Updated: May 2026 · by Sonja Spörlein, founder of Zuckerschmuck and Type 1 for 30 years
🩹 At a Glance: Libre 1, 2 and 3 Compared
In short: All three sensor generations measure tissue sugar (interstitial fluid), not directly in the blood — which explains a certain natural delay compared to blood glucose values.
- FreeStyle Libre 1: 14 days wear time · no real-time alarms · MARD approx. 11.4% according to Pivotal study [2]
- FreeStyle Libre 2: 14 days wear time · optional hypo/hyper alarms · improved algorithm [3]
- FreeStyle Libre 3: 14 days wear time · real-time streaming to smartphone · significantly smaller sensor · still no calibration option [1]
- Manufacturer of all three: Abbott Diabetes Care
MARD (Mean Absolute Relative Difference) = mean absolute percentage deviation of the sensor from a laboratory reference value. The lower, the more accurate. A MARD of 10% is considered clinically good.
💜 Why I've been wearing the Libre since 2015
I have been using the FreeStyle Libre 1 since its market launch in Germany in November 2015 — and it was the impetus for me to found Zuckerschmuck. Only during my pregnancy did I switch to the Dexcom G5 due to the lack of an alarm function. However, since I always felt the Dexcom G5 on my body and found it quite clunky, I returned to the Libre afterwards — it has better wearing comfort, I simply like it. I just missed the alarm function at night compared to the Dexcom.
🧪 What I was interested in with the Libre 2
In short: I was particularly interested in whether the Libre 2 really measures "better" than the Libre 1.
That's why I was thrilled that Abbott equipped the FreeStyle Libre 2 with alarm functions and that I was allowed 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
Therefore, I wore Libre 1 and 2 in parallel and measured my blood glucose values at the same time. Here are my results — pink = FreeStyle Libre 1, blue = FreeStyle Libre 2, with blood glucose measurement from the finger in between:
✅ Good Agreements
In short: In most comparative measurements, Libre 1, Libre 2, and blood glucose values were closely aligned.
The first three images show good agreement between Libre 1, Libre 2, and blood glucose measurement. Unfortunately, there were also other results:
⚠️ Poor Agreement — this is also a reality
In short: For individual sensors, a constant deviation was observed — mostly in one direction and throughout the entire wear time.
Of course, I measured more comparative values than those shown here — this is just an exemplary excerpt, but the results are representative.
📣 My Conclusion
Briefly in advance: This is my personal experience as a Type 1 diabetic for 30 years — not treatment advice. Please always discuss therapy decisions with your diabetology practice.
For me personally, there have always been sensors that were closer to the measured blood glucose values, and sensors that had a (regular!) deviation. In the first 24 hours, the sensors usually also measure less accurately than in the subsequent runtime. I have always made at least one comparative blood measurement with basal values (stable values without previous carbohydrate or insulin administration) per day to the Libre sensor to get feedback on whether I can rely quite accurately on the Libre or if I have to account for a certain difference in my head.
Because I have found that sensors with a deviation from the blood glucose value almost always deviate in the same direction, either up or down — and the deviation remains very similar regardless of the level of glucose/blood glucose values (e.g., always +approx. 30 mg/dl to the actual value or approx. -20 mg/dl to the actual value). Therefore, even with a deviating sensor, I was able to make good therapy decisions for myself and always felt very safe with the Libre. My HbA1c values were also in good 6er-HbA1c ranges with Libre and very few comparative blood glucose measurements.
Where it gets critical: with alarms
Deviations become critical when you rely on alarm signals. And annoying when you are woken up unnecessarily at night due to an alleged hypo. This happened to me once: Libre gave an alarm for <60 mg/dl, my measured blood glucose value was an uncritical 92 mg/dl and was not falling either. That makes you irritated and a little insecure, and you don't fully trust the Libre values and alarms anymore. Maybe this is because I belong to the small percentage of Libre users whose sensors, according to my diabetologist, have inexplicable deviations. There would be nothing to be done then.
💭 My Wish — and the Update on FreeStyle Libre 3
But I would have a solution, because I find the Libre so great in terms of handling and size that no other CGM can keep up: I wish there would soon be a "FreeStyle Libre 3" with the option for calibration. Then I could "calibrate away" my deviations and trust the measurement results and alarms more. 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 most important difference: The Libre 2 has optional real-time alarms for high and low glucose levels, the Libre 1 does not. The algorithm has been slightly revised, both last for 14 days. Sensor shape 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, streams values automatically to your smartphone every minute (instead of requiring scanning) and comes with hypo/hyper alarms as standard. Both sensors are factory calibrated, both last 14 days, and both come without a calibration option [1].
How accurate is the FreeStyle Libre 2 really?
Clinical studies show a MARD value (mean absolute percentage deviation) in the range of approx. 9–11.4% for the Libre sensor family — for Libre 1 it was 11.4% in the Pivotal study [2], newer algorithm versions achieve approximately 9.2% depending on the study [3]. Important: these are average values; individual sensors can 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. In case of persistent deviation, the only option is to mentally account for the difference or to consult your diabetology practice.
What does a MARD value mean?
MARD stands for "Mean Absolute Relative Difference" — meaning the average absolute percentage deviation of the sensor from a laboratory reference blood glucose value. The lower the value, the more accurate. A MARD below 10% is considered clinically good [2,3]. Important to know: MARD is an average — individual measurements can deviate significantly.
What to do if the Libre gives false hypo alarms?
First step: cross-check with a fingerstick. If the deviation is significant and persists for several days, consider a sensor complaint to Abbott (product complaint via the FreeStyle hotline). For recurring alarms, speak with your diabetology practice — another CGM system may be more suitable for you [4].
🛍️ Tapes, Stickers and Sensor Holders for your Libre
Do you use a FreeStyle Libre and want to wear the sensor discreetly or make it more colorful? At Zuckerschmuck you will find:
- Sensor stickers for FreeStyle Libre 1, 2 and 3
- Sensor holder headband system and interchangeable strap holders
- Cover-up tapes
- Cases for the Libre reader
📚 Methodology Note & Sources
Methodology: The comparative measurements shown in the article were carried out privately in everyday life — Libre 1 and Libre 2 in parallel on the body, blood glucose measurement from the finger as a reference. The images show an exemplary excerpt. This is a private N=1 self-observation — not a clinical study. Statistically reliable accuracy values come from the manufacturer 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 [Accessed: 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/ [Accessed: 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/32842770/ [Accessed: 08.05.2026].
- Deutsche Diabetes Gesellschaft (DDG), Bundesärztekammer, AWMF. S3-Leitlinie Therapie des Typ-1-Diabetes. AWMF-Register-Nr. 057-013. 2. Auflage; 2023. Available at: https://www.awmf.org/leitlinien/detail/ll/057-013 [Accessed: 08.05.2026].
- Heinemann L, Kamann S. Adhesives Used for Diabetes Medical Devices: A Neglected Risk With Serious Consequences? J Diabetes Sci Technol. 2016;10(6):1211–1215. Available at: https://pubmed.ncbi.nlm.nih.gov/27562857/ [Accessed: 08.05.2026].
Note: This article is a personal experience report and does not replace medical or diabetological advice. The choice of a CGM system and the evaluation of sensor values should be made in consultation with your diabetology practice.
Yours, Sonja
Founder of Zuckerschmuck and Type 1 for 30 years
