How Vitality Tracker works, in full.

Getting started

Setup takes a few minutes. Before you rely on a single number, VT shows you what your devices can give it and what they cannot.

1. Install Vitality Tracker from the App Store or Google Play and create your account.
2. Allow access to Apple Health or Health Connect. VT asks once for everything it can use. Leave out anything you prefer not to share; the parts of the app that need it will tell you.
3. Connect the services you use. Oura, Withings, Polar and Google Health each take one sign-in. The VT Longevity Pro Scale and the Polar H10 pair over Bluetooth, from inside the app.
4. See what you have. VT checks what each source actually delivers, lists what is there and what is missing, and suggests how to fill the gaps.

Three ways in. You do not need a wearable to get started, and a thirty-dollar scale with an entry-level band is a complete setup. VT opens on the screen that suits what you own.

Fasting, meal planning, supplements and shopping lists work on every path. Add a device whenever you like, and VT starts using it straight away.

Start from a baseline

Nothing on this page requires a blood test or a glucose sensor; a scale and a band are a complete start. But if you are serious about your health, two things in your first month make everything VT does afterwards sharper, and we recommend both.

A baseline lab panel. One blood draw, taken before you change anything, gives VT the markers its computed indices and the Vitality Score are built from, PhenoAge, FIB-4, the Systemic Immune-Inflammation Index, HbA1c and your lipids among them, and it fixes the point every later result is measured from. VT’s recommended panel is one most GPs can order and most laboratories run from a single visit: see the recommended baseline panel →. Upload the report and Eir files each result under its panel for you to confirm.

A month on a continuous glucose monitor. Two sensors, about four weeks, worn while you eat, train and sleep as you normally do. A month of readings shows how your body handles your own meals, fasts and nights, which no population chart can tell you, and gives VT a measured starting point for your metabolic health rather than a questionnaire’s guess. Expect at least one food to behave nothing like you assumed; the founder’s was oats. Sibionics GS3, FreeStyle Libre 2+ and Ottai connect today, and the Dexcom is on its way.

With both in place you have a baseline, and a baseline is what turns the months that follow into evidence. Every Playbook target, every regimen and every change you make can be read against where you started, so you see what VT’s recommendations and your own interventions are doing rather than hoping.

If a result needs a doctor’s eye. When your baseline comes back, VT marks any result outside the laboratory’s own reference range and, if there are any, suggests a consultation. There are two ways to have one. Take your pre-visit report, which carries the results, your history and the questions worth asking, to your own GP. Or book a private video consultation with a doctor who works with Vitality Tracker, a functional-medicine physician who knows how VT’s reports are built, for a set time that is yours alone, with no travel and no waiting room. Members on a paid plan book at the member rate; during the invitation-only beta the member rate applies to everyone.

Your devices, your choice

Most health apps are built around one brand of device. VT is built the other way round: it reads all of your devices and lets each part of the app use the one that measures it best.

One source leads. Your primary source supplies the everyday readings: heart rate, resting heart rate, HRV, blood oxygen, steps and active calories. It is usually the device you wear all day, whatever that is.

Any part of the app can use a different source. Trust your ring for sleep and your band for everything else? Choose exactly that. You do not have to pick one device and lose what the other does well.

Each one is set to Automatic until you change it. With one wearable there is nothing to choose: VT uses it everywhere.

Every device by name, with what it can and cannot do. The source lists name the device itself, your watch or your ring, not just "Apple Health". Each shows what that device can provide, such as "Full" or "No daytime HRV", and when it last sent data. You choose knowing what you will get.

VT pulls the health store's mix apart. Apple Health and Health Connect merge every device into one figure. VT works out which device took each reading, so your sleep comes from your ring, not from a blend of ring and watch. An old watch in a drawer can be switched off, so it is never read by accident.

One device, two routes, counted once. Oura can reach VT directly and through Apple Health. Connect both if you like; VT will not count anything twice.

Where your data comes from

Data reaches VT three ways: straight from the maker's service after one sign-in, through your phone's health store, or over Bluetooth from the device itself. A direct connection usually carries more than the health store does, so VT connects directly wherever it can.

Everything else, through your health store. VT reads whatever reaches Apple Health or Health Connect, from any brand. Another make of watch or ring, a blood-pressure cuff or a food diary all count. If it writes to your health store, VT can use it.

