When something's off
The red flags that tell you something may not be quite right, and the most common conditions behind them.
- 1The red flagsCommon isn't the same as normal. Bleeding between periods or after sex, periods longer than 7 days, cycles outside 21 to 35 days, very heavy bleeding and pain that stops daily life are all reasons to see a doctor.
- 2Heavy periods and anemiaHeavy periods are common but not normal. They can drain the body's iron and cause anemia, and they can be the first sign of a bleeding disorder.
- 3Endometriosis and adenomyosisIn endometriosis, tissue like the uterine lining grows outside the uterus. In adenomyosis, it grows into the uterine wall. Both can cause severe period pain and heavy bleeding, and both often take years to diagnose.
- 4PMOS (PCOS)PMOS, the condition long called PCOS, is a common hormone condition, not a disease of cysts. It can bring irregular periods, acne and extra hair, and it affects metabolism and long-term health. Most people who have it don't know.
- 5FibroidsFibroids are noncancerous growths of the uterine muscle. They're the most common growth in the pelvis. Many cause no symptoms; others cause heavy, painful periods and pressure.
- 6PMDDPMDD is a severe form of PMS that affects about 1 in 20 people who menstruate. Mood symptoms like anger, depression and anxiety come in the week or two before a period and ease once it starts. It is treatable.
- 7Thyroid problems and the cycleThe thyroid, a gland in the neck, affects energy, mood, weight and periods. An underactive thyroid can bring heavier periods; an overactive one can bring lighter or fewer periods. Both are more common in women, and a blood test checks for them.
- 8When a period stopsPregnancy is the first thing to rule out. After that, stress, eating too little, training hard, hormone conditions and some birth control can all stop periods. Missing three in a row is a reason to see a doctor.
- 9For loved onesConditions like endometriosis, PMOS and PMDD often take years to diagnose, partly because pain and symptoms get dismissed. Believe what she tells you, help her track, and back her up at appointments.
- QuizA short quiz on this section. Try again for new questions.
Where can I learn more?
- Wellbeing of Women: "Just a Period" survey results
- Women with endometriosis or adenomyosis face 10- to 11-year diagnostic delays (Contemporary OB/GYN, on a 2026 Journal of Women's Health study)
- ACOG: Dysmenorrhea (painful periods)
- ACOG: Abnormal uterine bleeding
- ACOG: Heavy menstrual bleeding
- Menstrual health education: school health curriculum topics by grade level, J Pediatr Adolesc Gynecol 2025
- NHS: Iron deficiency anaemia
- CDC: About von Willebrand disease
- CDC: Data and statistics on von Willebrand disease
- ACOG: Endometriosis
- WHO: Endometriosis fact sheet (2025)
- Cleveland Clinic: Adenomyosis
- Endocrine Society: PCOS name change (2026)
- WHO: Polycystic ovary syndrome fact sheet (2026)
- Cleveland Clinic: Hyperandrogenism
- Healthed: New evidence-based guideline for PCOS explained
- NHS: Stopped or missed periods
- ACOG: Uterine fibroids
- NHS: Fibroids
- ACOG: Premenstrual syndrome (PMS)
- IAPMD: About PMDD
- Towards understanding the biology of premenstrual dysphoric disorder, Neurosci Biobehav Rev 2023
- American Thyroid Association: Hyperthyroidism
- Menstrual cycle characteristics in women with and without thyroid disease, Cureus 2024
- American Thyroid Association: Hypothyroidism
- Cleveland Clinic: Hypothalamic amenorrhea
- ACOG Committee Opinion 651: Menstruation in girls and adolescents, using the menstrual cycle as a vital sign