Mittelschmerz: what it means

Mittelschmerz is the medical term for the one-sided pain some people feel around ovulation, roughly two weeks before a period. The word comes from German for "middle pain," because it shows up in the middle of the cycle rather than near the period itself.

It usually shows up as:

• A dull ache or a sharp twinge low on one side of your belly
• Pain that lasts a few minutes to about a day or two
• A switch in sides from month to month, depending on which ovary releases the egg
• Sometimes light spotting or a small change in discharge around the same time

Not everyone notices ovulation at all, and mittelschmerz on its own isn't a problem. Doctors think it comes from the follicle stretching right before it releases an egg, or from the small amount of fluid that follows.

Mittelschmerz happens at ovulation. PMS and PMDD happen later, in the luteal phase, the one to two weeks between ovulation and your period. They're different events in the same cycle, not the same thing.

Some people use mittelschmerz as a marker. Once that twinge passes, they know the luteal phase, and the window where PMS or PMDD symptoms can build, is starting. For how estrogen and progesterone shift across these phases, see menstrual cycle hormones, phase by phase.

Knowing mittelschmerz is separate from PMS or PMDD matters because it changes what you're treating. Pain at ovulation usually needs nothing more than rest and a way to manage the ache. Mood or physical symptoms that show up later, as the corpus luteum forms and then breaks down, have a different cause.

What can help with mittelschmerz pain right now:

• A heating pad or warm bath on the side that hurts
• An over-the-counter pain reliever, if your doctor says it's fine for you
• Rest if the ache is sharp enough to need it

Niyora is a PMS and PMDD support app. Niyora's estimated PMS window can give you a sense of when the luteal phase, and PMS or PMDD symptoms, might start, without you tracking it yourself.

A few terms often come up alongside mittelschmerz:

• Corpus luteum: the structure that forms after ovulation and makes progesterone.
• Allopregnanolone: a hormone byproduct linked to mood changes in the luteal phase.
• Menstrual cycle hormones, phase by phase: how estrogen and progesterone shift across the month.

Knowing these terms makes it easier to tell a normal cycle sensation from a symptom worth tracking with your doctor. For the fuller picture on what causes PMDD, see PMDD, explained and PMS and PMDD research, summarised.