ICHD-3 is the International Classification of Headache Disorders, 3rd edition — the formal criteria the International Headache Society publishes to classify headache disorders. It covers over 200 headache types and is the standard reference for migraine diagnosis worldwide.

What's the difference between ICHD-3 and ICD-11?

ICD-11 is the WHO's general disease classification used for billing and statistics. ICHD-3 is the specialty-specific classification with detailed diagnostic criteria for each headache type. ICD-11 codes for migraine map onto ICHD-3 categories but with less clinical detail.

Why does ICHD-3 matter for migraine?

It defines the diagnostic criteria. The 5-attacks-minimum, 4-72-hour duration, characteristic pain features, and associated symptoms that distinguish migraine from other headaches all come from ICHD-3. Clinicians and researchers use these criteria so they're talking about the same thing.

Can I diagnose myself using ICHD-3?

ICHD-3 is publicly available and you can read the criteria. A formal diagnosis requires a clinician to rule out secondary causes (other conditions presenting as headache) — which is the hard part. ICHD-3 codifies what migraine is; clinical judgment determines whether you have it.

ICHD-3 — the headache classification standard

Creator: Hermly
Published: 2026-05-16T00:00:00.000Z

ICHD-3 is the International Classification of Headache Disorders, 3rd edition — the standardised criteria the International Headache Society publishes for classifying headache disorders. Originally released in 2013 with a beta in 2016 and a finalised version published in Lancet Neurology in 2018, it covers over 200 distinct headache types and is the formal reference used by neurologists, headache specialists, and researchers globally.

It’s the reason a “migraine with aura” diagnosed in Tokyo and one diagnosed in São Paulo refer to the same condition. Without a shared classification, clinical practice and research would fragment.

What ICHD-3 covers

ICHD-3 has three parts:

Part I — Primary headaches

Headaches that are themselves the disorder, not caused by another condition.

1. Migraine — with and without aura, chronic migraine, several rarer subtypes.
2. Tension-type headache — episodic and chronic.
3. Trigeminal autonomic cephalalgias — cluster headache, paroxysmal hemicrania, others.
4. Other primary headaches — exertional, cough, sex-related, primary stabbing.

Part II — Secondary headaches

Headaches caused by another underlying condition.

5–12. Headaches attributed to trauma, vascular disorder, intracranial conditions, substance use or withdrawal, infection, homeostatic disturbance, disorders of the cranium / neck / sinuses / eyes / ears / mouth, or psychiatric disorder.
8.2. Medication overuse headache (MOH) — falls in this section.

Part III — Painful cranial neuropathies, other facial pains, and other headaches

Trigeminal neuralgia, glossopharyngeal neuralgia, and a residual category.

The migraine criteria (most-referenced)

Migraine without aura (ICHD-3 1.1) — the most common type:

A. At least 5 attacks meeting criteria B–D.
B. Duration 4–72 hours (untreated or unsuccessfully treated).
C. At least 2 of: unilateral location, pulsating quality, moderate/severe pain, worsening with routine activity.
D. During headache, at least 1 of: nausea/vomiting, OR both photophobia and phonophobia.
E. Not better accounted for by another ICHD-3 diagnosis.

Migraine with aura (ICHD-3 1.2) — about 25–30% of migraine:

A. At least 2 attacks meeting criteria B–D.
B. ≥ 1 fully reversible aura symptom (visual, sensory, speech/language, motor, brainstem, or retinal).
C. At least 3 of 6 features: gradual development over ≥ 5 minutes, aura symptoms in succession, each lasting 5–60 minutes, at least one unilateral, at least one positive (visual scintillations vs negative scotoma), and headache accompanying or following within 60 minutes.
D. Not better accounted for by another ICHD-3 diagnosis.

Chronic migraine (ICHD-3 1.3):

Headache on ≥ 15 days/month for > 3 months, with ≥ 8 days/month meeting full migraine criteria, in a person with prior migraine history.

These criteria are why your neurologist asks specific questions about attack duration, pain characteristics, and accompanying symptoms — they’re walking through the checklist.

ICHD-3 and Hermly

Hermly is built on the assumption that you have an established diagnosis (formal or working) that fits the ICHD-3 migraine pattern. The prediction model was trained on data from people with recurrent episodic migraine — meaning the 1.1 / 1.2 categories above.

The model is not appropriate for:

Cluster headache (ICHD-3 3.1) — different mechanism, different time course, different treatment.
Tension-type headache (ICHD-3 2.x) — though Hermly may still surface useful weather/sleep correlations, the model isn’t specifically calibrated for it.
Chronic migraine (ICHD-3 1.3) — Empatica 2025 showed prediction models fail entirely on chronic patients. Hermly includes a chronic-frequency gate that returns “prediction unavailable” rather than fabricating a forecast when the pattern doesn’t match the model’s training data. See our methodology page for detail.

The chronic-frequency gate uses ICHD-3 1.3’s 15-day threshold as an event-count proxy — an honest approximation, not a strict ICHD-3 diagnosis.

ICHD-3 vs ICD-11

A frequently confused pair:

ICD-11 is the World Health Organization’s general disease classification, used for medical billing, statistics, and insurance coding. ICD-11 has migraine codes (8A80.x), but with far less clinical detail.
ICHD-3 is the headache-specialty classification with full diagnostic criteria.

In clinical practice, ICD-11 codes are used on insurance claims; ICHD-3 criteria are used in actual diagnosis and treatment decisions. The two are aligned — every ICD-11 migraine code maps to an ICHD-3 category — but ICHD-3 is the source of truth for what the categories mean.

Where to read it

The full ICHD-3 is freely available at ichd-3.org. The 2018 Lancet Neurology publication is the formal reference. Both are intended for clinical and research use, but the criteria themselves are readable by anyone — the medical complexity comes from the differential diagnosis (ruling out secondary causes), not from interpreting the criteria.

Not medical advice. Hermly is a wellness app, not FDA-cleared for diagnosis or treatment. This page is informational and should not replace conversation with your doctor. If you're experiencing a sudden, severe, or unusual headache, contact a medical professional or emergency services.