Perimenopause may be one of the most universally shared experiences among women — yet ironically, it is one of the least understood and least measured.

Cycles start to shift.
Sleep becomes unpredictable.
Stress response changes.
Mood feels different.
Energy fluctuates.
Bones remodel faster than before.

And through all of it, most women ask:

“Am I actually in perimenopause… or is something else going on?”

That question is far more important than it sounds.

Because once perimenopause begins, it influences nearly everything:

Now for the first time, a mainstream health app is attempting to decode this transition with actual data.

Natural Cycles — best known as the first FDA-cleared birth control app — has officially launched NC° Perimenopause, a new mode designed to interpret hormonal shifts using biometrics, temperature trends, symptom logs, and cycle irregularities.

Women have been asking for this kind of clarity for decades.
And the early reaction is that this may be one of the most important updates Natural Cycles has ever released.

Most people assume perimenopause begins when cycles become irregular.

But in reality:

Physiological changes begin 2–8 years before your period noticeably changes.

That includes changes in:

Traditional healthcare relies heavily on:

And that lack of clarity often leaves women confused or dismissed.

NC° Perimenopause attempts to fill this gap by using something women already have access to:

daily biometric data.

Instead of relying on cycle changes alone, NC°’s new algorithm interprets:

Not just isolated temperatures — but long-term trending data from wearables.

Shifts in RHR often precede cycle changes.

Low or unstable HRV is common during hormonal transitions.

Perimenopause disrupts deep + REM sleep long before cycles change.

When cycles shorten or lengthen beyond normal variability.

Night sweats + hot flashes logged directly by the user.

Patterns tied to sleep, stress, and cycle timing.

Triggers like alcohol, stress, or exercise intensity.

This information feeds into Natural Cycles’ new
NC° Menopause Algorithm,
which attempts to determine where a woman is on the perimenopause timeline…

Early stage (subtle physiologic changes)
→ Mid stage (cycle instability + symptom intensity)
→ Late stage (leading toward menopause)

It’s not a diagnosis.
It’s not a medical determination.
But it is a structured interpretation of biometric patterns.

That alone is groundbreaking.

Perimenopause is confusing by design.
It is not:

It is a phased hormonal transition with peaks, valleys, and significant variability.

Having an algorithm that says:

…can be incredibly validating.

Many women using NC° have said the same thing:

“I finally feel like I’m not guessing anymore.”

And even though NC° is not a replacement for medical evaluation, hormone testing, or clinical care, it does provide the kind of clarity women have never had before.

This is one of the most important connections of all.

Perimenopause is the beginning of the bone-loss decade — not the end.

Here’s what the research shows:

This is when silent bone weakening begins.

These patterns are measurable in NC°.

The rollercoaster is more damaging than menopause itself.

Cycle length is a surprisingly useful marker.

Because you can’t feel bone density changes.

Knowing where a woman is in the perimenopause timeline becomes a powerful tool for:

At OsteoStrong, we’re not treating hormones — but we are helping women protect their bones, muscles, and nervous system during this transition.

And ILM Aesthetics & Wellness provides the clinical care that beautifully complements this.

Natural Cycles fills in a missing piece: clarity about where a woman is in her hormonal journey.

Women using NC° may be able to recognize trends that help guide:

Again: NC° doesn’t tell women what to do.
It tells them where they are.

And that alone can drive better choices.

There are now three emerging categories:

Measures vasomotor symptoms and autonomic patterns.

Interprets biometrics to identify perimenopause stage.

Helps distinguish hormonal signals from daily-life noise.

Together, these aren’t replacements for medical care…
but they are the beginning of a new era where women’s physiology is measurable.

For the first time:
Women don’t have to wonder.
Women don’t have to guess.
Women don’t have to feel dismissed.

Visibility replaces confusion.
Data replaces self-doubt.
Patterns replace frustration.

And that is long overdue.

In Part 3, we’ll explore the Withings × Clue partnership — the tool designed to tell women:

“This is hormonal”
vs.
“This is just stress, sleep, or life happening.”

This is the most precise bio-signal interpretation we’ve seen yet, and it could become an invaluable companion for women navigating strength training, bone-building, and longevity.

1. Natural Cycles Press Release (PR Newswire)
“Natural Cycles Launches NC° Perimenopause to Decode Hormonal Shifts” (Oct 14, 2025)

2. NaturalCycles.com — NC° Perimenopause Mode Overview
Description of algorithm, feature set, and biometrics.

3. Cycle Matters (Natural Cycles Blog)
“Introducing NC° Perimenopause”
Breakdown of temperature/HR/HRV analysis.

4. NAMS + WHO Menopause Data
Statistics on symptom onset and bone turnover during perimenopause.

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