The questions everyone is asking their wearable to answer
Pull up what people actually type into Google about their WHOOP or Oura and a pattern jumps out. The top questions aren’t about steps or workouts — they’re medical: Can WHOOP detect blood pressure? Can it test blood sugar? Can it tell if I’m getting sick? Can it catch heart problems?
That’s worth taking seriously, because it means millions of people are quietly hoping a $200–$400 band is doing physician-grade monitoring. This week made the question sharper: Oura was just hit with a class-action lawsuit over the accuracy of its sleep tracking — a reminder that the gap between what wearables market and what they measure is now a legal question, not just a nerd debate.
So here’s the honest sorting: what these devices genuinely measure well, what they estimate loosely, and what they cannot do no matter what the app implies.
What wearables measure well
Heart rate and heart-rate variability (HRV). Optical heart-rate sensing at rest is genuinely good on modern devices, and resting HRV trends are a legitimate window into recovery and nervous-system load. Accuracy degrades during intense, jerky exercise — but overnight and resting readings are solid.
Trends over time. This is the real superpower. Whether a single night’s “sleep score” is precise matters less than the trend: your resting heart rate drifting up over two weeks, your HRV sagging under stress, your overnight temperature deviating from baseline. Wearables are excellent change detectors on their own baseline — which is also why illness often shows up in the data before symptoms (elevated resting HR, suppressed HRV, temperature deviation). Not a diagnosis; a genuinely useful early flag.
Activity, steps, and consistency. Unglamorous and reliable — and behaviorally, the tracking itself drives real habit change.
What wearables estimate — with real error bars
Sleep stages. Here’s the uncomfortable truth at the center of the Oura lawsuit: wrist and finger devices don’t measure sleep — they infer it from movement, heart rate, and temperature. Against polysomnography (the electrode-based lab standard that actually reads brain waves), consumer devices are decent at detecting asleep vs. awake but substantially less accurate at staging — deep and REM assignments disagree with the lab a meaningful share of the time. Your “22 minutes of deep sleep” is a model’s guess, not a measurement. Trend it; don’t treat single-night stage numbers as lab data.
Calories burned. Estimates with wide error bars — often off by 20% or more. Fine for relative comparison, poor for meal-planning math.
SpO2 (blood oxygen). Useful for spotting patterns (and worth mentioning: repeated overnight desaturation flags are a reason to ask a physician about sleep apnea) — but not a medical-grade pulse oximeter.
What wearables cannot do — the part that answers the actual questions
Blood pressure: no. WHOOP’s “Blood Pressure Insights” feature (beta) offers an estimate that requires calibration with a real cuff, and it explicitly isn’t a medical device. No current mainstream wearable measures blood pressure. If BP matters for you — and it’s one of the most consequential numbers in all of medicine — a validated $40 cuff outperforms every band on the market.
Blood sugar: no. No wearable band measures glucose. Non-invasive optical glucose monitoring remains unsolved at consumer scale. Real glucose data means a fingerstick or a CGM (a small sensor with a filament under the skin — a different product category, and for non-diabetics an occasionally useful experiment rather than a necessity).
Diagnosing heart problems: mostly no. Some watches offer single-lead ECG that can flag possible atrial fibrillation — genuinely valuable, and worth showing a physician if it fires. Beyond that specific feature, a wearable cannot rule heart disease in or out. Chest symptoms beat any green dashboard, every time.
Diagnosing anything, formally. Every one of these products is a wellness device, not a medical device, and their fine print says so. That’s not a dodge — it’s the accurate description of what the sensors can support.
Where the actual data lives
The things a wearable can’t measure are, awkwardly, most of the things that matter clinically — and they’re all measurable by other means. Blood pressure needs a cuff. Glucose and insulin need a blood draw. Thyroid, iron, inflammation, and lipids need a panel.
That’s why the wearable conversation and the blood-testing conversation have converged this year: the same companies now sell both. If you’re weighing those panels, I compared them in WHOOP vs Function vs Blueprint — and once you have results in hand, how to read your blood test results covers what the numbers actually mean.
How to actually use a wearable well
- Trust trends, not absolutes. Your baseline vs. your deviation is signal; a single night’s stage breakdown is noise.
- Let it prompt questions, not answer them. Rising resting HR for two weeks is a great reason to look at stress, sleep, alcohol, or to see a clinician — not a diagnosis of anything.
- Pair it with the measurements it can’t make. A real BP cuff, periodic labs, and — if daytime sleepiness or snoring is your story — an actual sleep evaluation. (Wearable “sleep scores” cannot detect sleep apnea reliably; a home sleep study can.)
- Don’t let the score gaslight your body. If the app says you’re recovered and you feel wrecked — or the reverse — your body wins the argument. There’s even a name for wearable-induced sleep anxiety (orthosomnia); if the score is stressing your sleep, the score is the problem.
Frequently asked questions
Can WHOOP measure blood pressure?
No — its Blood Pressure Insights feature is a calibrated estimate in beta and not a medical device. Use a validated cuff for real readings.
Can a wearable test blood sugar?
No band currently measures glucose. That requires a fingerstick or a continuous glucose monitor.
Can WHOOP or Oura tell if I’m getting sick?
Sometimes, indirectly — elevated resting heart rate, suppressed HRV, and temperature deviation often precede symptoms. Treat it as an early flag to rest and watch, not a test result.
How accurate is wearable sleep tracking?
Good at asleep-vs-awake, meaningfully less accurate at deep/REM staging versus lab polysomnography — the gap behind the current Oura lawsuit. Use stage data as a trend, not a truth.
Should I stop wearing one?
No — they’re excellent trend detectors and habit tools. Just match your trust to what the sensor actually measures, and take medical questions to medical instruments and clinicians.
The takeaway
Wearables are superb at trends on your own baseline and legitimately useful as early-warning flags. They do not measure blood pressure, don’t touch blood sugar, guess at sleep stages, and diagnose nothing. Wear one, use the trends — and when the question is medical, use medical tools: a cuff, labs, a sleep study, and a clinician who reads them in context.
Want your wearable trends read alongside actual labs — what the band sees and what it can’t? Book a consultation in Tustin or virtually.
Author: Dr. Brandon Bright, DAOM, LAc — Tustin, Orange County. Educational content; not medical advice. Wearables discussed are wellness devices, not medical devices; blood pressure, glucose, cardiac symptoms, and suspected sleep disorders require appropriate medical evaluation. Details accurate as of August 2026.