Ambulatory ECG (24-hour Holter monitor) (Ambulatory electrocardiogram (Holter monitor))
A small, portable monitor worn for 24 hours or longer to record the heart's electrical activity during everyday life, used to capture symptoms or rhythm changes a short ECG might miss.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- A Holter monitor records your heart over 24 hours or longer during normal life, to catch rhythm changes or symptoms a short ECG might miss.
- It is most useful when symptoms happen often enough to occur while you are wearing it; a normal recording can simply mean nothing happened that day.
- It is usually not painful and low-risk; the main practicalities are keeping it dry and pressing the event button and keeping a diary when you have symptoms.
- Results come after the recording is downloaded and analysed, and are interpreted alongside your symptom diary.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your specialist will give you advice for your situation.
Records the heart over a longer period than a short ECG, improving the chance of catching the problem
Infrequent symptoms unlikely to occur within a few days, where an event-triggered or implantable recorder is a better choice.
You carry on with normal activities, keep the monitor dry (unless it is a device designed to be removed to wash), and press the event button and note your...
Clear instructions on using the event button and diary, and on returning the device.
You carry on with normal activities, keep the monitor dry (unless it is a device designed to be removed to wash)...
At the end of the recording period you return the monitor to the clinic. The electrodes are removed and the skin...
The recording is downloaded and analysed by a physiologist and reported, usually by a cardiologist. This takes...
Your referring clinician explains what the recording showed alongside your symptom diary, and what happens next –...
What is an ambulatory ECG (24-hour Holter monitor)?
An ambulatory ECG, often called a Holter monitor, is a small portable device that records your heart's electrical activity continuously over a period of time – commonly 24 hours, 48 hours, or up to about a week. A few sticky electrodes on your chest connect to a small recorder you clip to your waistband or carry in a pocket, while you go about your normal day.
It is used when a standard resting ECG, which lasts only a few minutes, might miss the problem. Because many heart-rhythm symptoms come and go, recording over a longer period gives a much better chance of capturing palpitations, an abnormal rhythm, or the cause of dizziness, blackouts or breathlessness. You usually keep a diary of your symptoms so they can be matched to the trace.
A Holter monitor gathers information; it does not treat anything. It is most useful when symptoms happen often enough to occur during the recording. If your symptoms are rare, the test can be normal simply because nothing happened while you wore it, and a longer or different type of monitor may be suggested.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Holter monitor compared with a resting ECG
| Feature | Holter monitor | Resting ECG |
|---|---|---|
| How long it records | 24 hours to about a week | A few minutes |
| Where | At home, during normal life | In clinic, lying still |
| Best for | Symptoms that come and go | A snapshot of rate and rhythm |
| Symptom diary | Yes – you note symptoms | Not usually needed |
| Limitation | Misses symptoms that don't happen while worn | Misses anything not happening at the time |
If your symptoms are infrequent, even a few days of monitoring may not capture them, and a longer-term or event-triggered recorder may be more useful.
Preparing for your test
- Wear a top that buttons or is loose, so the electrodes and recorder are easy to fit and conceal.
- Have a wash or shower before your appointment, as you usually cannot get the monitor wet once it is on.
- Avoid heavy moisturiser, oil or talc on your chest, as electrodes stick better to clean, dry skin.
- Some chest hair may need trimming so the electrodes stay attached during the recording.
- Plan to keep your normal routine during the recording, so it captures a typical day; ask if there is anything to avoid.
- Tell the team about your symptoms, your medicines, and any pacemaker or implanted device.
- Make sure you understand how to use the symptom button and diary, and how and when to return the device.
What happens
At the clinic, a cardiac physiologist cleans the skin and attaches a few sticky electrodes to your chest, connected by short wires to a small recorder that clips to your waistband or sits in a pocket. Fitting usually takes around 10–15 minutes and includes a chance to ask questions.
You then go home and carry on with your normal activities. Whenever you notice a symptom – such as palpitations, dizziness or breathlessness – you press the event button and write the time and what you felt in a diary. This lets the team match your symptoms to what your heart was doing at that moment.
Most 24- and 48-hour monitors must be kept dry, so you cannot shower or bathe while wearing them; some 7-day devices can be briefly removed to wash, using fresh electrodes. When the recording period ends, you return the device to the clinic, where the data is downloaded and analysed before a report is produced.
Is this test right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- Infrequent symptoms unlikely to occur within a few days, where an event-triggered or implantable recorder is a better choice.
- As a way to 'rule out' all heart-rhythm problems, since it only records while worn.
- Where symptoms are clearly brought on by exertion and an exercise test would be more appropriate.
- As a substitute for emergency assessment when symptoms are severe or sudden.
Delay or rearrange if…
- You are acutely unwell and need emergency assessment rather than a routine test.
