A deep vein thrombosis (DVT) is a blood clot in a deep vein, usually in the calf or thigh. It typically causes swelling, pain, warmth and redness in one leg, and it can look very like a calf strain. It needs medical assessment the same day, because part of the clot can travel to the lungs and cause a pulmonary embolism. It is treated with anticoagulant medicine, not with exercise or hands-on treatment.
Also known as DVT, blood clot in the leg, venous thromboembolism
Anatomy: where the problem is
Side view of the lower leg. Highlighted in the diagram: deep veins of the calf.
Symptoms
- Throbbing pain or tenderness in one leg, usually the calf or thigh, when walking or standing
- Swelling in one leg
- Warm skin over the painful area
- Red or darkened skin, which may be harder to see on brown or black skin
- Swollen veins that are hard or sore to touch
- Sometimes few or no symptoms
Causes and risk factors
- A recent operation or hospital stay
- Being immobile for a long time, such as a leg in a cast or a long journey
- Pregnancy and the six weeks after birth
- Cancer and some cancer treatments
- The combined contraceptive pill or HRT
- A previous DVT, being over 60, being overweight or smoking
What the evidence says helps
- If a DVT is suspected, NICE recommends a clinical risk score, a blood test called a D-dimer where appropriate, and an ultrasound scan of the leg veins, ideally within four hours.1
- If the scan cannot be done within four hours, an anticoagulant medicine is started in the meantime.1
- A confirmed DVT is treated with anticoagulant tablets, usually for at least three months.1
- Using a risk score together with a D-dimer test safely rules out DVT in many people without the need for a scan.3
- NICE advises against using compression stockings to prevent long-term leg problems after a DVT.1
Things you can try at home
- Do not wait: call your GP or NHS 111 the same day if you think you might have a DVT
- Do not massage a calf that is swollen, warm and painful
- To lower your risk, stay active and avoid long periods of sitting still
- On long journeys, walk about regularly, drink water and do calf exercises in your seat
- After surgery or with a leg in a cast, follow the advice you are given about blood-thinning injections or tablets
- If you have had a clot before, tell clinicians before any surgery or long period of immobility
When to get urgent help
Contact your GP urgently, call NHS 111, or call 999 in an emergency if you have:
- Throbbing pain, swelling, warmth or redness in one leg: ask for an urgent GP appointment or call NHS 111 the same day
- Leg pain and swelling together with breathlessness or chest pain: call 999
- Sudden breathlessness, sharp chest pain that is worse on breathing in, or coughing up blood: call 999
- Symptoms of DVT during pregnancy or in the six weeks after birth: contact your midwife, GP or NHS 111 the same day
How Apollo can help
We do not treat DVT, and our job is to make sure it is not missed. Calf strains and blood clots can look alike, so with any calf pain we ask about risk factors and check for swelling, warmth and tenderness. If there is any suspicion of a clot, we do not treat the leg: we arrange same-day medical assessment and give you a letter with our findings. Once a clot has been treated and your doctor is happy, we can help you return to activity gradually.
No GP referral needed. Clinics in Sheringham, Coltishall and Norwich.
Related reading
Frequently asked questions
How can I tell a DVT from a pulled calf muscle?
You often cannot, which is why it needs checking. A strain usually starts with a specific movement and hurts when the muscle is stretched or used. A DVT is more likely to cause swelling of the whole lower leg, warmth and a change in skin colour, sometimes with no injury at all. If in doubt, get same-day medical advice.
Is a DVT an emergency?
It needs medical assessment the same day. If you also have breathlessness or chest pain, call 999, because a clot may have travelled to the lungs.
Can I exercise after a DVT?
Yes, once treatment has started and your doctor agrees. Walking is encouraged and does not make the clot more likely to move. Build up gradually and report any new swelling, pain or breathlessness.
References
- National Institute for Health and Care Excellence (2020). Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. NICE guideline NG158. View source
- NHS. DVT (deep vein thrombosis). NHS website, accessed November 2026. View source
- Wells PS, et al. (2003). Evaluation of D-Dimer in the Diagnosis of Suspected Deep-Vein Thrombosis. New England Journal of Medicine 349:1227-1235. View source
This page is general information, not a diagnosis or a substitute for medical advice. If you are worried about your symptoms, speak to your GP or a registered healthcare professional. Content prepared from the sources above, November 2026.
