference: Libre 2 has optional real-time alarms for high and low glucose levels, while Libre 1 does not. The algorithm was slightly revised, and both last 14 days. The sensor design and applicator are largely identical [1].
What is the difference between FreeStyle Libre 2 and 3?
The Libre 3 is significantly smaller and flatter than the Libre 2, automatically streams readings to your smartphone every minute (instead of requiring scanning), and comes with low/high glucose alarms as standard. Both sensors are factory-calibrated, both last 14 days, and neither offers a calibration option [1].
How accurately does the FreeStyle Libre 2 really measure?
Clinical studies show a MARD value (mean absolute percentage deviation) of approximately 9 to 11.4% for the Libre sensor family. For Libre 1, it was 11.4% in the pivotal study [2]; for Libre 2, with a revised algorithm, it was 9.2% for adults and 9.7% in the kids group in the accuracy study [3]. Important: These are average values, and individual sensors may deviate more significantly.
Can I calibrate the FreeStyle Libre?
No. All three sensor generations (Libre 1, 2, 3) are factory-calibrated; you cannot calibrate them yourself to a blood glucose value. If the deviation is persistent, the only options are to mentally factor in the difference or speak with your diabetes care team.
What does a MARD value mean?
MARD stands for “Mean Absolute Relative Difference”, meaning the sensor’s mean absolute percentage deviation from a laboratory reference blood glucose value. The lower the value, the more accurate it is. A MARD below 10% is considered clinically good [2,3]. Important to know: MARD is an average, and individual readings may deviate significantly.
What to do if the Libre gives false low glucose alarms?
My first step is to check with a finger prick. If the difference is significant and persists for several days, check with Abbott about making a sensor complaint (product complaint via the FreeStyle hotline). If alarms recur, talk to your diabetes practice; another CGM system may be more suitable for you [4].
Why do the sensor and blood glucose meter show different readings?
The sensor measures glucose in the tissue, while the blood glucose meter measures glucose in the blood when you prick your finger. Tissue glucose follows blood glucose with a slight delay, averaging 2.4 minutes in adults in the Libre 2 study [3]. In addition, each individual sensor has its own deviation, which MARD describes only as an average. According to Abbott, an additional check with a blood glucose meter is required if your symptoms do not match the readings or alarms [7].
How accurate is the FreeStyle Libre compared with the Dexcom G7?
The figures come from different studies and are therefore only roughly comparable. For the FreeStyle Libre 2, the MARD was 9.2% for adults in the accuracy study [3], while the Dexcom G7 had 8.2% with the sensor on the upper arm and 9.1% on the abdomen in its accuracy study [6]. Both are therefore in the single-digit range. In everyday use, the systems differ more in wear time (Libre 2: 14 days, Dexcom G7 in the study: 10.5 days), size and operation. You can find more about the G7 in our Dexcom G7 experience report.
Can I try the FreeStyle Libre for free?
Abbott offers a testing program: people with diabetes fill out a questionnaire and can then order a test sensor free of charge. The program page advertises 15 days of glucose readings on a smartphone [7].
🛍️ Tapes, stickers and sensor holders for your Libre
Do you use a FreeStyle Libre and want to wear the sensor discreetly or add some color? At Zuckerschmuck, you'll find:
- Sensor stickers for FreeStyle Libre 1, 2 and 3
- sensor holder strap system and changeable strap holder
- Overlay tapes for covering
- TapeCover for Freestyle Libre 1 and 2
- Pouches for the Libre reader
📚 Methodology note & sources
Methodology: The comparison measurements shown in the article were conducted privately in everyday life: Libre 1 and Libre 2 worn simultaneously, with blood glucose measured from a fingerstick as the reference. This was a private self-observation involving a single person (N=1), not a clinical study. Statistically reliable accuracy values come from the manufacturers' and pivotal studies (see sources).
- Abbott Diabetes Care. FreeStyle Libre 2 / FreeStyle Libre 3, Instructions for Use. Wiesbaden: Abbott Laboratories. Available at: https://www.freestyle.abbott/de-de [Zugriff: 08.05.2026].
- Bailey T, Bode BW, Christiansen MP, Klaff LJ, Alva S. The Performance and Usability of a Factory-Calibrated Flash Glucose Monitoring System. Diabetes Technol Ther. 2015;17(11):787–794. Available at: https://pubmed.ncbi.nlm.nih.gov/26171659/ [Zugriff: 08.05.2026].
- Alva S, Bailey T, Brazg R, Budiman ES, Castorino K, Christiansen MP, et al. Accuracy of a 14-Day Factory-Calibrated Continuous Glucose Monitoring System With Advanced Algorithm in Pediatric and Adult Population With Diabetes. J Diabetes Sci Technol. 2022;16(1):70–77. Available at: https://pubmed.ncbi.nlm.nih.gov/32954812/ [Zugriff: 14.09.2026].
- German Diabetes Association (DDG). S3 guideline on the treatment of type 1 diabetes. AWMF registry no. 057-013. Version 5.1, dated 02.09.2023. Available at: https://www.awmf.org/leitlinien/detail/ll/057-013 [Zugriff: 08.05.2026].
- Abbott Diabetes Care. FreeStyle Libre 3 Sensor (note on the FreeStyle Libre 3 Plus for self-pay patients since 15.10.2024). Available at: freestylelibre.de [Zugriff: 14.09.2026].
- Garg SK, Kipnes M, Castorino K, Bailey TS, Akturk HK, Welsh JB, et al. Accuracy and Safety of Dexcom G7 Continuous Glucose Monitoring in Adults with Diabetes. Diabetes Technol Ther. 2022;24(6):373-380. Available at: https://pubmed.ncbi.nlm.nih.gov/35157505/ [Zugriff: 14.09.2026].
- Abbott Diabetes Care. FreeStyle Libre test program. Available at: fsl3.freestyle.abbott [Zugriff: 14.09.2026].
Note: This article is a personal account of experience and is not a substitute for medical or diabetes care advice. The choice of a CGM system and the evaluation of sensor readings should be handled by your diabetes care team.
Yours, Sonja
Founder of Zuckerschmuck and living with type 1 since the age of 7
Related topic
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- TapeGuard for difficult insertion sites: The masking aid for sites where standard tapes fail.
- Abbott Freestyle Libre 2 and 3 at a Glance: Features, differences, and the Libre 3 Plus.
