Phira’s new wearable tracks hormone patterns from behind the ear

Phira is bringing hormone tracking to an unlikely place: behind the ear.

The women’s health startup has unveiled a small wearable that replaces a standard earring back and is designed to continuously track patterns associated with estrogen, luteinizing hormone (LH), and progesterone throughout the menstrual cycle. It works with most earring posts and is built to be worn around the clock, including while sleeping.

How Phira works

Unlike a blood or urine test, Phira doesn’t directly measure hormone concentrations. Instead, the wearable continuously collects thermoregulatory signals from behind the ear and uses those patterns to follow changes associated with key reproductive hormones.

The discreet wearable sits behind the ear and is designed to be worn throughout the day and night.

The location is intentional. Phira says the area behind the ear provides a stable place to capture subtle changes in body temperature and heat regulation, with sensors accurate to 0.03°C. The device is water-resistant, has a multi-week battery life, and is designed to stay out of the way during everyday activities.

That continuous data feeds into Phira’s platform, where users receive daily insights into their cycle, fertility window, and overall hormonal patterns. The company says the platform is also designed to help women understand how sleep, stress, training, and nutrition interact with their cycle and hormonal health over time.

From the lab to everyday wear

Phira tested the wearable in an IRB-approved pilot study covering 31 menstrual cycles across 12 women, comparing its data with daily urine-based hormone testing and other validated health-tracking tools. The company says signals captured behind the ear showed patterns consistent with established estrogen, LH, and progesterone dynamics throughout the cycle.

Separately, Phira’s foundational research on physiological sensing from the earring-back wearable was peer-reviewed and presented at the IEEE Engineering in Medicine and Biology Conference in July 2026. The company is now running a larger study across a broader group of women.

Where to get it

Phira has opened its waitlist for early access and plans to launch commercially in 2027.