DVT (blood clot in the leg) assessment (Assessment of suspected deep vein thrombosis)
A same-day medical assessment to find out whether a swollen, painful leg is caused by a deep vein thrombosis (a blood clot), in someone who is stable.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- If a clot may have reached the lungs — sudden breathlessness, chest pain worse on breathing in, coughing up blood, or feeling faint — call 999; do not book a private appointment.
- For a swollen, painful leg without those signs, the assessment uses a score, a blood test (D-dimer) and usually a leg ultrasound to confirm or rule out a clot.
- No single test is enough on its own: a normal D-dimer only helps when your score is low, and a scan sometimes needs repeating after about a week.
- DVT is assessed urgently on the NHS, often through same-day clot clinics; private assessment is mainly for speed or a second opinion, never for suspected clot on the lung.
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.
Safely confirms or rules out a leg clot using a recognised, evidence-based approach
Anyone with signs a clot may have reached the lungs — breathlessness, chest pain on breathing in, coughing up blood, or faintness — needs 999, not a...
Your legs are examined and scored, and you may have a D-dimer blood test and a leg ultrasound the same day. Tell staff at once if you become breathless or...
Clear written advice on the emergency signs of a clot on the lung and to call 999.
Your legs are examined and scored, and you may have a D-dimer blood test and a leg ultrasound the same day. Tell...
The score, blood test and scan results are often available together. The clinician tells you whether a clot was...
If the first scan was negative but a clot is still suspected, a repeat scan may be arranged to be sure.
If a clot is confirmed, you are given a treatment plan, advice on how long to take blood thinners, and any checks...
What is a DVT assessment?
First, the emergency point. A deep vein thrombosis (a clot in a deep leg vein) can break off and travel to the lungs, causing a pulmonary embolism, which is life-threatening. If you have sudden breathlessness, chest pain that is worse when you breathe in, you are coughing up blood, or you feel faint, clammy or panicky, call 999 now. Do not wait to book a private appointment.
A DVT assessment is for a leg that is swollen, painful, warm or discoloured, in someone who is otherwise stable and does not have the chest or breathing signs above. It works out whether a clot is the cause.
The assessment is usually done by an acute physician or a general physician, often through a dedicated same-day clot service. They take your story, examine your leg, and use a scoring tool (the Wells score) together with a blood test (D-dimer) and usually an ultrasound scan of the leg veins to confirm or rule out a clot.
Be clear about how this works. The combination of a score, a blood test and a scan is good at safely confirming or excluding a clot, but no single test does it alone. A normal D-dimer is only reassuring when your score is low, and an early scan can occasionally need repeating after about a week if suspicion remains.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
How the score and D-dimer guide the next step
| Wells score | D-dimer | Usual next step |
|---|---|---|
| DVT likely | Not relied on alone | Leg vein ultrasound, ideally within hours |
| DVT unlikely | Normal | DVT effectively excluded |
| DVT unlikely | Raised | Leg vein ultrasound to check |
| Any score | Scan negative but suspicion remains | Repeat scan after about a week may be advised |
This follows the NICE approach; your clinician applies it to your individual situation.
Preparing for your test
- First, rule out an emergency: sudden breathlessness, chest pain worse on breathing in, coughing up blood, or feeling faint means call 999 now, not book an appointment.
- If your leg is swollen or painful but you feel otherwise well, note when it started, which leg, and whether it followed a long flight, surgery, illness or immobility.
- Bring a full list of your medicines, especially any blood thinners, the contraceptive pill or HRT.
- Note your risk factors: recent surgery or hospital stay, cancer, pregnancy or recent birth, a previous clot, or a family history of clots.
- Measure or note any difference in size between your two legs if you can.
- Bring details of any previous DVT, scans or clotting problems.
- Be ready for the assessment to take a few hours if a blood test and scan are arranged on the day.
What happens
The clinician first checks you do not have signs of a clot on the lung, which would need emergency care. If you are stable, they take a history and examine both legs, comparing size, swelling, warmth and tenderness.
They then use the Wells score to estimate how likely a clot is. If a clot is judged unlikely, you usually have a D-dimer blood test; a normal result with a low score effectively rules out a DVT. If a clot is judged likely, or the D-dimer is raised, you usually have an ultrasound scan of the leg veins, ideally within hours.
The ultrasound looks directly at the deep veins for a clot. If it is negative but suspicion remains high, a repeat scan after about a week is sometimes advised, because a small clot can become easier to see.
Before you leave, you should be told whether a clot was found, what it means, any treatment (usually blood-thinning medicine if a clot is confirmed), how long results take, and what to do if you develop chest or breathing symptoms.
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…
- Anyone with signs a clot may have reached the lungs — breathlessness, chest pain on breathing in, coughing up blood, or faintness — needs 999, not a routine DVT assessment.
- Settings without same-day access to a D-dimer test and leg ultrasound, as a clot can be missed or treatment delayed.
- People for whom the test result would not change management, or where another diagnosis is clearly more likely.
- Someone expecting a single test to give a definite answer, when scoring, blood test and scan are used together.
