A long flight home, a week in bed after surgery, or simply ten hours a day at a desk — these everyday situations share a hidden danger: a blood clot forming silently in the deep veins of the leg. Known as deep vein thrombosis (DVT), it can cause a swollen, painful calf, but its real threat is what happens when a piece of that clot breaks off and travels to the lungs, causing a potentially fatal pulmonary embolism (PE). Long assumed to be rare in Indians, venous clots are now recognised as a genuine and rising problem, with DVT estimated to affect about 1% of Indian adults over 40 each year and far more among hospitalised patients.
This guide explains how DVT and PE develop, who is at risk, the warning signs you must never ignore, and how these clots are diagnosed and treated in India.
What Are DVT and Pulmonary Embolism?
Your body has a clotting system designed to stop bleeding when you are injured. Sometimes, though, a clot forms inside a vein when it shouldn't — usually in the deep veins of the calf or thigh. This is deep vein thrombosis.
A DVT becomes dangerous when part of the clot dislodges, travels up through the heart, and lodges in the arteries of the lungs. This blockage is a pulmonary embolism, and it can suddenly cut off blood flow to part of the lung. Together, DVT and PE are referred to as venous thromboembolism (VTE).
PE is a medical emergency. Indian tertiary-care data suggest that among patients who develop PE, it can be a major contributor to death, which is why recognising DVT early — before it reaches the lungs — saves lives.
Why Do Clots Form? The Three Classic Triggers
Over 150 years ago, the physician Rudolf Virchow described three conditions that promote clotting, and they remain the framework doctors use today (Virchow's triad):
- Stagnant blood flow (stasis): Long periods of immobility — bed rest after surgery, long-haul flights, prolonged desk work, or a leg in a plaster cast — let blood pool in the leg veins.
- Injury to the vein wall: Surgery, trauma, fractures, or intravenous lines can damage the vein lining and invite a clot.
- Blood that clots too easily (hypercoagulability): Pregnancy, cancer, certain medications, dehydration, and inherited clotting disorders all tip the balance toward clotting.
When two or more of these factors combine — say, surgery (injury + immobility) in someone with cancer — the risk multiplies.
Who Is at Risk in India?
Indian studies have identified a familiar set of risk factors. You are at higher risk if you have:
- Recent major surgery, especially orthopaedic procedures like hip or knee replacement
- Prolonged immobility — hospital admission, long flights or train journeys, or a sedentary IT-sector lifestyle
- Cancer and chemotherapy
- Pregnancy and the weeks after delivery
- Use of oestrogen-containing oral contraceptive pills or hormone therapy
- Obesity, smoking, and increasing age
- Co-existing conditions such as diabetes, hypertension, and COPD
- A previous DVT or a family history of clots
- Tuberculosis, which some Indian studies have flagged as an under-appreciated risk factor for PE
The sedentary nature of modern Indian office and IT work, combined with rising rates of obesity and diabetes, means VTE is no longer something that only happens "to others."
Warning Signs You Must Never Ignore
Symptoms of DVT (usually in one leg)
- Swelling of one calf or the whole leg
- Pain or tenderness, often starting in the calf, that may feel like a cramp
- Warmth over the affected area
- Redness or a bluish discolouration of the skin
- The leg feeling heavy
DVT almost always affects one leg, not both — swelling in both legs is more often due to other causes.
Symptoms of Pulmonary Embolism — A Medical Emergency
If a clot reaches the lungs, the signs can come on suddenly:
- Sudden breathlessness, even at rest
- Sharp chest pain that worsens when you breathe deeply
- Rapid heartbeat
- Coughing, sometimes with blood-streaked sputum
- Light-headedness, fainting, or a feeling of impending doom
Sudden breathlessness or chest pain demands emergency care — call for an ambulance or get to a hospital immediately. Do not wait to see if it passes. Some of these symptoms overlap with a heart attack, and both are emergencies.
