Platelets can also repair damaged blood vessel walls. If the walls of your veins are uneven, for example because of too much cholesterol, the platelets may break against them and cause a blood clot to form. A blood clot that blocks blood flow near the heart or the brain can have fatal consequences.

Blood clots form in stages when cholesterol is accumulated in the artery walls. As the arterial diameter decreases, the blood pressure in the vessel rises. The blood clot forms when platelets accumulate in the narrow space. Eventually, the artery becomes blocked.