How to track fibromyalgia flares with a smartwatch: sleep, heart rate, HRV and a pain diary your doctor can use

Short answer

You can't measure fibromyalgia pain with a watch, and no app or wearable has been shown to predict a flare. What a watch can do is record the things that tend to move around flares — sleep, night-time and resting heart rate, HRV as your own trend, and how active you were — without you having to remember them on a day when remembering is hard.

The research behind this is small but consistent. In two wearable studies that included people with fibromyalgia, nights with a higher heart rate during sleep were followed by more painful days, on average. Older diary research found the same with sleep quality: a worse night, a worse next day. And after exertion, pain in fibromyalgia tends to rise more in the 8 to 72 hours afterwards than straight away — which is why the day that caused a flare is often not the day you feel it.

The practical setup is simple. Wear the watch at night. Keep a one-minute daily diary: pain, fatigue and sleep quality on a 0–10 scale, plus a few yes-or-no context lines (stress, a busy day, weather change, period, poor night). When a flare comes, look back one to three days, not just at today. After a few flares, see what tends to come first for you. Bring your doctor one page, not three hundred screenshots.

And if you have been told it's "just stress" or that you look fine, you were not imagining it. Fibromyalgia flares are a recognised experience that people can tell apart from their everyday symptoms.

Before you blame yourself, check what your body already recorded. A flare that seems to come from nowhere can be a flare that followed a short night, a heavier day or a stressful week two days earlier — and your watch may have recorded it.

Can a smartwatch tell you a fibromyalgia flare is coming?

No — not in the sense of a reliable warning. No watch, ring or app has been validated to forecast a fibromyalgia flare, and none measures pain. Pain is something only you can report.

What research does show is that some signals a watch records move together with next-day pain at the group level:

• Night-time heart rate. In a 2024 study, 66 people with fibromyalgia or chronic back pain wore a sensor for an average of 81 days. A higher heart rate during sleep was followed by more pain the next day — but more pain did not predict a higher heart rate the following night (Dudarev et al., 2024). Three of the authors work for the company that made the sensor, which is worth knowing. A 2025 study of 79 people with fibromyalgia, tracked for two weeks with a wearable and a three-times-a-day pain app, found the same direction: nights with a lower sleep heart rate were followed by days when pain improved, and nights with a higher one by days when it worsened (Hanuka et al., 2025).

• Sleep quality. In a classic diary study, 50 women with fibromyalgia rated their sleep and pain for 30 days. A night of poorer sleep was followed by a more painful day, and a more painful day by a poorer night — the two feed each other (Affleck et al., 199603226-5)).

These are averages across groups. They don't turn your watch into a flare alarm, and on any one night a higher heart rate can have many reasons — alcohol, a late meal, a warm room, an infection, your period. The honest use is different: over weeks, your own records can show whether your flares tend to follow certain nights or certain days. That is information you can act on and bring to a clinician.

What to track with fibromyalgia: the short list

Fibromyalgia trackers and printable journals often ask for twenty things a day. Most people stop within a fortnight. A short list you keep for months beats a long one you keep for a week. Here is what is worth recording, and what else moves each signal.

Sleep: wear the watch to bed

If you track only one thing with a device, make it sleep. Sleep problems are part of fibromyalgia itself — NHS lists difficulty getting to sleep or staying asleep among its main symptoms (NHS) — and sleep is where the strongest day-to-day link with pain has been found. Record total sleep, how many times you woke and, in your diary, how rested you felt on waking. A consumer wearable estimates sleep stages from movement and heart rate rather than measuring brain waves, so treat "deep sleep minutes" as a rough guide and wake-ups and total time as the more useful numbers.

Night-time and resting heart rate: compare you with you

Your watch calculates resting heart rate every day and records your heart rate overnight. Neither number means much on its own. What matters is whether this week sits above your usual range. Give it two to four weeks of normal life to learn your range. Our guide to normal resting heart rate with a chronic illness explains why your normal may not match a chart.