- You have a skin condition or wound on the chest that would prevent electrodes attaching safely.
- A water-based activity you cannot avoid clashes with a device that must stay dry – timing may need adjusting.
- You do not yet understand how to use the event button and diary, which are key to a useful result.
Alternatives to discuss
- A longer-term or patient-activated event recorder for infrequent symptoms.
- An implantable loop recorder for rare but important episodes such as unexplained blackouts.
- A resting or exercise ECG, depending on the symptoms.
- An echocardiogram or blood tests to look for other causes.
- Review by a clinician to decide which test, if any, is needed.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Records the heart over a longer period than a short ECG, improving the chance of catching the problem
- Lets your symptoms be matched to your heart rhythm using the event button and diary
- Can help diagnose causes of palpitations, dizziness, blackouts or breathlessness
- Done at home during normal activities, so it captures a typical day
- Usually not painful and non-invasive, with no needles or radiation
Risks & complications
- Mild skin redness, itch or irritation under the electrodes
- The inconvenience of keeping the monitor dry and not showering for 24–48 hours
- Needing some chest hair trimmed so the electrodes stay on
- A normal recording if no symptoms happened while you wore it
- An electrode coming loose, leaving a gap or poor-quality section in the recording
- A non-diagnostic recording that needs to be repeated or extended
- Picking up a minor or unrelated finding that leads to further tests
- Skin reaction to the adhesive in people with sensitive skin
- False reassurance if symptoms are infrequent and simply did not occur during the recording
A Holter monitor is usually not painful and carries essentially no physical risk – it only records, and gives no electricity. The main limitations are practical (keeping it dry, electrodes staying attached) and diagnostic: it can only catch problems that happen while you are wearing it. If your symptoms are infrequent, ask whether a longer-term or event-triggered recorder would be more likely to capture them, and what happens if the recording is normal but your symptoms continue.
Published figures to discuss
An ambulatory ECG is usually not painful and carries essentially no physical risk, so meaningful complication rates do not apply; the important figures are about how well it captures the problem rather than harm. Its usefulness depends on whether your symptoms happen while you are wearing it – the more often they occur, the more likely the monitor is to record them, so a normal result can simply mean nothing happened that day. The diagnostic yield varies widely with how frequent the symptoms are and how long the device is worn.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Physical harm from wearing the monitor | No significant physical risk; minor skin irritation can occur | The monitor records signals only. Adhesive sensitivity or itch from electrodes is the usual side effect. | NHS – Electrocardiogram (ECG)nhs.ukSource-linked context |
| Missing an intermittent rhythm problem | Recognised; more likely when symptoms are infrequent | A normal 24-hour Holter does not rule out arrhythmia if symptoms did not happen during recording. Longer patch monitoring or an implantable loop recorder may be needed. | Guide sourcesClinical context |
| Incidental ectopic beats or benign rhythm findings | Common practical issue | The key question is whether symptoms match the rhythm finding. Extra beats without symptom correlation are often not the explanation. | Guide sourcesClinical context |
| Poor-quality recording | Recognised | Loose electrodes, water exposure, poor diary detail or electrical interference can reduce diagnostic value. | Guide sourcesClinical context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is no physical recovery from wearing a Holter monitor. What matters afterwards is that the recording is downloaded and analysed, matched to your symptom diary, and explained to you with a clear plan.
- No physical after-effects from wearing the monitor
- Slight redness or itch where the electrodes were attached
- Some inconvenience from keeping the device dry during the recording
- Waiting days to weeks while the recording is analysed and reported
- Being asked for a repeat or longer recording if symptoms did not occur or the trace was unclear
Aftercare
- Return the monitor and your completed symptom diary as instructed, as the diary is key to interpreting the recording.
- You can return to normal activities and wash normally once the monitor is removed.
- If the skin is irritated where the electrodes were, a simple moisturiser usually helps.
- Make sure you know who will report the recording and when and how you will get the result.
- Ask what the result means alongside your symptoms and whether further monitoring or tests are needed.
- Keep noting your symptoms while you wait for results, in case they help with the next step.
- Seek urgent help if you develop severe chest pain, fainting or sudden breathlessness, rather than waiting for the report.
- A wash or shower before fitting, as you usually cannot get the monitor wet
- Loose or buttoned top to conceal the device
- Understanding of how to use the event button and diary
- A note of your usual medicines and any implanted device
- Knowing when and where to return the monitor and diary
- Knowing who reports the recording and when results are due
- Awareness of which symptoms need urgent care
⚠ Get urgent help if…
- Severe or spreading chest pain, or chest pain with sweating, sickness or breathlessness – call 999
- Fainting or blacking out, or nearly doing so
- Sudden or severe breathlessness
- A very fast, very slow or irregular heartbeat while feeling unwell, dizzy or faint
- Sudden weakness, numbness or difficulty speaking (possible stroke) – call 999
- A severe skin reaction under the electrodes, such as blistering or spreading rash
- Any symptom your clinician told you to treat as urgent
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your specialist gives you.
