Blood clots may not be the most pleasant topic to dwell on, but here’s the hard truth: they’re a quiet danger that affects hundreds of thousands of people each year, often with little to no warning. While they aren’t always fatal, ignoring them can lead to severe and lasting health problems. That’s why when cardiologists raise a serious alarm and say, “Stop doing this immediately,” it’s wise to pay attention.

So what’s the habit they’re talking about?

Sitting for extended periods of time.
Yes—something as ordinary as spending hours on the couch, staying glued to your laptop, or remaining seated throughout a long flight without moving can significantly increase the risk of dangerous blood clots.

Let’s take a closer look at what’s happening inside your body—and how you can keep your circulation healthy.

What Are Blood Clots, Really?

Think of blood clots as your body’s built-in repair system. When you scrape your knee or cut a finger, platelets rush in and clump together to stop the bleeding. That process creates a clot—and in those situations, it’s essential.

Trouble begins when clots form inside blood vessels without a clear reason. Picture traffic on a busy highway suddenly coming to a complete stop for no apparent cause—that’s similar to what happens when a clot disrupts the normal flow of blood through your veins or arteries. If a clot breaks loose and travels, it can become lodged in the lungs (causing a pulmonary embolism), the brain (leading to a stroke), or the heart (triggering a heart attack), resulting in potentially life-threatening consequences.

So Why Is Sitting Such a Big Deal?

It turns out that sitting for long stretches—whether during a 12-hour Netflix binge, a cross-country flight, or a regular day at a desk job—can cause blood to pool, especially in the lower legs. As blood isn’t moving, it becomes more likely to clot.

As per Dr. Danielle Belardo, a preventive cardiologist, regular movement encourages healthy blood circulation. “Your muscles help push blood through your veins. When they aren’t being used, blood flow slows down—and that’s where the danger begins,” she explains.

Dr. Mohanakrishnan Sathyamoorthy, another leading cardiologist, backs this up. He says that the condition known as venous stasis—where blood stays still in one spot too long—is among the key ingredients in the recipe for clot formation.

And here’s the kicker: you don’t have to be old or already sick to be at risk. Even healthy young adults can experience clotting problems, especially if their lifestyle includes long periods of immobility.

What Else Causes Blood Clots?

Though prolonged sitting is a big trigger, it’s not the only one. Below are some other major culprits:

1. Medical Conditions

Some conditions increase the likelihood of clotting. These include:

Can:cer and chemotherapy
Heart disease
Autoimmune disorders
Genetic clotting disorders (like Factor V Leiden)

2. Injuries or Surgeries

Major surgeries, especially involving the hips, legs, or abdomen, raise clotting risks. Why? Because recovery often involves long periods of bed rest—aka zero movement.

3. Hormonal Shifts

Women that are pregnant, on birth control pills, or undergoing hormone replacement therapy may be at higher risk because of changes in estrogen levels, which can make blood more prone to clot.