You just finished your period. You put the tampons away. Two weeks later, you feel cramps. You go to the bathroom, and—surprise—you’re bleeding again.
This is Short Cycling, also known as “Polymenorrhea.” It is one of the most exhausting phases of the transition because it feels like you are always bleeding, always PMSing, or always recovering.
The Mechanism: The Luteal Phase Defect
A normal cycle has two halves:
- Follicular Phase: Building the egg (variable length).
- Luteal Phase: After ovulation (fixed length, usually 14 days).
In perimenopause, the Luteal Phase often collapses. This happens because the “shell” of the egg (the Corpus Luteum), which produces Progesterone, is weak. It can’t pump out enough progesterone to hold the uterine lining in place for the full two weeks.
Because Progesterone drops too early, the lining sheds prematurely. Instead of a 28-day cycle, you get a 21-day cycle.
The Consequence: The “Double Dip”
Getting two periods in one calendar month is physically draining.
- Iron Depletion: You don’t have enough time to rebuild your red blood cells before you lose them again. This leads to profound fatigue and breathlessness.
- Mood Instability: You are spending twice as much time in the “hormonal crash” zone (the days right before bleeding) and less time in the “happy estrogen” zone.
When to Treat It
If you have one or two short cycles, it’s annoying but normal. If you are short cycling for three months in a row, you need intervention. Your doctor might prescribe Cyclical Progesterone (taken days 14-28) to artificially lengthen the luteal phase. This “holds” the lining in place so you don’t bleed until you stop the medication, restoring a 28-day rhythm and giving your body a break.