Passing blood clots during menstrual cycles is often a normal occurrence during the heaviest days of the period. However, heavy bleeding and passing large clots can sometimes be a cause for concern. Here are some potential causes for large blood clots during periods:

• Uterine obstruction like a fibroid
• Thyroid conditions
• Over-the-counter and prescribed medications
• Medical conditions that cause large blood clots, often alongside heavy menstrual bleeding or period pains
• Uterine fibroids
• Heavy menstrual bleeding (menorrhagia)

If the clots are larger than a quarter in size, very frequent, or occur with an abnormally heavy flow that requires a person to change their tampon or pad after less than 2 hours, it is advisable to seek medical advice. A doctor can determine if theres an underlying problem causing heavy periods and recommend appropriate treatment.