Ona + Daysy: Turn Every Morning Temperature Into Deeper Hormonal Insight

At Ona, we believe your cycle is a vital sign, and that ovulation is one of the clearest windows into your overall health. But insight is only as good as the data behind it. Symptoms tell us how you feel. Lab results tell us a snapshot in time. Basal body temperature tells us, morning after morning, what your hormones are actually doing. That is why we built a direct integration with Daysy. As a bonus, connecting Daysy gets you 50% off Ona.

Why Basal Body Temperature Is Such Powerful Data

You could track BBT with any thermometer and a notebook, but measurement quality makes or breaks temperature data. Daysy is a dedicated fertility tracker built around a highly precise sensor designed specifically for basal body temperature tracking. Unlike conventional thermometers, it waits for your temperature to fully stabilize (about 60 seconds) rather than estimating an instant reading, which eliminates one of the biggest sources of error in manual BBT charting.

That small shift carries big information. It confirms you actually ovulated, not just that an app predicted you would. It shows how long your luteal phase lasts, which reflects progesterone production. Tracked over months, it reveals patterns: delayed ovulation from stress or travel, anovulatory cycles hiding behind "regular" bleeding, or the growing irregularity of perimenopause. This is exactly the kind of objective, day-by-day signal our AI needs to separate real trends from noise.

Meet Daysy: The Gold Standard of At-Home BBT Measurement

You could track BBT with any thermometer and a notebook, but measurement quality makes or breaks temperature data. Daysy is a dedicated fertility tracker built around a highly precise sensor designed specifically for basal body temperature tracking. Unlike conventional thermometers, it waits for your temperature to fully stabilize (about 60 seconds) rather than estimating an instant reading, eliminating one of the biggest sources of error in manual BBT charting.

Behind the sensor sits a self-learning algorithm built on a database of over 10 million menstrual cycles and 40 years of fertility awareness research. In a published study of 5,328 women and more than 107,000 cycles, Daysy determined the non-fertile (green) days with 99.4% accuracy. Each morning, Daysy shows your fertility status in seconds: a green light means not fertile, red means fertile or possibly fertile, and a flashing red light marks your predicted ovulation day. It is hormone-free, intuitive, and designed to eliminate user error, the same values that guide how we build Ona.

Ona Health

What Happens When You Connect Daysy to Ona

Once connected, Ona automatically imports the basal temperature readings from your Daysy, no manual charting, no transcribing numbers into an app. Your temperature curve then joins everything else Ona knows about you: your logged symptoms, assessment conversations, lab results, and sleep and activity data from Apple Health or Health Connect.

That combination is where the magic happens. With verified temperature data in the mix, Ona can:

Confirm ovulation objectively instead of relying on calendar predictions alone.
Spot luteal phase patterns and connect them to symptoms you log, like PMS, spotting, or sleep changes.
Detect early red flags, such as repeated anovulatory cycles, that are worth raising with your doctor.
Sharpen period and ovulation predictions as it learns your unique patterns.
Give you a clear, data-backed summary to bring to medical appointments.

In short: Daysy captures the signal with medical-grade precision, and Ona interprets it in the context of your whole health picture.

How to Connect Your Daysy to Ona

Open Ona and go to the integrations section.
Select Daysy and follow the pairing instructions.
Keep measuring as usual, under your tongue each morning, before getting up.
Watch your insights get richer as temperature data flows in automatically.

Don't have a Daysy yet? Explore the Daysy fertility tracker. And if you already own one, connecting it to Ona takes just a few minutes — and earns you 50% off Ona's premium features.

Ona Health App

Who Gets the Most Out of This Integration

Coming off hormonal birth control, see when real ovulation returns, not just when bleeding resumes. Trying to conceive naturally, combine Daysy's fertile window with Ona's guidance on cycle health. With PMOS, formerly PCOS, irregular cycles make ovulation confirmation especially valuable, since bleeding alone doesn't prove you ovulated.

In perimenopause, track how your cycles are actually changing instead of guessing, and connect unexplained symptoms like fatigue, mood shifts, or spotting to specific cycle phases with objective data. Because ovulation affects metabolism, brain function, and long-term wellbeing, knowing whether and when you ovulate is valuable even if you're not trying to conceive.

Your cycle is a monthly report card on your health, Daysy helps you read the temperature line, and Ona reads the whole report.

FAQ

Do I need a Daysy to use Ona?

No. Ona works fully without one, you can log symptoms, run assessments, and sync Apple Health or Health Connect. But high-quality BBT data from Daysy meaningfully deepens the insights our AI can give you.

Does Ona replace the DaysyDay app?

They serve different purposes. DaysyDay is Daysy's companion app for fertility statistics. Ona uses your temperature data for something broader: understanding your hormonal health, uncovering root causes of symptoms, and answering your questions, reviewed by experts including Lara Briden, ND.

How do I claim the 50% discount?

Connect your Daysy in Ona's integrations section and the discount is applied to Ona's premium subscription.

Is my data private?

Yes. Your data is securely stored, never sold to third parties, and you can delete it entirely at any time.

Ready to Put Your Mornings to Work?

Sixty seconds with Daysy every morning. A lifetime of understanding with Ona. Connect the two today, claim your discount, and let every temperature reading bring you closer to answers about your hormones, your cycle, and your health.

Download Ona on the App Store or Google Play, and explore Daysy at daysy.me.