Patients often ask me “but I’m healthy — why did I get a blood clot?” The honest answer is that DVT rarely has a single cause. It’s usually a combination of factors that tip the balance towards clotting, and understanding your own combination is the first step to preventing a recurrence.
🧬 The Three Mechanisms (Virchow’s Triad)
- Slowed blood flow (stasis) — long-haul flights, bed rest, immobility after surgery or illness
- Vein wall damage — surgery, trauma, previous DVT, IV catheters
- Increased clotting tendency — cancer, pregnancy, oestrogen-containing medication, inherited clotting disorders, dehydration
⚠️ Common Risk Factors in Everyday Life
- Recent major surgery — especially hip, knee, or abdominal/pelvic operations
- Long-haul flights or car journeys over 4 hours
- Active cancer or cancer treatment
- Pregnancy and the first 6 weeks postpartum
- Oral contraceptives or hormone replacement therapy
- Obesity and a sedentary lifestyle
- Smoking
- Age over 60
- A family history of blood clots
🧪 When to Test for Inherited Clotting Disorders
Most DVTs have an obvious trigger (surgery, travel, immobility) and don’t need clotting-disorder testing. I generally consider it when a patient has DVT at a young age (under 45–50) with no clear trigger, recurrent clots, or a strong family history. Conditions like Factor V Leiden or Protein C/S deficiency are uncommon but change how long anticoagulation is needed.
💬 My Clinical Perspective
Many patients feel they did something wrong to “cause” their clot. In reality, most DVTs happen because two or three ordinary risk factors line up at once — a long flight while dehydrated, for instance, in someone recovering from minor surgery. Identifying your personal risk factors matters most for prevention next time, not for assigning blame this time.
❓ Frequently Asked Questions
Can DVT happen without any risk factors?
Occasionally, yes — these are called ‘unprovoked’ DVTs. They are taken more seriously because they may point to an underlying clotting disorder or, in older patients, an undiagnosed cancer, so further investigation is sometimes recommended.
Does dehydration cause DVT?
Dehydration thickens the blood slightly and can contribute to clot formation, particularly when combined with immobility such as a long flight. It’s rarely the sole cause but is a modifiable risk factor worth addressing.
Is DVT hereditary?
It can run in families, particularly when an inherited clotting disorder is present. If you have a first-degree relative with DVT at a young age or without a clear trigger, mention this to your doctor.
📖 Related Reading:
- What Is DVT? A Patient’s Guide — and Why Treatment Matters
- Signs and Symptoms of DVT
- Deep Vein Thrombosis (DVT) & Pulmonary Embolism — Diagnosis to Treatment
Concerned about your personal DVT risk? I offer vascular consultations at CARE Hospitals, Banjara Hills, Hyderabad.
Dr Rahul Agarwal is a Consultant Vascular & Endovascular Surgeon at CARE Hospitals, Banjara Hills, Hyderabad (MBBS, DNB, DrNB).
Medical Disclaimer: This article is for educational purposes only and does not constitute medical advice. Please consult a qualified medical professional for diagnosis and treatment.