Clair's Wrist Device Tracks Hormones Continuously Without Blood Tests

Hormones are foundational drivers of metabolism, sleep, cognition, cardiovascular health, and aging — yet they remain invisible to virtually every consumer wearable on the market. Clair Health is attempting to change that with a noninvasive wrist-worn device designed to continuously track estrogen, progesterone, luteinizing hormone, and follicle-stimulating hormone in women. The San Francisco startup has closed a seed round bringing total funding to $11.6 million, led by Khosla Ventures with participation from a16z speedrun.

The core insight driving Clair's technology is that existing wearables already collect signals — heart rate variability, skin temperature, respiratory rate, sleep patterns — that are shaped by hormonal fluctuations, but lack the interpretive layer to make sense of them. Clair claims its device uses 10 biosensors and more than 130 proprietary features processed through AI models to infer hormonal activity continuously, without any form of sampling.

Perhaps the most striking claim from beta testing is that female physiology may involve nine distinct hormonal sub-phases rather than the four phases conventionally taught. If validated, this would represent a meaningful revision of how female biology is understood — with direct implications for timing nutrition, exercise, recovery, and therapeutic interventions across the lifespan.

For longevity medicine, the implications are substantial. Perimenopause is one of the most consequential and least-monitored biological transitions women undergo, associated with shifts in cardiovascular risk, bone density, cognitive function, and metabolic health. Continuous endocrine tracking could enable earlier detection of hormonal change, better-timed interventions, and more individualized care during this window.

However, significant caveats apply. The device is pre-commercial, and independent clinical validation of its hormonal inference accuracy has not yet been published. The nine sub-phase finding is intriguing but unverified. Regulatory clearance pathways and clinical utility in real-world settings remain to be demonstrated before this technology can be considered a reliable health tool.