What are clots in period blood?
Last updated September 3, 2026.
Clots are coagulated blood and tissue - usually a flow-rate story: anticoagulants that keep menstrual blood moving get outpaced on heavy days, so blood gels on the way out, worst on heavy days and first thing in the morning. Small dark clots on heavy days: normal. The get-checked lines: clots larger than about a quarter recurring, soaking a pad or tampon an hour for several hours, periods past 7 days, or a new worsening pattern - those point at fibroids, polyps, adenomyosis, thyroid, or bleeding disorders. And the fatigue companion: heavy periods are a leading cause of iron-deficiency anemia.
What to do
- Apply the quarter rule. Bigger than a quarter, recurring: get checked.
- Apply the pad-an-hour rule. Soaking through hourly for hours: prompt care.
- Check iron with heavy flow. Fatigue plus heavy periods: ask for a blood count.
- Track the pattern. New and worsening over cycles: fibroids and polyps are findable.
Related questions
- Why is my period darker than usual?
- What are fibroids and how do I know?
- Why do I get dizzy on my period?
- Why is my period lighter than usual?