D-dimer test
Informed by recognized medical guidance
Overview
A D-dimer test is a blood test that helps doctors check for blood clotting problems. It measures a substance called D-dimer, which is released when a blood clot breaks down. A normal result makes it very unlikely that you have a dangerous blood clot, but a high result can happen for many reasons and does not mean you definitely have a clot.
Key facts
- The test is used to help rule out deep vein thrombosis (DVT) and pulmonary embolism (PE).
- A negative result is very reliable for ruling out clots in people with low risk.
- A positive result does not confirm a clot; further tests like an ultrasound or CT scan are usually needed.
D-dimer tests are common in hospitals and clinics, especially in emergency departments when someone has symptoms that could be from a blood clot.
It is used for people of any age who have symptoms that could be from a blood clot. Doctors may order it for people with leg pain or swelling, or sudden shortness of breath.
Symptoms
- Sudden severe shortness of breath
- Chest pain that does not go away
- Coughing up blood
- Fainting or feeling like you might pass out
- ⚠Swelling or pain in one leg that gets worse
- ⚠Redness or warmth in the leg that does not improve
- ⚠Unexplained shortness of breath that is mild but persistent
Common symptoms
- Swelling in one leg (calf or thigh)
- Pain or tenderness in the leg, especially when standing or walking
- Skin on the leg feeling warm to the touch
- Sudden shortness of breath
- Chest pain that gets worse with deep breathing or coughing
- Coughing up blood
Symptoms in children
- Children rarely develop blood clots, but if they do, symptoms are similar to adults: leg swelling, pain, or sudden breathing trouble.
Symptoms in older adults
- In older adults, symptoms may be less obvious, such as unexplained shortness of breath or mild leg discomfort.
Causes
Main causes
- Blood clot in a deep vein (DVT) or a clot that has traveled to the lungs (PE)
- Recent surgery or major injury
- Pregnancy or recent childbirth
- Infection or inflammation
- Cancer
Risk factors
- Being over age 60
- Prolonged sitting (e.g., long flights or car rides)
- Being overweight or obese
- Smoking
- Taking birth control pills or hormone replacement therapy
- Having a family history of blood clots
- Having had a clot before
- Certain medical conditions like heart disease or cancer
When to see a doctor
See a doctor urgently if:
- If you have sudden shortness of breath or chest pain, call your local emergency number immediately.
- If you have leg swelling or pain that comes on suddenly and is severe, see a doctor the same day.
Book a routine appointment if:
- If you have mild leg swelling or discomfort that does not go away, make an appointment with your doctor.
- If you are at high risk for clots (e.g., after surgery), talk to your doctor about whether you need monitoring.
Diagnosis
A D-dimer test is done by taking a small sample of blood from a vein in your arm. The sample is sent to a lab to measure the level of D-dimer.
Tests that may be done
- D-dimer blood test
- Ultrasound of the leg (if DVT is suspected)
- CT scan of the chest (if PE is suspected)
- Blood tests to check for other causes
What to expect at your appointment
The blood test is quick and feels like a standard blood draw. Results are usually available within a few hours. If the result is high, your doctor may order imaging tests to look for a clot. You may need to wait a little longer for these results.
Treatment
If a blood clot is found, treatment aims to stop the clot from growing and prevent it from breaking loose and traveling to the lungs. Treatment usually involves blood-thinning medicines.
Self-care at home
- Stay as active as possible, but avoid strenuous activity if you have a clot.
- Wear compression stockings if your doctor recommends them to reduce leg swelling.
- Drink plenty of fluids and move around regularly, especially on long trips.
Medical treatments
Blood-thinning medicines (anticoagulants) are the main treatment. They are usually taken as pills or given as injections. Treatment typically lasts at least three to six months. Your doctor will monitor you with blood tests to make sure the dose is right. Never stop or change your medicine without talking to your doctor.
When is surgery considered?
In rare cases, if a clot is very large or if blood thinners cannot be used, surgery may be needed to remove the clot. This is not common.
Living with this condition
If you have had a blood clot, you will likely need to take blood thinners for several months. You may need regular blood tests. Be careful to avoid injuries that could cause bleeding, and let all your healthcare providers know you are on blood thinners.
Lifestyle tips
- Avoid sitting for long periods without moving. Get up and walk every hour on long flights or drives.
- Quit smoking – smoking increases your risk of clots.
- Maintain a healthy weight to reduce strain on your veins.
- Wear loose-fitting clothing and avoid tight socks or stockings unless prescribed.
Diet and exercise
Eat a balanced diet with plenty of fruits, vegetables, and whole grains. If you are on a blood thinner called warfarin, you may need to keep your vitamin K intake consistent (your doctor will advise). Regular gentle exercise like walking is good for circulation, but avoid contact sports that could cause injury.
Mental health and emotional wellbeing
Worrying about having another clot is natural. Talk to your doctor about your concerns. Some people find it helpful to join a support group or speak with a counselor.
Prevention
Many blood clots can be prevented. Staying active, not smoking, and managing conditions like obesity and heart disease help. After surgery, your doctor may give you blood thinners or compression devices to prevent clots.
Screening programmes
Screening for blood clots is not routine for most people. If you have a high risk (e.g., family history), your doctor may recommend taking preventive measures during long trips or before surgery.
Complications
If left untreated
- A blood clot in the leg can travel to the lungs, causing a pulmonary embolism, which is life-threatening.
- A clot that is not treated can cause permanent damage to the veins in the leg, leading to chronic pain, swelling, and skin changes (post-thrombotic syndrome).
Long-term outlook
With prompt treatment, most people recover fully from a blood clot. Taking blood thinners as prescribed greatly reduces the risk of another clot. Your doctor will work with you to manage your risk factors and keep you healthy.
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Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
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Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 16, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.
Guidance may differ by country or region. Confirm local recommendations with a qualified healthcare provider.