How DVT and PE Are Diagnosed
Doctors combine your symptoms, a risk score, and tests:
D-Dimer Blood Test
D-dimer is a protein fragment released when a clot breaks down. The test is highly sensitive but not very specific — meaning a negative D-dimer in a low-risk patient very reliably rules out a clot, but a positive result can occur for many reasons (infection, pregnancy, recent surgery) and needs imaging to confirm. It is best thought of as a "rule-out" test.
Doppler Ultrasound
A compression Doppler ultrasound of the leg is the main test for diagnosing DVT. It is painless, widely available across Indian cities, and shows whether blood is flowing normally through the deep veins.
CT Pulmonary Angiography (CTPA)
When PE is suspected, a CT pulmonary angiogram — a special CT scan of the lung arteries with contrast dye — is the gold-standard test to visualise a clot in the lungs.
Typical Reference Range
| Test | Result interpretation |
|---|---|
| D-dimer | < 0.5 mg/L (or < 500 ng/mL) is generally negative |
| D-dimer | Raised values need ultrasound or CT to confirm a clot |
Note: Units and cut-offs vary between labs such as SRL, Thyrocare, and Dr. Lal PathLabs, and the threshold rises with age. Always have your physician interpret D-dimer alongside your symptoms — never in isolation.
Treatment: Anticoagulation and Beyond
The cornerstone of treatment is anticoagulation — "blood-thinning" medication that stops the clot from growing and prevents new clots while your body slowly dissolves the existing one.
- Direct oral anticoagulants (DOACs) such as rivaroxaban (Xarelto) and apixaban (Eliquis) are now first-line for many patients in India because they are convenient and carry a lower bleeding risk than older drugs. They require no routine blood monitoring.
- Warfarin (Acitrom, Warf) is still used, especially where DOACs are unaffordable or contraindicated, but it needs regular PT/INR blood tests to keep the dose safe.
- Low-molecular-weight heparin injections (enoxaparin) are often used in hospital, in pregnancy, and in cancer-associated clots.
- Treatment usually continues for at least 3 months; some people need it longer or lifelong depending on the cause.
- For a large, life-threatening PE, doctors may use clot-busting (thrombolytic) drugs or, rarely, a procedure to remove the clot.
Because anticoagulants increase bleeding risk, never start, stop, or change the dose without your doctor's guidance, and report any unusual bleeding promptly. If you are on warfarin, keeping your INR results organised over time matters — you can track these values with MedicalVault's trend analysis and bring a clear history to every appointment.
Preventing Clots: Simple, Effective Steps
Much of VTE is preventable. Practical measures include:
- Move regularly. On long flights or train journeys, stand, walk the aisle, and flex your calf muscles every hour. At your desk, take movement breaks.
- Stay hydrated, especially when travelling or in hot weather.
- Wear graduated compression stockings if your doctor recommends them after surgery or for high-risk travel.
- Follow post-surgery instructions, including early mobilisation and any prescribed preventive blood thinners — hospitals routinely assess this risk for major surgery.
- Manage weight, stop smoking, and discuss the clot risk of contraceptive pills with your gynaecologist if you have other risk factors.
Key Takeaways
- DVT is a blood clot in a deep leg vein; if it breaks off and reaches the lungs it causes a pulmonary embolism, a life-threatening emergency.
- Clots are no longer considered rare in Indians — immobility, surgery, obesity, pregnancy, and a sedentary lifestyle all raise the risk.
- One-sided leg swelling, pain, and warmth are the classic DVT warning signs; sudden breathlessness or chest pain means call for emergency help immediately.
- Diagnosis uses the D-dimer test, Doppler ultrasound, and CT pulmonary angiography.
- Treatment is anticoagulation — DOACs like rivaroxaban and apixaban, warfarin, or heparin — usually for at least three months.
- Prevention is powerful: move often, stay hydrated, use compression stockings when advised, and follow post-surgery guidance.
- Keep your D-dimer, INR, and scan reports in one place with MedicalVault so you and your family can share them securely across doctors.
This article is for education only and is not a substitute for professional medical care. If you suspect a blood clot, seek medical attention without delay.