How many headache days a month count as chronic migraine?

Under ICHD-3, chronic migraine means headache on 15 or more days a month for more than 3 months, with the features of migraine on at least 8 of those days, in a person who has had typical migraine attacks before. Fewer than 15 days a month is episodic migraine, according to NICE. Only a doctor can make the diagnosis.

Facts checked on · Written by Alfonso Matos, the developer of MyGrain.

The ICHD-3 definition

ICHD-3 criteria for 1.3 Chronic migraine require headache, migraine-like or tension-type-like, on 15 or more days a month for more than 3 months, in a person who has had at least five attacks of migraine without aura and/or attacks of migraine with aura. On at least 8 days a month for more than 3 months the headache must meet migraine criteria, or be believed by the person to be migraine at onset and be relieved by a triptan or ergot derivative. The headache must not be better accounted for by another diagnosis.

What counts as a headache day

ICHD-3 notes that in chronic migraine, attacks with and without aura are both counted, as are both migraine-like and tension-type-like headaches, but not secondary headaches. It explains why the category exists: in people with such frequent or continuous headaches it is impossible to distinguish individual episodes, and the characteristics of the headache may change from day to day or even within the same day. NICE defines episodic migraine as occurring on fewer than 15 days per month.

Counting the days in your diary

ICHD-3 states that characterizing frequently recurring headache generally requires a headache diary recording pain and associated symptoms day by day for at least one month. For each month, note:

  • the number of days with any headache;
  • how many of them had migraine features (one-sided or pulsating pain, nausea, sensitivity to light and sound, as in the migraine criteria);
  • the days on which you took medication for it, since ICHD-3 notes that medication overuse is the most common cause of symptoms suggestive of chronic migraine.

Because the definition refers to more than 3 months, a single month above 15 days does not by itself meet it.

Why the medication count goes alongside

ICHD-3 notes that around 50% of patients apparently with chronic migraine revert to an episodic type after drug withdrawal, and that people who meet criteria for both chronic migraine and medication-overuse headache are coded for both. In MyGrain you can log each episode with its type, intensity, symptoms and treatments, see the days on a calendar and take that record to your appointment. MyGrain does not diagnose: only a doctor can diagnose chronic migraine.

Frequently asked questions

Is 15 headache days a month always chronic migraine?

No. ICHD-3 also requires it to last more than 3 months, at least 8 of those days to have migraine features, and a history of migraine attacks. The headache must not be better explained by another diagnosis.

What is episodic migraine, then?

NICE describes the headaches of episodic migraine, with or without aura, as occurring on fewer than 15 days per month.

Do tension-type headaches count towards the 15 days?

Yes. ICHD-3 says that for chronic migraine both migraine-like and tension-type-like headaches are counted, but not secondary headaches.

How long should I record before knowing my count?

ICHD-3 says a diary of at least one month, day by day, is generally needed to characterize frequent headache. The definition itself refers to more than 3 months.

Sources

Classification criteria and NICE guideline, re-read on .

Medical disclaimer. MyGrain is a self-tracking diary, not a medical device. It is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your doctor or another qualified health professional with any question about a medical condition.
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