Blood Clots, Stroke & VTE

This page is general information for people in the UK. It is not a diagnosis and it is not a substitute for advice from your GP, pharmacist, anticoagulation clinic or hospital team. If you think you or someone else may have a clot, do not wait to finish reading — get medical help straight away.^{[3]NHS — blood clots}

Blood is meant to clot — it is how bleeding stops when you are injured. A problem arises when a clot forms inside a blood vessel where it is not needed, blocks the flow of blood, or breaks away and travels somewhere else in the body.^[3]NHS

• Deep vein thrombosis (DVT) — a clot in a deep vein, most often in the lower leg or thigh, sometimes in the pelvis or an arm. It can damage the vein and can be the source of a clot that travels to the lungs.^{[1]NHS — DVT}
• Pulmonary embolism (PE) — part of a clot breaks off, travels through the bloodstream and blocks an artery in the lungs. This is an emergency.^{[2]NHS — pulmonary embolism}
• Venous thromboembolism (VTE) — the umbrella term used by the NHS and NICE for DVT and PE together. You may see it on hospital paperwork and risk assessments.^{[11]NICE NG158}
• Arterial clots — clots forming in arteries can cause a stroke or a heart attack. These are treated as separate emergencies with their own care pathways.^{[4]NHS — stroke}
• Clots linked to an irregular heartbeat — atrial fibrillation (AF) can allow clots to form in the heart, which raises the risk of stroke. Treatment usually includes assessing whether an anticoagulant is needed.^{[6]NHS — atrial fibrillation[14]NICE NG196}
• Superficial thrombophlebitis — a clot with inflammation in a vein just under the skin. It is usually less serious than a DVT, but it should still be assessed, because it can sometimes extend into a deep vein.^[3]NHS

DVT symptoms usually affect one leg (or, less often, one arm) rather than both, and they often build up over hours or days rather than instantly. Look for:^{[1]NHS — DVT}

• throbbing, cramping or aching pain, often in the calf or thigh
• swelling in the leg, ankle or foot on one side
• skin that feels warm to the touch around the painful area
• a change in skin colour — the skin may look red, darker, or purplish, and colour changes can be harder to see on brown and black skin, so pay attention to swelling, warmth and pain as well
• swollen veins that feel hard or sore when you touch them

Some people have very mild symptoms, and a few have none at all until a clot causes problems elsewhere. If a leg suddenly becomes painful and swollen, please get it checked the same day rather than waiting to see whether it settles.

Several things can increase risk, and often more than one applies at the same time. Having a risk factor does not mean you will get a clot, and some people develop a clot with no obvious cause at all — that is called an unprovoked clot, and it is not anyone’s fault.^{[1]NHS[11]NICE NG158}

• recent surgery, especially hip, knee, pelvic or cancer surgery
• a stay in hospital, or a serious illness or injury that keeps you in bed
• being immobile for long periods, including after a fracture or while wearing a cast
• long journeys, generally described as travel of four hours or more without moving about
• pregnancy, and the weeks after giving birth
• cancer, and some cancer treatments
• a previous DVT or pulmonary embolism
• a close family history of clots, or an inherited clotting condition (thrombophilia)
• combined hormonal contraception, and some hormone replacement therapy
• smoking
• living with obesity
• getting older
• dehydration, and some long-term conditions such as inflammatory bowel disease or heart failure

If you are worried about your own risk — particularly before surgery, a long flight, or when starting a hormonal medicine — ask your GP, pharmacist or the team looking after you. They can look at your full history, which we cannot do.

You cannot diagnose a clot at home, and no app or wearable can rule one out. Assessment usually starts with your history and an examination, then tests chosen by the clinician.^{[11]NICE NG158}

Most clots are treated with anticoagulant medicines, often called blood thinners. They do not dissolve the clot directly; they stop it growing and reduce the chance of a new one forming while your body breaks the clot down.^{[7]NHS — anticoagulants}

Contact your GP, anticoagulation clinic, pharmacist or NHS 111 the same day if you notice unusual bruising, nosebleeds that keep coming back, bleeding gums, heavier periods than normal, or blood anywhere you would not expect it, without the emergency signs above.^{[16]NHS 111}

You can report a suspected side effect from any medicine through the MHRA Yellow Card scheme. This does not replace getting medical help.^{[15]MHRA Yellow Card}

Pregnancy and the weeks after birth raise the risk of clots, and hormonal medicines can also affect risk. These situations need personal advice from a clinician who knows your history.^{[1]NHS — DVT}

• In pregnancy or after birth — contact your midwife, maternity unit or GP urgently if you have leg pain or swelling, and call 999 for breathlessness, chest pain, coughing up blood or collapse. Some anticoagulants are not suitable in pregnancy, so treatment is chosen by a specialist.
• Contraception — if you have had a clot or have a known clotting condition, discuss contraception with your GP or a sexual health clinic. Do not stop a prescribed contraceptive without advice, and do not assume a method is safe or unsafe based on general information.
• Hormone replacement therapy — different types of HRT carry different risks. If you are considering HRT, or already take it and have had a clot, ask your GP or menopause clinician to review it with you.

We do not give personal advice on starting or stopping hormonal medicines. Please ask a clinician who can see your full record.

Many people recover well after a clot, but recovery can take time. Breathlessness on exertion after a PE, or leg swelling and aching after a DVT, can last for months. Some people develop longer-term leg symptoms known as post-thrombotic syndrome.^{[11]NICE NG158}

• Go to your follow-up appointments, and ask who to contact between them.
• Ask what your plan is for how long treatment continues and when it will be reviewed.
• Build activity back up gradually, following the advice of your team.
• Ask about compression stockings if you have ongoing leg swelling — they should be assessed and fitted properly.
• Learn your personal warning signs, and act on them early rather than waiting.
• Tell any new healthcare professional that you have had a clot — it stays relevant for years.

A clot is frightening, and it is common to feel anxious afterwards, to worry about every twinge, or to have low mood or trouble sleeping. That reaction is understandable and you are not being dramatic.

• Tell your GP if worry, low mood or sleep problems are affecting your daily life.
• NHS talking therapies can be accessed through your GP, and in England you can usually self-refer.
• Thrombosis UK is a national charity, not an NHS service, offering patient information and support after a clot.^{[17]Thrombosis UK}
• Anticoagulation UK supports people taking blood-thinning medicines.^{[19]Anticoagulation UK}
• The Stroke Association supports stroke survivors and their families — please check current helpline numbers and opening hours on its website.^{[18]Stroke Association}

In a life-threatening emergency, always call 999.