Where does this reading come from?
Every metric is traced back to its source and device, so you can see which sensor, app, or Apple Watch produced it — and when.
A read-only HealthKit interpreter
Understand your Health data.
See where your Apple Health metrics come from, why they're missing, and what may help generate the next reading — explained in plain language, entirely on your device.
On-device · Read-only · No account · No cloud
Heart Rate Variability
Apple Watch · past 7 days
42ms
What the app tells you
- officialTime-domain variability recorded beat-to-beat while at rest.
- observedLower values may appear after poor sleep or high stress.
Illustrative sample data, not your data.
The story behind your numbers
Your Health app shows you numbers.
HealthLens shows you the story.
Why is it missing?
HealthLens walks through the likely recording conditions and shows the evidence behind each explanation — labelled by how certain it is.
What could create the next reading?
Clear, practical conditions for generating a fresh measurement — a 20-minute outdoor walk, a night with your watch on, no guesswork.
Nineteen metrics, decoded
Every number, explained.
HealthLens covers the metrics Apple Health tracks — each with its own detail page, trend chart, and source inspector. Three are free; sixteen more unlock with Pro.
Free Always available
- Heart Rate VariabilityBeat-to-beat variability of your resting heart rhythm.
- Resting Heart RateYour lowest heart rate while at rest, typically measured during sleep.
- Respiratory RateBreaths per minute, mostly recorded overnight by your watch.
Pro One-time unlock · no subscription
- Cardio Fitness (VO₂ Max)Estimated aerobic capacity from outdoor walks, runs, or hikes.
- Cardio RecoveryHow quickly your heart rate settles after a workout.
- Walking Heart Rate AverageAverage heart rate during steady outdoor walks.
- Blood OxygenOxygen saturation readings from your wrist sensor.
- Wrist TemperatureSkin temperature tracked overnight while you sleep.
- Walking SteadinessBalance and stability estimates from everyday walks.
- Running PowerPower output during runs, measured at the wrist.
- Step CountDaily steps recorded by iPhone, Apple Watch, or compatible sources.
- Active EnergyDaily energy burned through physical activity and exercise.
- Exercise TimeDaily full minutes at or above brisk-walk intensity.
- Walking + Running DistanceDaily distance accumulated while walking or running.
- Sleep DurationNightly asleep time with overlapping stages merged.
- WeightLatest body-mass measurement from Apple Health.
- Body Mass Index (BMI)Latest saved BMI value and its trend.
- Body Fat PercentageLatest saved body-fat percentage and its trend.
- Water IntakeDaily water total from manual or compatible sources.
A metric may have no data, be stale, or never have been generated — HealthLens tells you which, and why.
Missing-data diagnosis
“Why is there no data?” — answered with evidence.
When a metric is missing or stale, HealthLens reviews the recording conditions — watch presence, workout type and duration, heart-rate context — and presents each explanation with an evidence grade, so you always know how confident it is.
- officialDocumented by Apple
- observedSeen in your data
- possibleA likely explanation
- unknownCannot be confirmed
Missing
Cardio Fitness (VO₂ Max)
No readings in the last 30 days.
Possible explanations
Privacy by architecture
Your health data stays on your device. Full stop.
HealthLens was built around a simple constraint: it should never need to see your data leave the device. There is no server to upload to, no account to attach data to, and no analytics to feed.
- Read-only access
- HealthLens never writes, edits, or deletes anything in Apple Health. It only asks to read.
- No account, no profile
- There is no sign-up, no login, and nothing to link your health data to.
- No cloud, no upload
- Nothing is sent to a server. Health samples exist only in memory, for as long as a feature needs them.
- No analytics, no tracking
- No analytics SDKs, no cross-app or cross-site tracking, no advertising, no data sold — ever.
- No AI training
- Diagnosis runs on-device with a transparent rule-based engine. Your data is never used to train models.
One-time unlock
HealthLens Pro.
A single purchase unlocks every metric, the Workouts tab, and the Workout Inspector — with full trends, diagnosis, and source history. No subscription, ever.
$9.99 one-time · lifetime unlock
Everything, unlocked:
- Cardio Fitness, Cardio Recovery, Walking HR Average
- Blood Oxygen, Wrist Temperature, Walking Steadiness, Running Power
- Steps, Active Energy, Exercise Time, Walking + Running Distance
- Sleep Duration, Weight, BMI, Body Fat Percentage, Water Intake
- Missing-data diagnosis with evidence grades
- Workouts tab + Workout Inspector (last 30 days)
- Full historical trends (7D · 30D · 6M · 1Y)
- Data Source Inspector — last 30 days, up to 50 samples per source
Purchases are processed and stored by Apple through the App Store.
Questions, answered
Good questions.
Is HealthLens a medical device?
No. HealthLens is a health-data interpretation tool. It does not provide medical advice, diagnosis, treatment, or emergency monitoring. Status labels and explanations may be incomplete — always consult a qualified professional for health decisions.
Does HealthLens write to Apple Health?
No. HealthLens requests read-only access and never adds, modifies, or deletes information in Apple Health. You stay in control of every permission.
Is my health data uploaded anywhere?
No. There is no account, no developer-operated server, and no analytics SDK. Health samples are processed in memory on your device only and are never persisted or uploaded.
What does HealthLens Pro include?
Pro unlocks the sixteen remaining metrics, the Workouts tab, and the Workout Inspector — including full trends, missing-data diagnosis, and the Data Source Inspector. It is a one-time purchase, not a subscription.
Why is my VO2 Max not updating?
VO₂ Max is estimated during outdoor walks, runs, or hikes of at least 20 minutes while wearing your Apple Watch. If none of those workouts happened recently, Apple Health won't generate a new estimate — HealthLens shows you exactly which condition is missing.