Migraines are diagnosed based on your symptoms and medical history, not a blood test or brain scan. There is no single test that confirms a migraine. Instead, doctors match your pattern of attacks against a well-established set of criteria, rule out other causes, and may perform a neurological exam to make sure nothing else is going on.
The Criteria Doctors Use
The formal diagnostic standard comes from the International Classification of Headache Disorders, now in its third edition. For the most common type, migraine without aura, you need to have experienced at least five attacks that meet a specific pattern. Each attack lasts between 4 and 72 hours if untreated (or 2 to 72 hours in children and teens). The headache itself must have at least two of these four features: pain on one side of the head, a pulsating or throbbing quality, moderate to severe intensity, or pain that gets worse with routine physical activity like walking or climbing stairs.
On top of the pain characteristics, you also need at least one accompanying symptom during the headache: either nausea or vomiting, or sensitivity to both light and sound. If your attacks check these boxes and nothing else better explains them, that’s a migraine diagnosis.
These criteria might sound rigid, but they exist because migraine overlaps with other headache types. Tension-type headaches, for example, are essentially defined by the absence of migraine features. They tend to cause pressing or tightening pain on both sides of the head, at mild to moderate intensity, without nausea or vomiting, and they don’t get worse when you move around. In practice, the line between the two can blur. Up to a quarter of people with tension-type headaches report that physical activity makes their pain worse, and some experience one-sided pain. That overlap is exactly why tracking your symptoms carefully matters so much.
How Migraine with Aura Is Identified
About a quarter to a third of people with migraine experience aura, a set of reversible neurological symptoms that typically appear before or alongside the headache. Visual aura is the most common type. It often shows up as a zigzag or shimmering pattern near the center of your vision that gradually spreads outward, sometimes leaving a temporary blind spot behind it. Next most common are sensory disturbances, usually pins and needles that slowly travel across one side of the body, the face, or the tongue. Some people experience speech difficulties instead.
The key diagnostic features of aura involve timing and progression. At least one symptom should spread gradually over five minutes or more. Each individual symptom lasts between 5 and 60 minutes. At least one symptom is one-sided, and the aura is followed by a headache within 60 minutes (or accompanies it). The gradual onset is important because it distinguishes migraine aura from the sudden neurological symptoms of a stroke, which come on all at once rather than building over minutes.
What Happens During the Exam
Your doctor will take a detailed history of your attacks and then perform a neurological examination. This typically includes checking your mental status, motor strength, reflexes, and vision. The doctor may test the cranial nerves connected to your brainstem by assessing facial sensation, hearing, eye movements, and your ability to swallow and move your head and shoulders. They may also look at the back of your eye for any signs of swelling of the optic nerve, which could indicate increased pressure inside the skull.
If your neurological exam is normal and your headache pattern matches the migraine criteria, that’s usually enough. No scan or lab work is needed to confirm the diagnosis.
When Brain Imaging Is Recommended
Updated guidelines from the American Headache Society are clear: neuroimaging is not necessary for patients whose headaches are consistent with migraine and who have a normal neurological exam. A brain MRI or CT scan is reserved for situations where something about the presentation raises concern.
Imaging may be considered if you have unusual, prolonged, or persistent aura. It’s also warranted for a first or worst migraine, attacks that are increasing in frequency or severity, headaches that always occur on the same side, migraine with brainstem aura, hemiplegic migraine (where you experience temporary weakness), migraine aura without any headache, or migraine that starts after a head injury. If your doctor orders imaging, it’s not because they expect to find something dangerous. It’s a precaution to rule out secondary causes.
Red Flags That Prompt Further Testing
Doctors use a set of warning signs, sometimes remembered by the mnemonic SNOOP, to decide whether a headache might have a secondary cause that needs investigation.
- Systemic symptoms or illness: Fever, night sweats, weight loss, or an underlying condition like a compromised immune system.
- Neurological symptoms: New weakness in an arm or leg, new numbness, or visual changes that don’t fit a typical aura pattern.
- Sudden onset: A headache that reaches maximum intensity within seconds, sometimes called a thunderclap headache, is one of the most concerning red flags. It can point to a vascular problem like an aneurysm and needs immediate evaluation.
- Older age of onset: A brand-new headache pattern starting after age 50 is more likely to have a secondary cause.
- Progression: Headaches that are clearly becoming more severe or more frequent over time.
- Positional changes: Pain that shifts in intensity when you stand up or lie down, or that’s triggered by coughing or straining, can indicate a pressure-related problem.
- Pregnancy: New headaches during or after pregnancy warrant evaluation for vascular or hormonal complications.
None of these red flags automatically mean something serious is wrong. They simply tell your doctor that the headache needs more investigation before it can be attributed to migraine alone.
Episodic vs. Chronic Migraine
Once you have a migraine diagnosis, the next distinction is whether it’s episodic or chronic. Chronic migraine is defined as having headaches on 15 or more days per month for more than three months, with at least 8 of those days meeting the full criteria for migraine or responding to migraine-specific medication. The remaining headache days can feel more like tension-type headaches, which is common as migraine becomes chronic. This classification matters because it changes treatment strategy, and qualifying as chronic may open the door to preventive therapies that aren’t typically offered for less frequent attacks.
How a Headache Diary Helps
Because diagnosis depends entirely on your symptom history, the single most useful thing you can do before your appointment is keep a headache diary. A well-designed diary, like the one used by Mayo Clinic, tracks the variables a doctor needs to see: the date and number of headaches, pain severity on a 0 to 10 scale, total duration, and whether the pain was one-sided or throbbing.
Beyond the pain itself, you should note associated symptoms: whether you experienced aura (visual disturbances, tingling, speech problems), nausea, vomiting, light sensitivity, sound sensitivity, and whether physical activity made the headache worse. Track any medications you took and whether they helped. If you menstruate, note the timing of your period, spotting, or oral contraceptive use, since hormonal patterns are a major migraine trigger that can only be identified over several cycles.
Prodrome symptoms are also worth recording. Some people reliably experience yawning, nausea, or light sensitivity hours before the pain starts. Identifying a prodrome can strengthen the diagnosis and eventually help you recognize an attack early enough to treat it more effectively. Even two to three months of consistent tracking gives a doctor a far clearer picture than trying to recall your headache history from memory during a 15-minute appointment.