VT gives back, too. Your scale's weigh-ins, your glucose readings and the meals, blood pressure and water you log are written to Apple Health or Health Connect, so your other apps see them as well. VT never changes what your other devices recorded.

What the health stores leave out

A health store only holds what each maker chooses to write into it, and many write less than their own app shows. If a reading never reaches Apple Health or Health Connect, VT cannot see it.

That is why VT connects directly wherever a maker allows it, and why setup tells you what is missing and how to get it. When a reading is missing, VT shows a dash and says why. It never fills the gap with a guess.

Same night, different detail

Two devices can record the same night and hand over very different amounts of it. One takes a reading every five minutes, another a few spot readings, and a chest strap records every heartbeat. VT shows you what each one gives, rather than presenting every source as if it were the same.

The method is on every reading. SDNN and RMSSD measure HRV differently and give different numbers for the same heart. VT labels each HRV figure with its method, so you never compare one with the other by mistake.

You can see what is behind a number. The night's heart-rate and HRV charts give the count of readings, with the average, lowest and highest. A figure built on 96 readings and one built on four are not the same thing, and VT does not pretend they are. Glucose works the same way; see how often readings arrive, under Continuous glucose.

Synthetic data. The two charts share one y-axis; the difference is how much of the night each source recorded.

Sleep: two scores, two questions

VT scores your sleep two ways, because "how was last night?" and "how healthy is my sleep?" are different questions. You choose which one leads; with the Sleep Health Index leading, last night's score still sits in the rings.

The index rewards a steady rhythm. Going to bed and waking at the same times carries the most weight, and an irregular pattern pulls the whole index down. Restoration comes from you: one tap each morning on how well you slept.

Sleep stages are drawn, not scored. Consumer devices cannot yet tell deep from REM sleep reliably enough to grade a night on. VT shows your stages in full and leaves them out of the score. The Night Log adds your own record of the night: one tap for in bed, awake, toilet break, back in bed and up for the day, shown over your device's stages in the morning so you can see which wakings it caught and which it missed.

Your device's own score stays its own. With Oura or Polar as your sleep source, VT shows their nightly score. VT scores the night itself only when they have not, or after you correct your sleep times, and it says so.

Nothing is hidden. If a reading the score normally uses is missing, VT names it next to the score. Naps are shown and counted in your day's total sleep, but never scored. The full scoring method, with every weight, curve and limitation, is published on the Methods page.

Continuous glucose

A continuous glucose monitor shows how your body handles each meal, fast and night. VT puts those readings next to everything else it knows about you.

Vitality Tracker is not affiliated with Abbott, and the LibreLinkUp route depends on a service Abbott may change.

The live dashboard. One trace through your whole glucose history, with your meals, fasts and sleep marked on it. Scroll back to any day and see what you ate and how you responded. Alongside it: daily average, morning fasting glucose, estimated HbA1c, time in range and how much of the day the sensor covered.

Sensors, tracked for you. Start a sensor in VT and note where it is worn: arm, abdomen or thigh. VT keeps its warm-up readings out of your figures and reminds you 12 hours before it expires. Some people read differently on each side; recording the spot is how you find out.

Bad readings are caught. A failing sensor can report glucose moving ten times faster than a body can. VT spots it, tells you to check your sensor, and lets you take that stretch out of your averages. Nothing is deleted; it just stops counting.

Notifications that respect your attention. A high-glucose notification comes only when glucose has stayed above the threshold you set for 15 minutes and is still high, one per episode rather than a stream. Low notifications are off unless you switch them on, because VT cannot promise to wake you. VT does not replace your sensor's own alarms.

How often readings arrive. With a Libre 2+, it depends on your phone. Two-minute readings catch the spike after a meal that a 15-minute history smooths away.

Your readings are also shared to Apple Health or Health Connect, so your other apps can use them. No wearable? A CGM on its own is a complete start: VT opens on your Glucose dashboard.

The VT Longevity Pro Scale

The VT Longevity Pro Scale measures your weight and full body composition, and it talks to VT directly over Bluetooth. There is no second app and no extra account.

What it measures. Weight, body fat, muscle, water, bone and visceral fat, with each arm, each leg and your torso measured separately.

Built around you. Body composition depends on who is standing on the scale. VT sends your sex, age and height to the scale, so every reading is calculated for you. Update your profile and the scale gets the change. The scale's own derived figures, basal metabolic rate, metabolic age and a weight target, are replaced by VT's: the same energy calculation the energy engine uses, VT's own metabolic age, and your Weight Goal where you have set one.

