If you get migraines a few times a month, you have probably asked yourself whether that is normal, or whether it is time to do something about it. The answer has a number attached. Doctors divide migraine into episodic and chronic based on how many days a month you have headache, and inside the episodic range there is a threshold where guidelines say prevention should be offered, not just mentioned. Most people never reach that conversation: in a large US study, only about one in four people who qualified for preventive treatment were using it. This guide explains what episodic migraine means, how many migraines a month is too many, what prevention looks like today, and why this exact range of migraine frequency is what current prevention studies are built around.
Tired of planning your life around the next migraine?
These studies are testing new ways to prevent attacks before they start.
What episodic migraine means
Migraine is classified by frequency, counted in headache days per month rather than attacks, because a single attack can last more than a day. Episodic migraine is migraine with fewer than 15 headache days a month. Chronic migraine is 15 or more headache days a month for more than three months, with at least 8 of those days having migraine features. Most people with migraine are in the episodic group, and most trials and treatments are designed around it. The distinction matters because the two are treated and studied differently: some preventive medicines are approved only for chronic migraine, and many prevention trials of new treatments enroll people with episodic migraine specifically.
Episodic migraine is itself a wide range, from one attack a year to a dozen headache days a month. That is why doctors also ask how long attacks last, how severe they are, how well your acute medicine works, and how much the attacks disrupt your life. Two people with four migraines a month can be in very different situations.
How many migraines a month is too many?
There is no "normal" number of migraines, but there is a well defined point at which experts say prevention should be on the table. The American Headache Society's consensus statement puts it in terms of headache days and disability: preventive treatment should be offered at 6 or more headache days a month, at 4 or more if attacks cause some disability, and at 3 or more if the disability is severe, and it should be considered at even lower frequencies when attacks are disabling. The society also advises prevention when attacks significantly interfere with daily life despite acute treatment, when acute medicines do not work or cannot be used, or when they are being used so often that they risk causing more headaches.
A practical way to think about it: if you are having migraines most weeks, if you plan your life around the next attack, or if you are reaching for a triptan or painkiller on more than two days a week, you are past the point where prevention is worth discussing. Keeping a simple diary for a month, noting each headache day, its severity, and what you took, turns that feeling into a number your doctor can act on.
The hidden cost of waiting: medication overuse headache
Treating frequent attacks only as they come has a trap. Taking triptans, ergotamines, opioids, or combination painkillers on 10 or more days a month, or simple painkillers such as ibuprofen or acetaminophen on 15 or more days, can itself cause a daily headache called medication overuse headache, which then makes the migraines harder to treat. The American Headache Society advises limiting acute treatment to an average of two headache days a week and offering prevention to anyone who regularly exceeds that. If your acute medicine is not working well, our guide on what to do when sumatriptan is not working explains the options.
What migraine prevention looks like today
Preventive treatment is taken regularly to make attacks less frequent and less severe, rather than to stop an attack once it starts. For decades it meant repurposed medicines: blood pressure drugs such as propranolol and candesartan, the antidepressant amitriptyline, and the anti seizure medicine topiramate. They help many people, but side effects lead many others to stop. In 2018 the first medicines designed specifically for migraine prevention arrived: monthly or quarterly injections that block CGRP, a molecule central to migraine attacks, followed by CGRP blocking pills. In March 2024 the American Headache Society declared these CGRP targeting therapies a first line option for prevention, no longer requiring that other medicines fail first. Nerve stimulating devices, and for chronic migraine only, botulinum toxin injections, round out the list. Our migraine treatment guide explains each option, and chronic migraine has its own page.
Prevention is judged over months: a treatment is usually given at least two to three months before deciding whether it works, and success is typically defined as cutting migraine days by half. Many people try more than one before finding a fit, which is one reason research continues.
Why episodic migraine is what prevention studies are built around
Trials of new preventive treatments need participants whose migraines are frequent enough to measure a change, but who do not have chronic migraine or medication overuse, because both would blur the result. That is why most prevention studies enroll adults with episodic migraine who have had it for at least a year, have a set number of moderate or severe attacks a month, often between 2 and 10, have fewer than 15 headache days a month, and do not use triptans on 10 or more days. Some also require that your current preventive medicine has been stable for a few months, and most ask that your migraines began before age 50, because headaches that start later need a separate medical evaluation. If you recognized yourself in the "too many" section above, you very likely fit that profile.
In a prevention trial, you keep a migraine diary throughout, which is how the study measures whether the treatment reduces your migraine days. Most trials compare the investigational treatment with a placebo, and acute medicine for attacks is allowed as usual within the limits above. Our guide explains how placebo controlled trials work.
How to find a migraine prevention study
AllClinicalTrials.com lists migraine studies recruiting across the US, from new preventive medicines to device and behavioral research. Right now that includes two prevention studies for adults 18 to 75 with episodic migraine, both for people who have 2 to 10 moderate or severe attacks a month and fewer than 15 headache days a month, and both testing investigational preventive treatments. The application takes about 5 minutes: you answer questions about when your migraines began, how many attacks you have a month, and which medicines you take, and if a study near you looks like a match, the research team contacts you. Nothing is decided until you have gone through informed consent, and participation is voluntary at every step.
Common questions
How many migraines a month is normal? There is no normal number, but guidelines treat 6 or more headache days a month, or 4 or more when attacks are disabling, as the point to offer prevention. Even 2 or 3 severely disabling attacks a month can justify it.
What is the difference between episodic and chronic migraine? Episodic migraine is fewer than 15 headache days a month; chronic migraine is 15 or more for more than three months, at least 8 with migraine features. The two are treated and studied separately.
Can episodic migraine become chronic? Yes. Frequent attacks, overuse of acute medicines, obesity, sleep problems, and depression raise the risk of progression, which is one reason prevention is offered before migraines become chronic.
When should I start migraine prevention? When attacks happen often enough or hurt enough to disrupt your life, when acute medicine does not work or cannot be used, or when you take acute medicine on more than two days a week on average. A headache diary makes the decision much easier.
Do I have to fail other medicines before trying a CGRP treatment? Not according to the American Headache Society, which in 2024 made CGRP targeting therapies a first line option for prevention. Insurance rules vary, so your doctor can advise on access.
Can I join a prevention study if I take a triptan for attacks? Usually yes, as long as you take it on fewer than 10 days a month. Most prevention trials allow your usual acute medicine and ask you to record each use in a diary.
How long does a prevention study last? Typically a few months of treatment plus a baseline month of diary keeping, with visits every few weeks. Each listing gives its own schedule.
See migraine clinical trials recruiting now
Browse open studies, filter by location, and apply in about 5 minutes: Migraine Clinical Trials.