Your cycle is a vital sign

Doctors check your pulse, temperature and blood pressure because they say something about your overall health. Some medical bodies say your cycle belongs on that list too. The American College of Obstetricians and Gynecologists has called the menstrual cycle a "vital sign", and a 2025 review in The Lancet Obstetrics, Gynaecology and Women's Health made the same case across the whole lifespan.

This does not mean every wobble is a problem. It means a lasting change in your pattern is worth noticing, because it can be an early clue to things like thyroid problems, low energy intake, PMOS, fibroids or low iron.

Patterns worth noticing

• Cycles regularly shorter than 21 days or longer than 35 days (NHS).
• Your usual pattern changing and staying changed.
• Periods lasting more than 7 days.
• Needing to change a pad or tampon every 1 to 2 hours, or passing clots bigger than about 2.5 cm (the size of a 10p coin).
• Bleeding between periods, or any bleeding that is unusual for you.
• Missing 3 periods in a row, or no period by age 15.
• Pain that stops you doing normal things, or gets worse over time.

What to bring to an appointment

1. Start dates of your last 3 to 6 periods and how long each lasted.
2. How heavy: how often you change products, clots, flooding or leaks.
3. Pain: when, how bad, and what it stops you doing (work, school, exercise, sleep).
4. Any bleeding outside your period.
5. Any medicines, supplements or hormones you take.
6. What matters most to you. NICE says heavy periods should be judged by their effect on your quality of life, not just the amount of blood.