How Many Migraine Days to Qualify for Botox?

Fifteen or more headache days a month, at least eight of them with migraine features, for more than three months. That is the ICHD-3 definition of chronic migraine, and chronic migraine is the only headache condition Botox is licensed to prevent. The FDA label specifies adults with 15 or more headache days a month, each lasting four hours or longer, and states that effectiveness has not been established for anyone below that line.

So the answer has two parts. The threshold is fifteen-and-eight. And no neurologist can act on the threshold itself — only on a record showing you have met it, month after month. The appointment where Botox or a CGRP drug gets discussed is, in practice, an audit of that record.

What counts as a headache day on the form

A headache day is a calendar day, not an attack. An attack that starts Tuesday night and clears Thursday morning is one attack and three headache days. Days you treated early and got through fine still count. So does waking with a headache and losing it by eleven, provided it ran four hours.

The eight migrainous days are the stricter test: days meeting the migraine criteria, or days you believed were migraine at onset and that a triptan or ergot resolved. Plain dull-headache days count toward the fifteen but not the eight. How the two numbers interact — and the four ways people miscount them — is its own subject; the short version is that most people undercount, because the days that went well are the days they forget.

Why the written record outweighs your memory

“Most days, honestly” is not a number a clinician can write in your chart, and the chart is what every subsequent decision runs on. ICHD-3 itself says that characterising frequently recurring headache generally requires a diary kept day by day for at least one month. That is the classification behind the diagnosis naming a diary as part of the diagnostic method, not a tracking blog telling you to journal.

There is a second reason the record matters more than your memory. In both the US and the UK, someone other than your neurologist reviews the paperwork before treatment is funded. Exactly what that reviewer asks for varies — by insurer and plan in the US, by trust and pathway in the UK — but the common factor is that they were not in the room and cannot weigh how credible you sounded. They work from what was written down. A month you lived through but never recorded is, for this specific purpose, a month that is hard to count.

Whether your record meets the definition is a judgement your neurologist makes, not one to settle from a blog post; the diary’s job is to let them make it in minutes instead of asking you to reconstruct three months in the waiting room.

The five things the record has to show

• Headache days per calendar month, for at least three consecutive months. Not attacks — days. The three-month duration is in the ICHD-3 criteria, so one bad month proves nothing on its own.
• Which of those days were migrainous. The eight-day criterion needs the symptom detail (or the triptan response) recorded on the day, not recalled later.
• How long each headache lasted. The FDA definition’s four-hour clause means a diary that only records “headache: yes” is missing a field the label asks about.
• Every day you took an acute medication, by type. Fifteen treated days a month almost certainly crosses the medication-overuse thresholds: 10 days a month for triptans, ergots, opioids and combination painkillers, 15 for plain analgesics. NICE’s Botox guidance requires medication overuse to be appropriately managed before treatment, and ICHD-3 notes that around half of apparent chronic migraine reverts to episodic once an overused drug is withdrawn. Your medication days are not a side note; they are the first thing checked.
• Every preventive you have already tried — the drug, the dose you reached, how many weeks you stayed on it, and why it ended (no effect, or side effects you could not live with). “I tried propranolol once, it didn’t help” is unusable. “Propranolol, 12 weeks, stopped for fatigue” is a line on a prior-authorisation form.

That last item is the one nobody keeps in real time, because a preventive that failed two years ago feels like history. Write it down now, while you still remember the year. It also matters that those weeks were enough weeks — how long a preventive needs before it can fairly be called a failure is the difference between a trial that counts on a prior-authorisation form and one that gets waved away.

The US and the UK ask for different proof

In the UK, NICE TA260 funds Botox only for chronic migraine as defined above, only after at least three preventive medicines have failed, not been tolerated, or been unsuitable — and treatment stops if headache days have not fallen 30% after two cycles, so the diary keeps working after approval, not just before it. The CGRP monoclonal antibodies sit under separate appraisals with a lower frequency bar: erenumab, for example, requires 4 or more migraine days a month plus the same three failed preventives. In the US, the FDA licence is the eligibility floor and coverage runs through your insurer’s prior authorisation. Those policies were largely built on the American Headache Society’s older consensus — roughly two preventive classes tried for about eight weeks each — and the AHS’s 2024 position statement now argues CGRP therapies should be a first-line option with no prior-failure requirement at all. A position statement is not a coverage policy, though, and whether your plan has caught up is a question your neurologist’s office answers case by case. The documentation that settles it is the same either way.

Doing it on paper

A wall calendar and two marks per day is enough: an H on any headache day (add an M if it was migrainous, and roughly how many hours), and the initial of anything you took. At the end of each month, write three totals in the corner: headache days, migrainous days, medication days. Three corners filled is a record a neurologist can use. Keep the failed-preventives list on the back page.

The failure mode of paper is the gap — the bad week you were too ill to write anything is exactly the week the count needs. An app closes that gap by making the entry a ten-second act from bed; Migraine Journal, for instance, totals headache days and medication days per calendar month automatically, which are two of the three numbers this whole process turns on. The rest of the tracking guides cover what else a diary can carry into an appointment.

If you’re in the US, the count has a second audience after your neurologist agrees. Insurers decide against their own written criteria, and what a CGRP prior authorization asks your diary to show covers the baseline period, the prior-drug table, and the renewal trap that catches people who started treatment without recording the month before.

Start the calendar today, not on the first of the month. Three months from now is soon enough to have the conversation; it is too late to start the record.