## Why it’s dangerous Blood clots, or thrombi, are clumps of blood that form when platelets stick together. They can form in both veins and arteries. Sometimes clots result from abnormalities in the blood’s clotting system; other times, they form in response to damage in a blood vessel’s inner lining. Once attached to the vessel wall, a clot may remain stable, but under certain conditions, it can break off. If this happens, the clot can travel through the bloodstream and block a narrower vessel, potentially leading to a heart attack, ischemic stroke, or other serious health complications. ## Who is at risk? - People over age 50 - Pregnant women - Those taking hormonal medications - Individuals recovering from COVID-19 - People with varicose veins, obesity, or cancer > One key lab marker used by doctors to assess clotting risk is D-dimer — a protein fragment released into the blood when a clot breaks down. Elevated D-dimer levels may indicate a tendency to form clots, even if no symptoms are present. ## What you can do - Consult your doctor before flying, especially if you’ve had clots before or have a high D-dimer level. - Wear compression stockings, as they help improve circulation in your legs. - Stay hydrated. Dehydration makes your blood thicker. - Avoid alcohol, as it can contribute to dehydration. - Skip sleeping pills. They lead to deep sleep, increasing the amount of time you stay motionless, which raises the risk of blood stagnation. - Move regularly. Get up and stretch every 1–2 hours. Even small circular movements of your feet while sitting can help keep blood flowing.