Delay or rearrange if…
- You have any chest or breathing symptoms — this is an emergency; call 999 rather than waiting.
- The leg is severely painful, cold or pale, suggesting a more urgent problem needing immediate care.
- Key information is missing, such as a recent surgery date or current blood thinners, where it changes decisions.
- You cannot arrange same-day access to the blood test and scan the pathway needs.
Alternatives to discuss
- 999 and A&E for any suspected clot on the lung — the safest and fastest route.
- NHS same-day DVT clinic, usually arranged via your GP, NHS 111 (in England, Scotland or Wales) or A&E; in Northern Ireland, usually arranged through your GP or GP out-of-hours service.
- For advice on a swollen leg when you are unsure how urgent it is: NHS 111 in England, Scotland or Wales, or your GP out-of-hours or HSC Trust Phone First service in Northern Ireland.
- Assessment for other causes of a swollen leg (such as infection or a muscle problem) if a clot is excluded.
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
- Safely confirms or rules out a leg clot using a recognised, evidence-based approach
- Allows quick start of blood-thinning treatment if a clot is found, reducing the risk it travels to the lungs
- Avoids unnecessary treatment when a clot is excluded
- Often gives an answer the same day through a dedicated clot service
- Can prompt a look for an underlying cause and advice to reduce future clots
Risks & complications
- Mild bruising or discomfort from the blood test
- Waiting around for the blood test and scan on the same day
- A raised D-dimer that is not due to a clot, leading to a scan you may not have needed
- Anxiety while waiting for results
- A scan that is negative early on but needs repeating after about a week if suspicion remains
- An alternative cause for the leg symptoms being found that needs its own treatment
- Incidental findings that then need checking
- If a clot is confirmed, the risks of blood-thinning treatment, mainly bleeding
- A clot being missed on an early scan and only found on repeat testing
- A clot travelling to the lungs (pulmonary embolism), which is why chest or breathing symptoms must prompt 999
The main danger is a clot reaching the lungs, so any chest or breathing symptoms are an emergency. No single test is perfect: a D-dimer is only reassuring when your score is low, and an early ultrasound can occasionally miss a small clot, which is why a repeat may be advised. If a clot is confirmed, blood thinners carry a bleeding risk that must be weighed up. Ask what your score and results mean, whether you need a repeat scan, and what to watch for.
Published figures to discuss
DVT assessment relies on combining a clinical score with a D-dimer blood test and an ultrasound, because no single test is reliable alone. A D-dimer is sensitive but not specific, so it is used to rule out a clot in lower-risk people rather than to confirm one. The figures below come from NICE guidance and reflect how safe the pathway is when followed correctly; they are not a guarantee for any individual.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Clot still found within 3 months despite a reassuring assessment | Around 0.5% when DVT is judged unlikely and the D-dimer is normal | This low figure depends on the score and D-dimer being used together correctly, as set out by NICE. | NICE NG158 — Venous thromboembolic diseases: diagnosis and managementnice.org.ukPublished figure |
| Pulmonary embolism | Emergency if breathlessness, chest pain, collapse or coughing blood | DVT symptoms plus chest symptoms should be treated as possible PE, not routine leg-clot assessment. | Guide sourcesClinical context |
| D-dimer false positive | Common | Age, inflammation, cancer, pregnancy, infection and recent surgery can raise D-dimer without clot. | NHS — DVT (deep vein thrombosis)nhs.ukSource-linked context |
| Ultrasound too early or incomplete | Recognised | Repeat imaging may be needed if suspicion remains and initial scan is negative. | NHS — DVT (deep vein thrombosis)nhs.ukSource-linked 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 the assessment itself. What matters afterwards is knowing the result, starting any treatment safely, and recognising the signs that a clot may have travelled to the lungs.
- Mild bruising where blood was taken
- A leg that stays swollen or sore until the cause is treated or settles
- Waiting a few hours for the blood test and scan on the day
- Being advised to return for a repeat scan in some cases
Aftercare
- If a clot is confirmed, take blood-thinning medicine exactly as prescribed and do not stop without advice.
- Learn the signs of bleeding to watch for if you are on blood thinners, and who to contact.
- Keep any repeat scan appointment if one is advised.
- Stay active as advised, keep well hydrated, and follow guidance on flights or long periods of sitting.
- Know the emergency signs of a clot on the lung and call 999 if they occur.
- Make sure you know who to contact, and how, if your leg gets worse or new symptoms appear.
- Attend any tests for an underlying cause that your clinician arranges.
- A note of when the leg symptoms started and which leg
- Any recent surgery, flights, illness or immobility written down
- A full list of your medicines, including the pill, HRT or blood thinners
- Your risk factors noted (cancer, pregnancy, previous clot, family history)
- Any previous DVT or clotting test results
- Time set aside for a possible blood test and scan on the day
- Questions written down and a way to record your result and plan
⚠ Get urgent help if…
- Sudden breathlessness — call 999 (possible clot on the lung)
- Chest pain that is sharp or worse when you breathe in — call 999
- Coughing up blood — call 999
- Feeling faint, clammy, dizzy or panicky — call 999
- A leg that becomes severely painful, very swollen, cold or pale — seek urgent help
- If you are on blood thinners: unusual or heavy bleeding, black stools, or a significant head injury — seek urgent help
- Worsening leg swelling, redness or pain after you were sent home — seek urgent advice
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 good result is a clear answer about whether you have a leg clot, reached through a recognised combination of scoring, a blood test and a scan. If a clot is confirmed, treatment can start quickly; if it is excluded, you avoid unnecessary blood thinners and can be pointed towards the real cause of your leg symptoms.
