Aimovig can start reducing migraine frequency within the first week of treatment, though most people notice meaningful improvement over the first one to three months. The medication reaches steady levels in your blood by about three months, which is when you can best judge whether it’s working for you.
The First Few Weeks
Clinical studies in migraine patients found that Aimovig produced a statistically significant reduction in weekly migraine days as early as week one after the first injection. In one study, patients on the 140 mg dose saw their weekly migraine days drop by about half a day more than placebo within that first week alone. For people with chronic migraine (15 or more headache days per month), the difference from placebo became clear by week two.
These early reductions were sustained through the rest of the first month. So while Aimovig isn’t an instant fix, many people do experience some relief before their second injection is due.
When You’ll See the Full Effect
Your body needs about three months of regular monthly injections for Aimovig to reach steady-state levels in your blood. The medication has a half-life of 28 days, meaning each dose is still partially active when the next one arrives, and the drug gradually builds to a consistent concentration.
In the ARISE trial, patients on the 70 mg dose experienced about 2.9 fewer migraine days per month compared to 1.8 fewer days for placebo. That roughly one-day advantage over placebo may sound modest, but it reflects an average across all participants, including those who responded strongly and those who didn’t respond at all. Many individual patients see much larger reductions.
Most headache specialists recommend using Aimovig for at least three months before deciding whether it’s effective. Some people respond dramatically in month one, others see gradual improvement that becomes clear only by month two or three. Stopping after a single injection that didn’t seem life-changing could mean giving up on a treatment that would have worked with a little more time.
Long-Term Results
For people who do respond, the benefits hold up over years. A five-year open-label study tracked 383 patients and found that migraine frequency dropped by an average of 62.3% from a baseline of about 8.7 migraine days per month. That’s a reduction of roughly 5.3 days per month sustained through year five. Patients who were using acute migraine medications (triptans, pain relievers) at baseline also cut their use by about 4.4 days per month over the same period. Improvements in disability scores and quality of life remained stable throughout.
Safety also stayed consistent over five years, with no new concerns emerging. The most common side effects were ordinary infections like colds and flu, not medication-specific problems.
How Aimovig Works Differently
Aimovig is the only approved migraine prevention antibody that targets the CGRP receptor itself rather than the CGRP molecule floating in your bloodstream. CGRP is a protein involved in transmitting pain signals during migraine attacks. Other antibody treatments (fremanezumab, galcanezumab, eptinezumab) grab onto the CGRP protein before it can reach the receptor. Aimovig instead parks on the receptor and blocks CGRP from docking there.
This distinction matters because Aimovig binds to about 98% of cells that carry the CGRP receptor, and it also blocks a related receptor involved in pain signaling. The other antibodies don’t interact with that second receptor at all. Whether this translates to a meaningful clinical difference for any individual patient isn’t fully settled, but it does mean Aimovig’s mechanism is broader than simply neutralizing one protein.
What to Expect in the First Months
The most common side effects during early treatment are constipation, fatigue, nasal congestion, injection site reactions (pain, redness, or mild swelling), muscle spasms, and itching. Constipation is probably the most frequently reported complaint and is usually mild. Rarely, constipation can become severe, so persistent abdominal pain, vomiting, or bloating warrants a call to your doctor.
Allergic reactions are uncommon but can occur within minutes of the injection or, in some cases, more than a week later. Signs include rash, swelling, or difficulty breathing.
One practical note: Aimovig is a once-monthly self-injection using an autoinjector pen. The injection itself takes about 15 seconds. There’s no loading dose or ramp-up period. You start at either 70 mg or 140 mg and stay at that dose. If 70 mg provides partial but insufficient relief after a few months, your prescriber may move you to 140 mg.
Tracking Whether It’s Working
Because Aimovig’s benefits build gradually, keeping a migraine diary during your first three months is one of the most useful things you can do. Record the number of migraine days per month, their severity, and how many doses of acute medication you take. Without a written record, it’s easy to overlook a meaningful improvement, like going from 10 migraine days to 7, that you might not notice in real time but that shows up clearly in the numbers.
If your migraine days haven’t decreased at all after three full months, Aimovig is unlikely to be your best option. But if you’re seeing partial improvement, staying on it longer or adjusting the dose may yield further gains, since long-term data shows continued improvement well beyond the three-month mark for responders.