Is My Migraine Preventive Working? Response Calculator
Compare your migraine days before and after starting a preventive, see your percent reduction, and check whether you’ve given it a fair trial.
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Starting a preventive is a bit of an experiment, and it’s hard to judge from inside a bad month. The fairest way is to compare your migraine days before and after, at the right point in time. This calculator does the math, tells you whether you’ve given the treatment long enough, and shows how your result compares with the benchmarks doctors use.
Loading the calculator. If it doesn’t appear, check that JavaScript is turned on. The guide below lets you work it out by hand.
How long does a migraine preventive take to work?
| Preventive | Fair trial before judging |
|---|---|
| Daily pills (topiramate, propranolol, amitriptyline, candesartan and others) | 8 to 12 weeks at the target dose |
| Gepants for prevention (atogepant, rimegepant) | About 12 weeks |
| Monthly CGRP antibody | 3 months |
| CGRP antibody every 3 months | 6 months (2 doses) |
| Botox (onabotulinumtoxinA) | About 24 weeks (2 treatment sessions) |
The pill and Botox timings follow the 2026 AAN and American Headache Society guideline. The CGRP antibody timings follow the American Headache Society’s consensus statements (2019, updated 2021).
What counts as a preventive working?
- 50% fewer migraine days is the standard benchmark for a good response, and the main outcome in most preventive trials.
- 30% fewer is often counted as a meaningful response in chronic migraine.
- Quality of life counts too. When deciding whether to keep going with a CGRP preventive, the American Headache Society also accepts a meaningful drop in MIDAS (5 points or more from a score of 11 to 20, or 30% or more from a score above 20) or a HIT-6 drop of 5 points or more. These make a reasonable yardstick for any preventive.
If you have before and after scores, add them in the optional section. You can get them from our MIDAS calculator and HIT-6 calculator.
If it isn’t working
Not responding to one doesn’t mean the next won’t work. Many people find a good fit on their second or third try. There are several classes that work in different ways. Our guide to which preventives work best lays out the options. Side effects that are hard to live with are also a perfectly good reason to switch.
Frequently asked questions
How do you calculate the percent reduction in migraine days?
Take your migraine days a month before starting, subtract your days now, and divide by the starting number. For example, going from 10 to 4 days is a 6-day drop, and 6 divided by 10 is a 60% reduction.
How long should I try a preventive before giving up?
For daily pills, 8 to 12 weeks at the target dose. For monthly CGRP antibodies, 3 months. For quarterly CGRP antibodies, 6 months. For Botox, about 24 weeks, which is 2 treatment sessions.
Is a 30% reduction in migraine days good?
It’s often counted as a meaningful response, especially in chronic migraine. Whether it’s good enough depends on how you feel, your side effects, and what other options you have.
Should I stop my preventive if it works?
Not on your own. If things have been stable for 6 to 12 months, ask your doctor whether a lower dose or a planned break makes sense.
More free migraine tools
- MIDAS CalculatorMigraine disability score from 5 questions about the last 3 months.
- HIT-6 CalculatorHeadache Impact Test score from 6 quick questions.
- Migraine Screening TestDo your headaches look like migraine? The 3-question ID Migraine.
- Chronic Migraine CalculatorEpisodic or chronic? Check your monthly headache days.
- Medication Overuse Headache CheckerRebound headache check against the ICHD-3 day limits.
- Preventive Response CalculatorPercent drop in migraine days, and is it a fair trial yet?
- Caffeine CalculatorTotal your daily caffeine and see where it lands for migraine.
- Visit Summary BuilderA one-page printable summary for your doctor or neurologist.
References
- Potrebic S, Tanveer S, Becker WJ, et al. Pharmacologic treatment for migraine prevention in adults: practice guideline recommendations. Report of the AAN Guidelines Subcommittee and the American Headache Society. Neurology. 2026;107(7):e214881. doi:10.1212/WNL.0000000000214881
- Ailani J, Burch RC, Robbins MS; Board of Directors of the American Headache Society. The American Headache Society Consensus Statement: Update on integrating new migraine treatments into clinical practice. Headache. 2021;61(7):1021-1039. PubMed
- American Headache Society. The American Headache Society position statement on integrating new migraine treatments into clinical practice. Headache. 2019;59(1):1-18. PubMed
This tool is for education and to help you talk with your doctor. It doesn’t diagnose anything and isn’t medical advice. Your answers stay in your browser and are never sent to Cerebral Torque.
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