HRV: a personal trend, never a score against someone else

Heart rate variability (HRV) is the variation in time between heartbeats. As a group, people with fibromyalgia tend to have lower HRV than people without it: a systematic review found that most of the 10 case-control studies comparing fibromyalgia with healthy controls reported lower HRV and signs of higher "fight or flight" activity (Meeus et al., 2013), and a meta-analysis across chronic pain conditions found the effect was driven heavily by fibromyalgia studies (Tracy et al., 2016).

That is a group difference, not a test. For you, HRV is useful only as your own trend on the same device, measured the same way:

• Look at weeks, not mornings. HRV jumps around in everyone — see why HRV fluctuates day to day.

• Read it next to resting heart rate. Several days of HRV below your range while resting heart rate sits above it is a more meaningful pattern than either alone.

• Don't trust a "great" number on a terrible day. Welltory's help notes for chronically ill bodies point out that in some people with ME/CFS, POTS, long COVID or fibromyalgia, an unusually good-looking HRV reading can appear in the middle of a crash rather than during recovery (Welltory Help).

Steps and active time: look one to three days back

This is the signal people most often look at on the wrong day. A meta-analysis of exercise studies in ME/CFS and fibromyalgia found that pain after a standard exercise test rose more when it was measured 8 to 72 hours later than when it was measured within two hours (Barhorst et al., 2022). In everyday life that means the flare you feel on Thursday may belong to Tuesday's errands, a long drive or a day you finally felt well enough to clean the house.

A small preliminary look at Welltory Energy Lab data, published in our article on fibromyalgia flares, points the same way: among 8 members with fibromyalgia who had enough journal and wearable data, 7 had symptoms that tended to be more likely one to three days after a high-activity or high-stress day than on the day itself, each compared only with her own baseline. The difference was small — a few percentage points — and one member showed no delay at all. Eight people is an early observation from members' own journal entries and wearable data, not a clinical study, and it is not a feature of the Welltory app — but it is a reason to look back, not just at today. If movement is part of your treatment plan, our guide to exercising with fibromyalgia without triggering a flare covers how to build it up.

Stress, weather and your cycle: the context lines

When 44 people with fibromyalgia were asked what causes their flares, the main answers were stress, overdoing it, poor sleep and weather changes (Vincent et al., 2016). NHS also lists stress levels, changes in the weather and how physically active you are among the things that make symptoms better or worse (NHS).

Weather is a good example of why personal records matter. In a Norwegian study, 48 people with fibromyalgia reported pain three times a day for a month while weather data were collected in the background. On average, lower barometric pressure and higher humidity went with more pain, and stress made the pressure effect stronger — but 8 of the 48 reacted the opposite way (Fagerlund et al., 2019). A group finding may not be your pattern.

The menstrual cycle is less well studied in fibromyalgia. If you have periods, mark them in your diary for two or three cycles and compare; that is more useful than any general rule.

How to keep a fibromyalgia pain and flare diary that survives a bad week

A diary only helps if you still fill it in on the days you feel worst. Keep it to about a minute:

Every day, three numbers (0–10): pain, fatigue, and how rested you felt on waking. Same time each day, ideally evening.

Every day, five yes-or-no lines: stressful day; busier than usual (physical, mental or social — all three count); poor night; weather change you noticed; period day. Add one line that is personal to you if you already suspect something — a long drive, a migraine, a medication change.

On flare days, one more line: "flare: yes", with when it started and what helped, if anything did. A flare is a stretch that is clearly worse than your usual baseline; you are the judge of that, not the watch.

Once a week, two minutes: glance at the week's sleep, resting heart rate and HRV on your device next to your diary. Don't analyse; just notice.

Use whatever is easiest. Paper, a phone note, a spreadsheet or an app all work. The Arthritis Foundation offers a free printable fibromyalgia flare tracker if you prefer paper, and our activity and symptom diary guide has a layout built around energy and pacing.

Give it four to eight weeks. One bad day proves nothing. You need several flares in the record before anything that looks like a pattern is worth taking seriously.