Step on, and that is it. VT listens for the scale whenever it is running, in the background too. Your reading appears on the Body Composition screen within seconds. Keep your phone nearby: a weigh-in VT does not hear is not imported later.

One honest reading a day. Weigh in as often as you like. VT takes your lowest full reading before noon as the day's figure, the closest thing to a like-for-like morning weigh-in. A false start in socks, followed by a proper reading, is tidied away for you.

What you get from it: the Body Composition screens, with a body map, charts, trends and a PDF report; Metabolic Age, which needs body fat as well as weight; a daily energy figure built on your real body composition rather than a population average; and your weight and body fat in Apple Health or Health Connect. Had a DEXA scan? Add the result and VT calibrates the scale's body-fat reading to it. Scale readings shift with hydration, so read the trend rather than a single morning. No wearable needed: with the scale alone, VT opens on Body Composition.

Polar H10 chest strap

A chest strap reads your heart's electrical signal, beat by beat. During exercise that is far more accurate than any watch, ring or band, and it records every interval between beats, which is what HRV is made from. VT works with the Polar H10 alongside any wearable, over Bluetooth, with no Polar account needed.

It stands in for your wearable when you wear it. Turn on Use chest strap data, and wherever the strap was worn its readings replace your wearable's: live heart rate and HRV on Today while it is on your chest; every beat of a workout, with an HRV chart, and zones, splits, energy and training load worked out from the strap; the night's heart-rate and HRV charts when the strap covered at least half the night. Everything the strap supplies is marked "via H10". Take it off and Today switches back to your wearable within seconds.

It records by itself. Start a workout in VT and the strap records it. Use Night Log, and tapping In bed starts a night recording that ends when you are up for the day. You can also record by hand at any time.

See how your wearable really did. A workout shows the strap's heart rate under your wearable's, so you can see where your watch or band kept up and where it fell behind. The strap's recordings stay on the phone that made them; they are not uploaded to your account.

What the engines do

VT's engines learn what is normal for you, then read every new night against that personal normal rather than against population averages. They run on VT's platform, behind the app, and update every time the app sends in your latest data.

• Symptom Radar notices when several of your overnight readings sit outside your usual range at the same time, a sign your body is under strain.
• Symptom Trend reads how fast those readings are moving, a sudden jump or a slow drift.
• Daily energy expenditure works out how many calories you really burn, from your weight and what you eat.
• Vitality Score sums up five areas of metabolic health in one number.
• Blood-pressure measures turn your readings into two figures that describe your arteries.

Because every engine learns from you, each needs some history before it can say anything, and its results become more reliable the longer you use VT. The nightly sleep score, the Sleep Health Index and Capacity, your overnight recovery, are computed in the app itself and are described in Part 1.

The basics

You are compared with yourself. A resting heart rate of 62 can be ordinary for one person and high for another. VT first learns your usual range for each reading, then looks for changes against it.

Learning your normal takes time. Some engines work from your first reading; others need several weeks of history. Early results are marked provisional and firm up as your history grows.

Your normal keeps moving with you. The engines look back over a rolling window, usually your last 30 days, so they follow gradual changes in your fitness, routine or season.

Results update when the app syncs. The engines run each time the VT app sends in your latest data. Open the app in the morning so last night's readings are counted.

A gap is not a zero. A night or day with no data is simply left out. Gaps slow an engine down, but they never count against you.

Symptom Radar

Each morning, Symptom Radar compares last night with your own normal and tells you whether your body looks settled or under strain. Its first result arrives on your seventh morning, as long as at least three readings sync every night.

Readings that usually move together are counted once, so one change is never counted several times. That leaves five independent signs: your heart (overnight and daytime heart rate, HRV), your sleep, your breathing rate, your temperature and your blood oxygen.

Your daily result. Normal: everything sits within your usual range. Yellow: a few readings sit outside it; consider easing off training and prioritizing rest. Red: several readings sit well outside your usual range and agree with one another; rest is strongly advised, and if you feel unwell, speak to a healthcare professional. Red normally needs several signs to agree. Two things can turn a day red on their own: blood oxygen below 94%, or one reading far beyond anything in your recent history that nothing you logged explains. VT also holds fixed floors, such as blood oxygen below 90%, whatever your normal is.

