Most often, passing small blood clots during your period isn't a cause for concern. The amount, length and frequency of menstrual bleeding vary from month to month and from person to person.

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.

Your doctor or care team member can find out if a medical problem is the cause. You might need a blood test to check for anemia, a condition that can cause you to feel weak or tired. You also might need other exams, such as an ultrasound of the pelvis.

Sometimes, hormonal medicines are used to control heavy menstrual bleeding. Certain other medicines also may help.