Get Cortisol+

What Cortisol+ does

Cortisol+ turns the biometrics your Apple Watch already collects into a continuous picture of your stress physiology. It reads heart rate variability (HRV), resting heart rate, and sleep stages from Apple Health, compares them against your personal baseline, and estimates your cortisol pattern throughout the day — when it peaks, when it recovers, and which habits move it. There's nothing to wear that you don't already own and nothing to mail to a lab.

Beyond the live score, the app correlates each night of sleep with your next-morning stress level, flags days when your pattern deviates from baseline, and includes guided breathing sessions (Zen mode) that use your Watch's HRV reading to show whether a session actually calmed your nervous system. See the full feature overview for details.

What you need

• An iPhone running iOS 17 or later. Cortisol+ is iOS-only.
• Any Apple Watch paired to that iPhone. Every model that records HRV and sleep works — no specific series required.
• Apple Health permissions. On first launch you grant read access to heart rate, HRV, and sleep. Wearing the Watch overnight gives the app its most useful data.

The core experience is free. A Premium subscription unlocks advanced trends, longer history, and deeper sleep–cortisol analysis.

How the cortisol estimate works

No consumer wearable can measure cortisol directly — cortisol is a hormone measured in saliva, blood, or urine. Cortisol+ instead builds an estimate from biometric proxies that research links to stress-axis activity: suppressed HRV, elevated resting heart rate, and disrupted sleep tend to accompany elevated cortisol. After a calibration period the app learns your personal baseline, so the score reflects your deviation, not a population average.

That means Cortisol+ is a pattern tracker, not a medical device. It won't diagnose Cushing's syndrome or adrenal insufficiency, and it's not a substitute for lab testing when a doctor recommends one — read how it works for the full methodology and its limits.

Your data stays yours

Biometric processing happens on your device. Health data is never sold or shared with advertisers, and cloud sync is opt-in only. The full details are in our privacy policy.