When the first result appears. Each reading needs 7 usable nights within the last 30 days before it can be scored, and Symptom Radar starts once three readings reach that mark. Until then, the app shows how many nights are still needed. If fewer than three readings are arriving after your first week, the status changes to Not enough data; waiting will not fix this, so check that your devices are syncing.

How confidence grows. Week 1: building your baseline, with a countdown of nights. Week 2, provisional: results appear but are marked provisional while VT is still learning your ranges; a provisional day cannot go red on its overall score, though it can still go red for low blood oxygen, one extreme reading, or two independent signs both far outside range. From about day 14, once at least half of your readings have 14 nights behind them, results stop being provisional. Around day 30, each reading's normal is built from a full month of nights and is at its most reliable. Each result also carries a confidence label: High when at least two core overnight signs were measured, Medium when one was, Low when none were, results are still provisional, or a reading you usually have is missing.

What it takes into account. Some everyday things move your readings without any strain behind them. When you log them, Symptom Radar gives the affected readings less weight: hard training, measured against your own training goal; alcohol, scaled by how much you drank; a late bedtime, a late meal or a large late meal; high soreness the evening before; your period. "Late" and "large" are judged against your own habits, and VT needs about 20 logged examples in the last 90 days before it can tell what is unusual for you.

Symptom Trend

Symptom Radar asks whether last night was unusual; Symptom Trend asks how fast things are changing. It is fully switched on about five weeks after you start, provided you record most nights. It reads two patterns: a jump, where a reading changes from one night to the next by more than it normally does for you, and a drift, where a reading creeps steadily in one direction over several days with no single night standing out.

Symptom Trend builds on Symptom Radar's nightly results, so it cannot start until Symptom Radar has, and it never raises a day above yellow; red stays with Symptom Radar alone. Drift reading starts once about two weeks of nights have been scored. Jump reading needs 28 pairs of back-to-back scored nights for at least one reading, about four weeks from Symptom Radar's first result. Only unbroken pairs count: a missed night breaks the pair on either side of it, and a day you mark as unwell spoils both pairs it belongs to, because those nights are not your normal.

Daily energy expenditure

This engine works out how many calories you really burn in a day, your total daily energy expenditure. It combines two estimates and trusts whichever is on firmer ground: from your body, a starting estimate from your age, sex, height, weight and, where available, body composition, using the best of seven published formulas for your data; and from your record, what you ate set against how your weight actually changed. If you eat 2,500 kcal a day and your weight holds steady, you burn about 2,500 kcal. The longer you log, the more the result rests on your own record rather than on a formula, and the result is always a range with a confidence level, never a single number.

When the first result appears. The engine needs 29 days with both weight and calories logged in the last 36 days. Logging one without the other does not count, and because older days roll out of that window, a gap early on can push your first result back by more than the days you missed.

How confidence grows. It depends on how much you have logged, about three weeks of dense logging for high; whether your weight is steady, since a stable weight with consistent eating gives the most reliable result; how recently things changed, because when you start losing or gaining, the engine needs about two weeks to settle on the new pattern and waits five days before deciding a change is real, so one big meal does not reset it; and whether your food log and your weight agree, because a consistent disagreement suggests some food is going unlogged.

What it takes into account. Some days make the scale less trustworthy, and VT gives them less weight: alcohol, short sleep, no bowel movement, a hard training session, your menstrual cycle, and the first weeks of creatine. Days you mark as a planned break from your usual eating are left out. The full method is published on the Methods page.

Vitality Score

The Vitality Score sums up your metabolic health as one number from 0 to 100, built from five areas. It can appear from your first day, once your profile is complete and two of the three core areas have a measurement.

Blood sugar, body composition and fitness are the core areas. The headline score needs at least two of them, plus your height, sex and date of birth. If an area has no data, the score is shared across the areas you do have, and each area's own score is still shown. Days you mark as unwell pull the lifestyle area down for that week.

Measurements have a shelf life. Some are taken daily, others a few times a year. Each counts in full while it is fresh, is still used for a while after, then drops out until you measure again.

An HbA1c estimated from a glucose sensor lasts as long as a lab result only when the sensor covered at least 70% of the 90 days behind it; with less coverage, it ages faster. If your weight and habits have held steady, VT can keep a lab HbA1c for up to 180 days and a waist measurement for up to 90 or 180 days, and while it does, the score's confidence is shown as low and VT prompts you to measure again.

