This is called excessive blood clotting or hypercoagulation and can be very dangerous. In a case of excessive blood clotting, these clots can form in, or travel to, the arteries or veins of any organ, which can cause heart attack, stroke, damage to the body’s organs or even death.

But if you pass large blood clots that are bigger than a grape, seek medical care. Large blood clots can be part of a heavy period, which may be a sign of a serious medical issue. When a period is heavier than usual, it also might cause you to soak through one pad or tampon every hour for many hours in a row.

Thrombosis is a serious condition where one or more blood clots form in your blood vessels or heart. When this happens, the clot can block blood flow where it formed, or it can break loose and travel elsewhere in your body. If a moving clot gets stuck in a critical area, it can cause life-threatening conditions like stroke and heart attack.

Clotting that occurs in arteries is usually associated with atherosclerosis (hardening of the arteries), a deposit of plaque that narrows the inside of the vessel. As the arterial passage narrows, the strong arterial muscles continue to force blood through the opening, and the high pressure can cause the plaque to rupture.