Results & realistic expectations
A useful result is a good-quality recording that captures a typical period of your daily life, ideally including an episode of your symptoms, so the team can see what your heart was doing at the time. Matching your diary to the trace is often what makes the test informative.
A normal recording is reassuring but mainly tells you that nothing abnormal happened while you were wearing the monitor – it cannot rule out a problem that simply did not occur that day. If your symptoms are infrequent, a normal Holter may lead to a longer-term or event-triggered recorder rather than a firm all-clear. Your clinician will explain what the recording can and cannot tell you.
A Holter recording reflects the period you wore it, so its value is tied to what happened during that time. If your symptoms change, recur, or did not occur during the recording, the test may need repeating or extending, or a different monitor may be used. Any diagnosis made from it is interpreted alongside your ongoing symptoms.
Related tests, treatments or support
A Holter monitor is often used alongside a resting ECG, an echocardiogram (heart ultrasound), blood pressure monitoring or blood tests, and is frequently arranged as part of a cardiology assessment. For symptoms brought on by exertion, an exercise ECG may be used instead or as well. Your clinician will explain which combination suits your situation.
Follow-up & long-term care
After you return the device, the recording is downloaded, analysed and reported, which takes time. Your referring clinician then explains the findings in the context of your symptom diary and what happens next – reassurance, treatment, or further monitoring or tests. You should be told who to contact if you do not hear back or your symptoms change in the meantime.
Repeat, follow-on and what comes next
- If no symptoms occur during the recording, it may need to be repeated or extended, or a different monitor used.
- A loose electrode or poor-quality section can mean a recording has to be redone.
- A normal recording with continuing symptoms usually leads to further monitoring rather than a stop.
- Findings are interpreted alongside your symptom diary and other tests, not in isolation.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- Clear instructions on using the event button and diary, and on returning the device.
- Interpretation of the recording alongside your symptom diary, not the trace alone.
- A sensible plan for repeat or longer monitoring if symptoms did not occur.
- Clear information on who reports the recording, when you get results, and which symptoms need urgent care.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- The length of monitoring (24 hours, 48 hours or up to about a week)
- The type of device used (standard Holter, patch monitor or longer-term recorder)
- Who downloads, analyses and reports the recording, and how quickly
- Whether it is arranged as part of a consultation or as a stand-alone test
- The facility or clinic where it is fitted and read
- Any further tests the result leads to, charged separately
- The fee for the monitor and how long it records
- Whether analysis and a written report are included
- Whether it is part of a consultation fee or charged separately
- How quickly the result and report will be available
- The cost of a repeat or longer recording if the first does not capture symptoms
- The cost of any further tests if the recording is abnormal
- The cancellation policy
On the NHS? Ambulatory ECG monitoring is available on the NHS when clinically indicated; private monitoring may be used for speed or as part of a cardiology assessment.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Treating a normal recording as proof there is no rhythm problem, when symptoms may simply not have occurred.
- Not explaining how important the event button and symptom diary are to a useful result.
- Not telling you who reports the recording and when you will get the result.
- Not setting out what happens if the recording is normal but symptoms continue.
- Not clarifying which costs are extra in private care, including reporting and any repeat recording.
Marketing red flags
- Offering a monitor as a way to 'rule out' all heart-rhythm problems.
- Not matching the length of monitoring to how often your symptoms actually happen.
- Selling monitoring as part of a package without clinical interpretation in context.
- Implying a normal recording is a complete all-clear regardless of symptom frequency.
Choosing a specialist safely
- Check the specialist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good specialist will welcome every one of these.
- Is a 24-hour, 48-hour or longer recording best for how often my symptoms happen?
- How exactly should I use the event button and diary?
- What happens if I don't get symptoms while wearing it?
- What will a normal or abnormal recording mean for me?
- Who will report the recording, and when and how will I get the result?
- If this does not capture my symptoms, what would the next step be?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the specialist who carries out my test, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this test not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Can I shower or bathe while wearing the monitor?
Will it get in the way of my normal day?
What if I don't get any symptoms while wearing it?
Is wearing a Holter monitor safe?
When will I get my results?
Is a Holter monitor available on the NHS?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: British Heart Foundation – Electrocardiogram (ECG) and ambulatory monitoring NHS – Electrocardiogram (ECG) University Hospitals Sussex NHS Foundation Trust – Ambulatory ECG monitoring British Cardiovascular Society – information for patients Mayo Clinic — Holter monitor
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
Related guides: Electrocardiogram (ECG) · Cardiology consultation · Echocardiogram (heart ultrasound) · Event recorder or implantable loop recorder · Exercise tolerance test (treadmill test)