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Your Daysy data can do more
Meet Ona, your AI-powered menstrual health expert. Ona connects directly with your Daysy fertility tracker and combines every basal body temperature reading with your symptoms, daily logs, and wearable data — to uncover patterns that are easy to miss, even in a doctor's office.
Ona
Reading your Daysy data
Your temperature confirms you ovulated on Day 15 — and your 13-day luteal phase sits right in the healthy range.
Day 15
Ovulation
13 days
Luteal
+0.6°F
Temp shift
A menstrual health app built with leading experts
Ona is a menstrual and hormonal health app for iOS and Android, made in collaboration with Lara Briden, ND — the naturopathic doctor and bestselling author of Period Repair Manual and Hormone Repair Manual. If you found your way to fertility awareness through her work, you already know the philosophy behind Ona.
At its core, Ona is a conversation. Ask it anything — why you're spotting mid-cycle, what new facial hair might mean, why your luteal phase feels different this month — and it responds with personalized, expert-reviewed answers grounded in peer-reviewed research. When you share a concern, Ona guides you through a clinician-like assessment designed to understand your full health picture and uncover root causes, not just label symptoms.
of women experience period pain
An estimated 70% of PCOS cases go undiagnosed, and more than half of women report feeling their health concerns weren't taken seriously. Ona exists so you never again have to hear that severe pain, irritability, or fatigue are “just part of being a woman.”
Why your Daysy data deserves a second life
Basal body temperature is one of the most underrated vital signs in women's health. Daysy — the hormone-free fertility tracker made in Germany by Valley Electronics — uses it to determine your fertility status with an intelligent algorithm built on a database of 10 million menstrual cycles.
menstrual cycles behind Daysy's intelligent algorithm
accuracy identifying non-fertile (green) days
cycles from 5,328 women in the published study
van de Roemer et al., 2021
That same temperature curve also reflects whether you ovulated at all, how robust your luteal phase is, and whether stress, travel, or an underlying hormonal condition is shifting your cycle. Ona treats ovulation as a vital sign of overall health — it affects metabolism, brain function, and long-term wellbeing. Which is why Ona's guiding principle is simple: don't suppress your cycle, understand it.
What happens when you connect Daysy to Ona
Ona imports your Daysy readings automatically — no transcribing numbers — then analyzes your temperature patterns alongside everything else it knows about your cycle: your logged symptoms, lab results, sleep, and activity data. From there, Ona can:
Daysy captures the signal with medical-grade precision. Ona interprets it in the context of your whole health picture — a set of personalized insights neither data source could produce alone.
How the Daysy + Ona integration works
Connecting the two takes only a few minutes.
- 1
Keep measuring with Daysy
Under your tongue, first thing in the morning, before getting out of bed.
- 2
Download Ona
Get Ona from the App Store or Google Play and create your free account.
- 3
Connect Daysy
In Ona's integrations section, connect Daysy to import your temperature readings automatically.
- 4
Add context
Log symptoms, complete an assessment, or sync Apple Health or Health Connect for sleep and activity data.
Ona's period tracking is completely free. Advanced features — unlimited conversations with the AI and fully personalized insights — normally cost $19.99 per month or $169.99 per year, and Daysy users get 50% off. Don't have a Daysy yet? Learn more at daysy.me.
More than a period tracker
Daysy answers one question with remarkable precision: am I fertile today? Ona picks up where that answer ends, supporting women across the full spectrum of cycle-related conditions.
Painful periods and PMS
Identify the triggers and patterns behind monthly symptoms.
PCOS
Understand your PCOS type and track what actually moves the needle.
Endometriosis
Document pain patterns that support faster diagnosis and better conversations with your doctor.
Perimenopause
Make sense of changing cycles with insights tailored to this transition.
Coming off the pill or trying to conceive
Navigate the return of your natural cycle and prepare for pregnancy with data, not guesswork.
PMDD, hormonal acne, irregular or missing periods
And more. These aren't marketing categories — they're the reasons women come to Ona.
One user spent years being told her pain was normal before Ona helped her identify the patterns that led to her endometriosis diagnosis. Another used Ona to navigate coming off the pill and preparing for pregnancy. A third made sense of a PCOS diagnosis that arrived just as perimenopause began. Different stories, one thread: data plus context equals clarity.
Backed by experts, built for privacy
Ona's content and AI are continuously reviewed by a team of clinicians, and its proprietary AI is grounded in peer-reviewed research and updated as the science evolves.
Lara Briden, ND
Naturopathic doctor and bestselling author of Period Repair Manual and Hormone Repair Manual, and a member of the scientific advisory council for the Centre for Menstrual Cycle and Ovulation Research at the University of British Columbia.
Katarzyna Bednarska, MSc
Clinical nutrition and functional medicine specialist with more than a decade of experience in hormone-related care.
Jarek Oleszczuk, MD, PhD
Physician and healthcare executive.
Privacy works the way it should: your data is securely stored, never sold to third parties, and you can delete it entirely at any time. For anyone who chose Daysy partly because it's a hormone-free, body-literate approach to cycle tracking, Ona's privacy-first, physiology-first philosophy will feel familiar.
Ona + Daysy — questions & answers
Does Ona work with the Daysy fertility tracker?
Yes. Ona connects directly with your Daysy fertility tracker and imports your basal body temperature readings automatically, so your daily measurements feed straight into Ona's analysis.
Do I still need Daysy if I use Ona?
Yes — they do different jobs. Daysy is a dedicated medical-grade fertility tracker that determines your daily fertility status from precise basal body temperature measurements. Ona is the interpretation layer: it uses that data, plus your symptoms and history, to explain what is happening with your hormones and health. Together, they are stronger than either alone.
Is Ona free?
Ona's period tracker is entirely free. Premium AI features are subscription-based, and Daysy users get 50% off.
Which devices does Ona support?
Ona is available for iPhone on the App Store and for Android on Google Play, and integrates with Apple Health, Health Connect, and Daysy.
Start decoding your cycle today
You've already done the hard part: building a daily habit of measuring your basal body temperature. Ona makes every one of those measurements work harder for you. Download Ona, connect your Daysy, claim your 50% discount, and unlock what your cycle has been trying to tell you.
Explore Daysy at daysy.me.
Statements about Ona have not been evaluated by the FDA or any other health agency. Ona is not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare provider about your health.