How to spot what tends to come before your flares

This is the part where the watch earns its place. Not by warning you, but by remembering what you can't.

1. Learn your normal first. For the first two to four weeks, just collect. Note your usual sleep length, your usual resting heart rate range and your usual HRV range on ordinary days.

2. After each flare, line up the three days before it. Write down, for each of those days: hours slept and wake-ups, night or resting heart rate compared with your usual, HRV compared with your usual, steps or active time, and your context lines. It takes five minutes and is much easier with the data in front of you than from memory.

3. After three to five flares, compare. Is there something that keeps turning up? For some people it is two short nights in a row. For others, a resting heart rate a few beats above their normal for a couple of days, a big social weekend, or a stressful work deadline. For many, it is a mix — and some flares will have nothing obvious before them at all. Both are useful to know.

4. Look at the days that *didn't* flare, too. If short nights come before your flares but also before plenty of ordinary days, that is a weaker link than it looks. Pattern-hunting only on bad days is the easiest way to fool yourself.

5. Change one thing, then watch the trend. If something stands out, change one thing — protect sleep before a big day, spread errands across the week, plan a lighter day after a heavy one — and look at the next four to six weeks, not the next morning.

What you are building is a personal record of what tends to come first, to discuss with a clinician — not a rule and not a forecast. Patterns in your own data are links worth raising, not proof that one thing causes your flares.

What watch data can't tell you

• It can't measure pain. No sensor reads pain, stiffness, fibro fog or tenderness. Those come only from you.

• It can't tell what caused a change. A higher night heart rate can come from a flare, a cold, a glass of wine or a hot bedroom.

• It is less accurate during movement. Wrist sensors are reasonably good at rest and during sleep, which is where the useful fibromyalgia signals are. During activity, a Duke study found optical heart rate error was on average about 30% higher than at rest (Bent et al., 2020).

• It works in both directions. Pain disrupts sleep, and poor sleep worsens pain. A shifted number may be the flare showing up, not something that came before it.

• "Green" numbers can sit next to a terrible day. People with energy-limiting conditions often describe feeling awful on a day the watch scores as fine. Our piece on why your wearable and your feelings disagree explains why. Your body is the primary source; the watch is a second witness.

When tracking makes things worse

Tracking is meant to give you information and some control. For some people it becomes another source of stress: checking numbers many times a day, feeling worse after looking, cancelling plans on the strength of one reading. If that is happening, hide the live numbers, review your data once a week rather than every morning, and remember that the value is in the pattern over weeks. Our guide to health tracking anxiety goes further.

Before you blame yourself, check what your body already recorded

Most people with fibromyalgia know the feeling of a flare that seems to make no sense. You did nothing different today, and yet everything hurts, your thinking is thick and the fatigue is total. The obvious explanation seems to be you: not coping, getting weaker, overreacting.

The data can tell a less personal story. Two days ago there was a five-hour night. Or a family visit that meant hours of talking and being "on". Or a deadline week, a long car journey, the first cold front of autumn, the start of your period. Each of those can land in your body a day or two later, and many of them leave a trace you can look back at: a shorter, more broken night, a resting heart rate above your usual, HRV below it, a spike in steps.

That is the permission and the lever at once. You are not failing; there is often a reason, and it may already be in your watch. Change one thing and look at the trend over the next few weeks rather than the next morning.

How to show your flare data to your doctor

Appointments are short. The aim is something a clinician can take in at a glance.

Bring a one-page summary. Four to eight weeks of: your daily pain, fatigue and sleep-quality scores, flare days marked, average sleep and resting heart rate per week, and the context lines that turned up most often before flares.

Bring two or three flares in detail. For each: when it started, how long it lasted, what helped, and the three days before it.

Lead with the pattern, in plain words. "My flares usually start a day or two after a short night or a busy day, last three to five days, and are worse in the week before my period" is an opening a clinician can work with.

Say "my records show", not "my watch proved". It keeps the conversation on the evidence.

Mention anything new or different. New symptoms, symptoms that don't fit your usual flares, or flares that are getting more frequent are worth raising on their own, whatever your data shows.

