Privacy-Friendly Usage Analytics for a Class I Medical Device
How the femCycle period tracking app integrates app analytics despite strict privacy requirements
How the femCycle period tracking app integrates app analytics despite strict privacy requirements
femCycle is an app for people experiencing menstrual symptoms and has been placed on the market as a Class I medical device under the EU Medical Device Regulation (MDR). Users track their symptoms in a structured way and receive evidence-based recommendations from holistic medicine to help them alleviate their symptoms on their own. Analyzing menstrual cycle data also helps users better prepare for consultations with doctors. The app can be used even without a confirmed diagnosis and is not a substitute for medical advice.
Behind the app are the two founders, Carina Seliger and Mahja Sarschar, who are developing femCycle from Lübeck. They are supported by a network of independent experts in design, regulatory affairs, and other fields. femCycle has received funding from the EXIST startup grant and the Schleswig-Holstein startup grant.
A new version of the femCycle app will be released in November 2026. For the first time, it will include recipe ideas tailored to each phase of the cycle, complementing the existing cycle tracking and daily recommendations.
The team places great importance on providing users with transparent information about data processing. femCycle does not sell data and does not share health data for advertising purposes. This is a deliberate decision: Period-tracking apps are repeatedly criticized for sharing data with advertising networks - for example, to display personalized, cycle-based ads (such as for pain relievers, period underwear, or baby clothes). Data protection advocates have serious concerns about this type of secondary use of data.
femCycle
Die digitale Unterstützung bei Zyklusbeschwerden
Wer sich bis zum 31. Oktober 2026 in der App registriert, erhält als Gründungsmitglied dauerhaft 10% auf das Jahresabo.
femCycle’s core target audience consists of menstruating women aged 18 to 39 who experience recurring menstrual symptoms such as pain, mood swings, PMS, or hormonal imbalances. Often, the underlying cause of these symptoms remains unclear for a long time: For gynecological conditions such as endometriosis, it takes an average of about seven and a half years from the first symptoms to diagnosis; for pain-related symptoms, it can take up to ten years. femCycleaims to make this time easier for those affected: with recommendations that help them alleviate symptoms on their own, and with an analysis of cycle data that better prepares them for discussions with health professionals.
In May 2026, the femCycle app was launched on Menstrual Hygiene Day. Following media coverage of the launch, several hundred users signed up in a very short time - there are now over 1,000 users. This is a clear indication of the significant need for a privacy-friendly cycle-tracking app that also provides support in managing cycle-related symptoms.
Data Protection and App Tracking for Medical Devices
femCycle is a Class I medical device, meaning that, in addition to the GDPR, the EU Medical Device Regulation (MDR) also applies. The MDR governs topics such as risk and quality management. It also sets specific requirements for safety and performance. There are also specific European guidelines for medical device software, including those on qualification, classification, and cybersecurity.
For the femCycle team, it was therefore important to collect as little data as necessary from users. However, completely foregoing usage analytics isn’t practical, as the data is needed to improve the user experience and make informed product and roadmap decisions.
That’s why the recommendation for TelemetryDeck from Mira Jago - owner of an app agency and an expert in digital health applications and ethics in software development - came at just the right moment. The analytics service is based on a “privacy-by-design” approach: user IDs are hashed on the device and anonymized a second time on the server; IP addresses are not stored. Only events defined by the app team itself are recorded - in the case of femCycle, these are designed so that they do not allow any inferences to be drawn about health data.
As a manufacturer of a medical device, we need to understand how our app is used in everyday life - at the same time, users entrust us with very personal data. Therefore, data protection isn’t a compliance task at the end of the process, but an architectural decision at the very beginning: We collect only what we truly need for further development. We want to know which features are helpful - not who is using them.
Mahja Sarschar, Co-Founder & CTO of femCycle
Usage analytics provide the foundation for data-driven decisions
Setting up TelemetryDeck was “super easy,” explains Mahja: The basic integration was completed in just a few minutes. The TelemetryDeck support team provided quick and straightforward assistance in customizing the JavaScript SDK for React Native and Expo. Since then, the app has been capturing exactly the events the team needs to analyze usage behavior. The dashboards were set up well in advance of the launch - and in the days following the launch, it was a special moment for the team to watch them gradually fill up in real time.
After just a few weeks, it has become routine to review the usage metrics together in TelemetryDeck’s web dashboard during the weekly team meeting. This allows the team to make data-driven decisions for the app’s further development and optimization.
The data has shown us that our users are particularly interested in the nutrition section. That’s why we’ve expanded it over the past few months in collaboration with experts in nutritional science - the new recipe ideas are a direct result of this. This is exactly why we need usage analytics: to see what works, without knowing who’s using it.
Mahja Sarschar, Co-Founder & CTO of femCycle
TelemetryDeck is the right app analytics service for all medical device apps and app providers that process sensitive data in their apps. And, of course, for those who value ethics, data protection, and digital sovereignty.
For us, data protection isn’t a compliance task at the end of the process, but an architectural decision at the very beginning. We collect only what we truly need for further development - while still identifying which features help our users in their daily lives.
Mahja Sarschar, Co-Founder & CTO of femCycle