What Counts as a Migraine Day? The Rules Trials Use

A migraine day is a calendar day, not an attack. That single distinction is why your count and your neurologist’s count can come out a third apart, and why an attack that starts at nine on Tuesday evening and finally lifts at three on Thursday morning is three migraine days rather than one.

Nobody makes this up locally. Before anyone could claim a preventive cut migraine days in half, drug trials had to agree on what one was, and the International Headache Society publishes the counting rules its trials run on. Those rules then leak into everything downstream — the 15-day chronic threshold, the Botox licence, the 50% response your neurologist is looking for at the eight-week review. If you count differently from the definition behind the threshold, you get the wrong answer about your own treatment.

The definition, in one sentence

A migraine day is a calendar day on which you had a headache with migraine features that lasted four hours or more — or one of any duration that you treated with a migraine-specific drug such as a triptan. Attacks that came with aura qualify from thirty minutes, not four hours.

Three things fall out of that sentence, and each one catches people out.

A long attack is more than one day

The unit is the day, not the episode. An attack that begins at 9pm on Tuesday, keeps you in a dark room through Wednesday, and eases at 3am on Thursday touches three calendar days. That is three migraine days.

This is the single most common undercount. People think in attacks because that is how the experience feels — one bad thing that happened once — and write “1” in the box. A neurologist reading that number thinks you lost one day that month. You lost the better part of three.

The reverse error exists too. If you had a two-hour headache on Monday morning and another on Monday night, that is one migraine day. Two attacks, one day. Both numbers are worth having, which is why a good diary records attacks and lets the days be counted from them, rather than asking you to do arithmetic while you feel awful.

The four-hour floor, and the exception that undoes it

Untreated, a migraine attack in an adult is defined as lasting four to seventy-two hours. The four-hour floor in the counting rule comes straight from that.

Then comes the exception that matters more than the rule: a headache of any duration counts if you treated it with a migraine-specific medication. You felt it coming at 7:40am, took a triptan at 8:00, and were functional by 10:30. Ninety minutes of pain. It counts as a migraine day.

People routinely leave these out, and it is the worst possible thing to leave out. Treating early is what you are supposed to do. A diary that only records the attacks you failed to stop makes an effective acute drug look like an absent problem, and makes you look like you have fewer migraine days than you are actually having. It also quietly hides how often you are medicating, which is the number that matters for medication overuse headache, where the threshold for triptans is ten days a month rather than fifteen.

Recurrence inside 48 hours is the same attack

You wake up clear. By late afternoon it is back. Is that a second attack?

For counting purposes, no. An attack that remits and then returns within 48 hours is treated as one attack that relapsed, not two attacks. Sleep interrupting it doesn’t restart the clock either.

But — and this is where people over-correct — the days still count separately. One attack across Friday and Sunday with a clear Saturday gives you two migraine days from one attack. Attack counts and day counts answer different questions, and the second is the one thresholds are written in. The pattern itself is worth logging as such; recurrence within a couple of days is common enough to have a name, and there’s more on why a migraine comes back once you can see it happening in your own record.

Headache days and migraine days are different numbers

Chronic migraine is not “fifteen migraine days a month”. It is headache on 15 or more days a month for more than three months, of which at least 8 have migraine features or responded to a triptan. Two numbers, and the ICHD-3 definition of chronic migraine needs both.

So the tension-type day where your head aches dully all afternoon is a headache day and not a migraine day. It still belongs in the diary. Leave those days out and you can sit at 14 headache days for a year without anyone noticing you meet a definition that changes which treatments you qualify for. This is the whole reason the chronic threshold takes two numbers rather than one.

What doesn’t count, and what to log anyway

Aura with no headache at all is not a migraine day under the trial definition — the endpoint is built on headache. Log it anyway, dated, with what you saw and how long it lasted. It’s clinically meaningful even when it doesn’t score.

The postdrome day is the same case. The day after, when you’re wrung out and slow and not in pain, isn’t a migraine day in the counting sense. It is very much a lost day, and if you’re building a case for accommodations or a benefits claim, lost days are the currency. Keep it in a separate column rather than folding it into the count, so the number you hand a clinician still means what they think it means.

Record it so you never have to reconstruct it

Reconstruction is where accuracy dies. On the last Sunday of the month, nobody remembers whether the bad one started Tuesday night or Wednesday morning, and the difference is a whole migraine day.

Three fields make the count fall out on its own:

• Start date and time — not “Tuesday”, the actual time, because that’s what decides whether one day or two.
• End date and time, or “still going” — filled in when it ends, not estimated later.
• What you took and when — because that’s what turns a ninety-minute headache into a counted day.

On paper, a printable diary with a row per attack and a column for the medication does it. Migraine Journal records the start time when you log and computes migraine days per month from the entries, which is the number its doctor report leads with. Either way, the discipline is the same: log the attack when it starts, not when you feel well enough to be tidy.

If your count changes materially once you start applying these rules — and for most people it goes up — that’s worth raising with whoever prescribes for you, because several thresholds sit between 8 and 15 days and you may have been on the wrong side of one on paper only.