When should you see a doctor?

See your doctor if you think you might have fibromyalgia and haven't been assessed — NHS advises seeing a GP, as treatment can ease symptoms (NHS). If you already have a diagnosis, book an appointment if flares are becoming more frequent or longer, if a flare feels different from your usual pattern, if your usual way of recovering stops working, or if new symptoms appear — such as joint swelling, fever, unexplained weight loss, or dizziness or a racing heart when you stand up.

Seek emergency care for chest pain or pressure, fainting, severe shortness of breath, or sudden weakness, numbness, trouble speaking or trouble seeing. These are not flare symptoms to wait out, and a watch reading is never a reason to delay.

How to bring this up with your doctor — and what to ask for

• "Here is a one-page summary of eight weeks of my pain, sleep and flare days. Does anything in this pattern change what we should try?"

• "My flares seem to follow short nights. Is it worth looking at my sleep more closely?"

• "Are there other causes we should rule out for the symptoms that don't fit my usual flares?"

• "What should I do differently in the first days of a flare, and what should make me call you?"

• "Would a referral to a pain management or physiotherapy service that understands pacing help?"

• "If we change a medication, what should I watch in my diary to see whether it's working?"

Living with fibromyalgia: the questions people ask next

Can fibromyalgia affect your heart rate?

Fibromyalgia isn't a heart condition, but research shows autonomic differences: as a group, people with fibromyalgia tend to have lower HRV and signs of higher sympathetic ("fight or flight") activity, and in two wearable studies a higher heart rate during sleep was followed by more pain the next day. Palpitations, or a racing heart and dizziness when you stand up, are not fibromyalgia symptoms to accept without checking — raise them with your doctor, as they can have other causes, including POTS.

Does weather affect fibromyalgia?

For many people, yes, though not for everyone in the same way. Weather changes are among the flare causes people with fibromyalgia name most often, and in a Norwegian study lower barometric pressure and higher humidity went with more pain on average — but 8 of 48 participants reacted the opposite way. Mark weather changes in your fibromyalgia diary and see whether your own flares follow them.

Do fibromyalgia flares change with my period?

Many people notice symptoms change around their period, but the menstrual cycle is not well studied in fibromyalgia. The practical answer is to track it: mark period days in your diary for two or three cycles and compare pain, fatigue, sleep and resting heart rate across the cycle. Bring what you find to your doctor, especially if the pattern is strong.

Why do I feel terrible when my watch says I recovered well?

Because a watch reads heart rate and movement, not pain, fatigue or fibro fog. In energy-limiting conditions, people often describe "green" recovery scores on their worst days, and an unusually good-looking HRV reading can even appear in the middle of a crash. With fibromyalgia, trust how you feel as the primary signal and use the watch as context, not as a verdict on whether you are allowed to rest.

What is the best app to track fibromyalgia?

There is no single best fibromyalgia tracking app, and no app is validated to predict flares. The best one is the one you will still use on a bad day. Look for a quick daily entry, a place to mark flares and context, automatic sleep and heart rate from your watch, and a way to export your data for your doctor. A paper tracker works too if that is easier.

How long does a fibromyalgia flare last?

There is no fixed length. In research, people with fibromyalgia describe flares as periods clearly worse than their everyday symptoms, and many say they cope partly by waiting them out. Some flares last days, others longer. Recording when each flare starts and ends in your fibromyalgia diary is the best way to learn your own typical length — we cover what helps in fibromyalgia flares: why they happen and what helps.

Should I keep exercising during a fibromyalgia flare?

Exercise is the one fibromyalgia treatment the EULAR guidelines recommend strongly (Macfarlane et al., 2017), but during a flare many people scale right down rather than push through. Agree a flare-day plan with your clinician or physiotherapist in advance. Your diary can show how long after a heavier session your symptoms tend to rise — see our guide to exercising with fibromyalgia without triggering a flare.

