Can a smart ring track your health in real time?

Three kinds of “real time”

• A reading when you ask. You open the app and see your pulse now.
• A running record. The ring measures through the day and night, and you see the trend later.
• An alert. The device tells you something without being asked. This is the part the rules care about most.

What a ring measures, and when

Movement is cheap to sense, so a ring follows it all the time: that is how it counts steps and tells sleep from waking. The pulse is read by shining light into the finger, and that signal is easily disturbed when the hand moves, which is why the study that found one ring accurate for heart rate and the common HRV figure against a chest ECG measured at night (what HRV is). A light that shines often also costs battery: in our own design model, a heart sensor that wakes through the night shortens a ring’s charge noticeably (the trade-off). Skin temperature means most as a change from one night to the next.

The line between wellness and medicine

In January 2026 the FDA replaced its 2019 guidance on general wellness products. It may now treat a wearable that uses non-invasive sensing, such as light, to estimate blood pressure, oxygen saturation, blood glucose or heart rate variability as a wellness product, if those numbers are for wellness alone. Such a product may show values, ranges, trends, baselines and summaries over time, and relate them to sleep, activity, stress and recovery. It may not:

• refer to specific diseases, clinical conditions or diagnostic thresholds;
• raise alerts or alarms that call for medical action, or give treatment advice;
• claim clinical accuracy or medical grade, or present itself as a stand-in for an authorized medical device;
• show numbers that look like clinical values unless the maker has validated them.

It may tell you that a professional’s opinion could help when a value falls outside the range for wellness use, as long as the message names no disease, does not call the value abnormal and is not ongoing monitoring of a condition. A product meant to screen for, diagnose, monitor or alert you to a disease is a medical device; the guidance names blood pressure monitors, glucose meters, continuous glucose monitors and ECG recording and analysis among them. A glucose wearable whose micro-needles pierce the skin falls outside the wellness policy even when it makes only wellness claims.

What that means for you

• Not reviewed. The FDA does not intend to examine low-risk wellness products; the maker is expected to validate numbers that look clinical.
• A nudge, not a diagnosis. A suggestion to see a professional is worth acting on, and symptoms count more than any number.
• Emergencies. If you feel seriously unwell, call your emergency number, 112 across Europe, whatever a ring shows.
• In Europe the line is drawn by intended purpose: under the EU’s Medical Device Regulation, what a maker says a product is for, in its instructions and in its advertising, decides whether it is a medical device.

What we are working on

The first Lychnos Ring has no health sensors. For a later model we are working on wellness trends from heart rate, heart rate variability, skin temperature and sleep, presented as wellness insights: your own baseline and how it changes over weeks, with no diagnosis and no alarms about illness. It is in development: why our first ring skips health.

Sources, read 4 November 2026: US Food and Drug Administration, general wellness: policy for low risk devices, guidance, 6 January 2026; Cao and colleagues, accuracy assessment of Oura ring nocturnal heart rate and heart rate variability in comparison with electrocardiography, Journal of Medical Internet Research, 2022. General information, not medical advice.