Same week. Every month. Your calendar has been trying to tell you something.

There is a paper calendar on your fridge, under the pizza magnet.

You have been circling the bad days in red since January. You did it to prove something to a doctor.

On a quiet Sunday you flip back through the months. You count. The circles do not scatter across the page. They sit in almost the same week, month after month.

That is a migraine calendar pattern, and you had not noticed it. The pain kept you too busy to notice. For a lot of women, migraines the week before my period, or close to it, are the pattern to look for.

Why do I get migraines every month at the same time?

For many women, the answer is the menstrual cycle.

The American Migraine Foundation says attacks that coincide with the period are common. One of its pages says nearly 2 out of 3 women with migraine have attacks that line up with their period. Another says more than half. Neither page gives a study.

A US survey gives a firmer number. In a 2015 analysis of 1,697 American women with episodic migraine, 5.5% had attacks mostly around the period, and 53.8% had attacks that were menstrually associated. Together that is nearly 60%. The groups were self-reported, not confirmed by diary.

So if your circles cluster, you are in a large group. It may not be coincidence.

What counts as a menstrual migraine?

Doctors use a strict definition. In the International Classification of Headache Disorders, third edition, menstrual migraine appears in the appendix. A 2022 paper in Cephalalgia describes the rule: attacks on day minus 2 to day plus 3 of the period, in at least two out of three cycles. There is no day zero.

The American Migraine Foundation’s page on menstrual migraine puts it in plain words: the window runs from two days before bleeding through the first three days.

There are two types. Pure menstrual migraine means attacks only in that window. Menstrually related migraine means attacks in that window and at other times too. Pure menstrual migraine is the rarer one.

Why migraines get worse before period: the estrogen drop

The usual explanation is a fall in estrogen. The American Migraine Foundation says estrogen drops rapidly just before the period, and stresses the speed of the change more than the level.

Here is the part most pages skip. A 2023 review in the Journal of Headache and Pain, which traces the idea to 1972, calls the evidence for it limited and conflicting. Early studies were small and unblinded, and trials of estrogen gave mixed results. The mechanism is described as unresolved.

So the estrogen drop and migraine link is the accepted working theory, not a settled fact.

Are period migraines worse?

Possibly, with a caveat. The American Migraine Foundation says menstrual attacks tend to be more intense and longer, and may respond less well to acute medication. The review above reports diary studies in which they lasted up to 35% longer.

But the 2015 US survey did not measure duration. It found higher disability scores in the menstrual groups, and it could not show that period attacks are worse than the same woman’s other attacks.

So the honest summary is that they can be harder for some women. It is not guaranteed.

Perimenopause and your migraine pattern

If your cycles are becoming irregular, the calendar gets harder to read. The American Migraine Foundation says perimenopause can make migraine symptoms worse before they get better, because periods become irregular and the hormone shifts are harder to predict.

That is one reason to keep logging, even when the circles stop lining up.

Questions

Why do I get migraines every month at the same time?

For many women the attacks follow the menstrual cycle. In a 2015 US survey of 1,697 women with episodic migraine, about 59% reported attacks that were menstrual or menstrually associated.

What is the definition of a menstrual migraine?

Attacks on day minus 2 to day plus 3 of the period, in at least two out of three cycles, according to the International Classification of Headache Disorders.

Why do migraines get worse before a period?

The accepted theory is a rapid fall in estrogen before the period. A 2023 review calls the evidence for it limited and conflicting.

Are period migraines worse than other migraines?

The American Migraine Foundation says they tend to be more intense and longer. A US survey found higher disability scores, but could not show that they are worse than the same woman’s other attacks.

How do I know if my migraines are tied to my cycle?

Track them in a diary for at least three cycles, noting the first day of your period, the cycle day and when each attack starts.

Can perimenopause make migraines worse?

The American Migraine Foundation says it can, because the hormone shifts become harder to predict.

Where the line comes in

If the attacks gather in one week, the real question is how close your brain sits to the edge when that week arrives.

There is a name for that edge. The Migraine Tipping Line™. The same line for everyone. The difference is how close you sit to it.

Read what the Migraine Tipping Line™ is, and why your diary never found it →

For the other signs that can arrive before the pain, see what is migraine prodrome and how early a migraine can start.