The limits are built into how the tests work. A normal D-dimer only helps when your score is low. An early ultrasound can occasionally miss a small clot, which is why a repeat scan is sometimes advised. A normal assessment today does not prevent a future clot, so new symptoms still need attention.
The result applies to this episode. If you develop new leg swelling or pain in future, or any signs of a clot on the lung, you need assessing again — an earlier normal result does not protect you. If you have ongoing risk factors, such as cancer or a previous clot, your risk remains higher and may need long-term management.
Related tests, treatments or support
A DVT work-up combines the Wells score with a D-dimer blood test and a leg vein ultrasound, used together rather than alone. If a clot is confirmed, your clinician may look for an underlying cause and assess your bleeding risk before choosing treatment. If breathing or chest symptoms appear, assessment for a clot on the lung (often a CT scan of the lung arteries) takes priority.
Follow-up & long-term care
How you get your results depends on the setting, but a same-day clot service often gives an answer the same day. You should leave knowing the result, any treatment and how long to take it, whether a repeat scan is needed, who will act on outstanding results, and exactly what to do if chest or breathing symptoms develop.
- If on blood thinners, take them as prescribed and attend any monitoring or reviews.
- Discuss how long treatment should last and when it will be reviewed.
- Reduce future risk where you can: stay active, keep hydrated, and move on long journeys.
- Tell future clinicians you have had a DVT, as it affects later decisions.
Repeat, follow-on and what comes next
- A negative early ultrasound with continued suspicion may need a repeat scan after about a week.
- A raised D-dimer is common and non-specific, so it often leads to a scan rather than confirming a clot.
- If symptoms change or chest or breathing signs appear, assessment is repeated and a clot on the lung is considered urgently.
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 written advice on the emergency signs of a clot on the lung and to call 999.
- If treated, a plan for how long to take blood thinners, bleeding precautions and a review date.
- A named contact for results, a repeat scan if needed, and any underlying-cause checks.
- Honest explanation of what the result does and does not rule out.
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:
- How urgently you are seen and whether the assessment is in a same-day clot clinic
- Which clinician assesses you (acute physician or general physician)
- The D-dimer blood test and any other blood tests
- The leg vein ultrasound scan, and whether a repeat scan is needed
- Whether a specialist reports the scan on the same day
- Any blood-thinning treatment if a clot is confirmed, and follow-up
- The clinician's assessment fee and which specialty they are from
- The cost of the D-dimer and any other blood tests
- The cost of the leg vein ultrasound, and a repeat scan if needed
- Whether scan reporting is included
- What happens, and what it costs, if a clot is confirmed and treatment is needed
- Any follow-up appointment and how results are communicated
- The cancellation policy and what happens if you develop chest or breathing symptoms
On the NHS? Suspected DVT is assessed urgently on the NHS, often through same-day clot clinics, and suspected clot on the lung through 999 and A&E; private same-day assessment is mainly used for speed, choice or a second opinion in stable patients, never as a substitute for emergency care.
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
- A normal D-dimer being treated as reassuring even when the clinical score is high.
- No clear advice on the emergency signs of a clot on the lung.
- If a clot is confirmed, blood-thinner bleeding risks not being clearly explained.
- Being steered into a private booking when chest or breathing symptoms actually need emergency care.
- No plan for a repeat scan when the first is negative but suspicion remains.
Marketing red flags
- Any service that assesses possible clot on the lung instead of telling you to call 999.
- Offering a D-dimer alone as a way to 'rule out a clot' without scoring or a scan.
- Claims that one scan gives a lifelong all-clear for clots.
- Same-day private appointments promoted as a substitute for emergency care.
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.
- What is my Wells score, and what does it mean for which tests I need?
- Does my D-dimer and scan result confirm or rule out a clot, and how sure are you?
- Do I need a repeat scan, and if so, when?
- If I have a clot, what treatment do I need, for how long, and what are the bleeding risks?
- Exactly what should I do if I become breathless or get chest pain?
- Should I be checked for an underlying cause of the clot?
- 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
When is a leg clot an emergency rather than something to book about?
Why do I need a score, a blood test and a scan?
My D-dimer was raised — does that mean I have a clot?
Why might I need a second scan a week later?
Is a DVT assessment available on the NHS?
What happens if a clot is confirmed?
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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: NHS — DVT (deep vein thrombosis) NHS — Pulmonary embolism NICE NG158 — Venous thromboembolic diseases: diagnosis and management RCEMLearning — Deep Vein Thrombosis Society for Acute Medicine — Same Day Emergency Care nidirect — urgent and emergency care (Northern Ireland) nidirect — GP out-of-hours service (Northern Ireland)
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.
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