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How Welltory helps — and what it cannot do

Welltory is a general wellness app, not a medical device. It does not diagnose fibromyalgia, does not measure pain and cannot predict a flare. What it can do is collect your watch data in one place, show it against your own baseline, and help you keep the context around your hard days.

Which devices give what. According to Welltory's help center, an Apple Watch or Samsung Galaxy Watch can be used for both HRV and activity in the app; other smartwatches, fitness trackers and rings — including Garmin, Fitbit and Oura — usually send activity, sleep and heart rate through Apple Health, Health Connect, Samsung Health or a direct connection (Welltory Help).

Your nights, against your own normal. On iOS with an Apple Watch or Oura, Welltory's Sleep Analysis shows sleep stages, wake-ups and your night-time heart rate. Its help article notes that with fibromyalgia, a consistently elevated night pulse isn't necessarily one bad night — it can be part of your baseline, so the comparison with your own recent nights matters more than one night read alone (Welltory Help).

Your stress timeline, read for a body like yours. Welltory marks periods of raised heart rate without movement in orange and recovery in blue. The help center notes that with fibromyalgia, a resting heart rate that runs high can show as orange even without an emotional trigger, and real rest can register as orange — neither means the rest didn't count (Welltory Help). These zones describe your heart rate, not a condition.

Tag what was happening. When Welltory detects a stress or rest episode, it asks "What happened?" You can tap a suggested tag, type or say it: long drive, family visit, deadline, cold front, period day, short night. On iOS, My Patterns collects those tags and shows which situations recur around stress episodes, which help you recover, and which rare events your body reacts to strongly; insights typically need at least 7 occurrences of a tag in a month plus some history from the month before (Welltory Help). Daily notes, mood and how you feel physically can go in the Journal (Welltory Help).

Logging hard days. On iOS, Crash Tracker lets you record when a crash started — some people use it for flares, its severity, symptoms, what came before and what helped, and compares those days with your own baseline for active time, stress time and HRV. The charts cannot predict a crash or identify its cause. It is currently offered in English to new iOS users who reported ME/CFS or chronic fatigue, long COVID or POTS during onboarding; logging is free, the baseline charts need a subscription (Welltory Help). If you don't see it, the diary above and tags do the same job.

Take it to your doctor. In the Welltory web app, Dashboard → choose a chart → choose the dates → Export gives you a CSV of that chart's data (Welltory Help) — the raw material for your one-page summary.

Where to learn this with other people. If you want help reading your data alongside women with the same condition, Welltory Energy Lab is a paid, moderated community where Welltory's science team and Medical Board explain the group's data patterns in plain language (what it is and who it is for).

Patterns are links worth raising with a clinician, not proof of a trigger.

How we made it

Fibromyalgia symptoms, the factors that make them better or worse, and the advice to see a GP come from the NHS fibromyalgia pages. The flare causes people name come from a qualitative study by Vincent and colleagues (2016). Day-to-day links between sleep, night-time heart rate and next-day pain come from Affleck and colleagues (1996), Dudarev and colleagues (2024; three authors are employed by the sensor company, as the paper discloses) and Hanuka and colleagues (2025). The delayed rise in pain after exertion is from the Barhorst and colleagues (2022) meta-analysis; group differences in HRV are from the Meeus and colleagues (2013) systematic review and the Tracy and colleagues (2016) meta-analysis; weather findings are from Fagerlund and colleagues (2019); the strong recommendation for exercise is from the 2017 EULAR guidelines; the accuracy figure for optical heart rate is from Bent and colleagues (2020). All group findings are reported with their sample sizes and are not presented as personal predictions. The Energy Lab observation (8 members with fibromyalgia) is Welltory's own preliminary, aggregated analysis, previously published in our fibromyalgia flares article; it is not a clinical study. Welltory features are described only from Welltory's public help center (articles updated between December 2025 and October 2026). The emergency list is standard clinical triage rather than a quotation from any one source. The questions in the "questions people ask next" section reflect, in general terms, what people living with fibromyalgia and other energy-limiting conditions commonly ask about tracking; no individual's words or data are used.

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