Confidence. High: at least four areas measured, all fresh, and 20 or more days of data. Medium: at least three areas, no more than one past its fresh period, and 7 or more days. Low: anything less, or a measurement kept past its usual shelf life.

Blood-pressure measures

From the age of 50, VT turns each day's blood pressure into two figures that describe your arteries, and they appear from your very first reading. Mean arterial pressure is the average pressure pushing blood through your arteries across a heartbeat. Fractional pulse pressure is how large each pulse is compared with that average; over time it reflects how flexible your arteries are.

The rules: age 50 and over only, with your date of birth in your profile, because in younger people the pressure measured at the arm differs too much from the pressure near the heart for the figure to mean much; one value a day, from the average of all that day's readings; and each new value is compared with the average of your previous seven, with a change of less than 2% counting as stable. Your blood pressure also feeds the arteries area of the Vitality Score, at any age.

Timeline at a glance

If every reading and log arrives daily from day 1, Symptom Radar gives its first result on day 7 and stops being provisional on day 14. Energy expenditure follows on day 29, and Symptom Trend is fully on by day 36. Each missed day pushes the later milestones back by at least a day, and a missed weight or food log can push energy expenditure back further.

What to be aware of

The engines are only as good as the data behind them. Most surprises in the first weeks come from one of these.

Switching devices. Different devices measure sleep differently: in one member's records, a stand-in device reported 15 minutes of deep sleep against the usual hour from their regular one, while both agreed on total sleep. VT therefore ties your sleep readings and overnight heart rate to the device that records them. A one-off swap, such as wearing a watch while your ring charges, is set aside for that night; you still get a result, with lower confidence. A real switch is accepted after the new device has recorded 7 nights in a row, and VT then rebuilds your sleep normal from the new device, so those readings are missing from your results for about a week. Alternating devices from night to night keeps resetting this: choose one device for your nights and stay with it. Breathing rate, blood oxygen and temperature can also shift when the device changes, so expect a few unsettled days after any switch.

Missed measurements. A missed night is skipped, not counted as a bad one, though missed nights in the first weeks push your first results back. A reading you usually have but is missing tonight makes the result partial: it is marked low confidence and is more cautious, needing two signs to agree before showing yellow. For energy expenditure, a day counts only if both your weight and your food are logged. After a month without a reading, VT starts learning your normal for it again from scratch.

Results can update during the day. Some data reaches VT later than the rest; daytime heart-rate averages, for example, are only complete at the end of the day. When late data arrives, VT recalculates the affected days, so a morning result can change by the evening.

Days you feel unwell. Only you can mark a day as unwell; VT never does it for you. Those days, and the three days after, are kept out of your normal, so your recovery does not distort what VT expects next time. Remember to untick the day when you feel better.

Everyday context. Alcohol, a late or large evening meal, high soreness, hard training and your period all move overnight readings. VT can allow for them only when they are logged, and the training allowance also needs a training goal set in the app.

Getting the most out of VT

A few habits in your first month make every engine faster and more reliable.

1. Complete your profile: date of birth, sex and height. The Vitality Score, the energy formulas and the blood-pressure measures all need them.
2. Wear the same device every night and let it sync each morning.
3. Open the app each morning, so last night's data is counted.
4. Weigh yourself every morning under the same conditions, and log everything you eat. Energy expenditure needs both on the same day.
5. Measure your blood pressure at least weekly. A reading stays fresh for 7 days.
6. Keep periodic measurements current: waist every two weeks, VO₂ max monthly, HbA1c every three months.
7. Mark the days you feel unwell, and untick them when you recover.
8. Log the everyday context: alcohol, your last meal, soreness and your period, and set a training goal.
9. Be patient. Symptom Radar starts in your first week and is fully confident after about two. Energy expenditure and Symptom Trend take four to five weeks.

What is coming

The third question, trajectory, is the one the engines above do not yet answer: has your physiology settled at a new level, when, by how much, and across how many systems? The Trajectory Layer we are building will look for that, week by week, on the same family of change-point tests used in the research literature, and will give you a one-page summary your doctor can read in a minute. Until it ships, Level and Velocity are what VT reads.

Not a diagnosis

Vitality Tracker describes and tracks physiological measures recorded by your own consumer devices against your own history, for general wellness and for discussion with a health professional. It tracks measures, not disease, and does not diagnose, predict or monitor any disease. If you feel unwell, speak to a healthcare professional, whatever your results say.