Lifestyle, cycles
Your cycle has four phases, not four equal weeks
The tidy 28-day circle in the textbook describes almost nobody. Here is what actually happens, and which part moves when your cycle changes.
Reviewed against NHS, 1 min read, published
You have seen the diagram: a circle, four equal wedges, 28 days. It is a decent teaching tool and a poor description of a real person.
What happens in each phase
- Period: day one is the first day of proper flow — spotting the day before does not count. The lining sheds because oestrogen and progesterone have both dropped away.
- Follicular phase: a handful of follicles start maturing, one takes the lead, and oestrogen climbs as the lining rebuilds.
- Ovulation: a surge of another hormone releases the egg.
- Luteal phase: the steady one. It tends to run about the same length every month.
The length of the menstrual cycle varies from woman to woman, but the average is to have periods around every 28 days.
Why your cycle length changes
Quick summary
- Day one: the first day of proper flow, not spotting
- First half: the part that stretches and shrinks, before ovulation
- Second half: runs about the same length every month
- A late period: stress or illness can delay ovulation without anything being wrong
