Headache is on the list of semaglutide side effects, but the trial numbers put it in proportion. In the main weight trials, it was only a little more common on the drug than on placebo.
This article sets out what the labels recorded, where headache overlaps with other warnings, and what studies of GLP-1 drugs in headache disorders found. The broader list is in semaglutide side effects.
How often did it happen in trials?
The Wegovy label reports headache in three sets of placebo-controlled trials [1]. Each row below is the share of people who reported it at least once.
| Trials and dose | Semaglutide | Placebo |
|---|---|---|
| Adults, 2.4 mg weekly (n = 2,116 vs 1,261) | 14% | 10% |
| Adults, 7.2 mg weekly (n = 1,311 vs 303) | 9% | 7% |
| Adults, 2.4 mg arm of the 7.2 mg trials (n = 304) | 8% | 7% |
| Ages 12 and up, 2.4 mg weekly (n = 133 vs 67) | 17% | 16% |
So in the largest adult pool, about 4 extra people in 100 reported a headache on the drug. In the higher-dose trials and in teenagers, the difference was 1 to 2 points.
The Ozempic label, from its diabetes trials, lists reactions seen in at least 5% of patients [2]. Headache is not among them. Its post-approval section does list headache among voluntary reports, where the true rate cannot be estimated.
The Zepbound label for tirzepatide does not list headache in its table of common reactions [3].
Where headache overlaps with other warnings
The labels do not say why semaglutide might cause a headache. They do name headache in one specific place.
Both the Wegovy and Zepbound patient information list headache among the signs of low blood sugar [1] [3]. The risk of low blood sugar is higher when these drugs are used with insulin or a sulfonylurea.
The labels also warn that nausea, vomiting and diarrhea can cause dehydration. That is a reason those symptoms are worth reporting when they persist, as covered in Ozempic nausea and tirzepatide diarrhea.
What studies in headache disorders found
Here the evidence runs in the opposite direction. It comes mostly from other GLP-1 drugs, small groups and specific headache disorders, so it does not say what semaglutide does for an ordinary headache.
Idiopathic intracranial hypertension is raised pressure inside the skull with no clear cause. In a randomized trial of 16 women with obesity and active disease, the GLP-1 drug exenatide lowered that pressure against placebo [4].
The drop was 5.7 cm of cerebrospinal fluid at 2.5 hours and 6.4 at 24 hours. At 12 weeks it was 5.6, with P = 0.058 against a pre-set threshold of 0.1.
An open-label pilot followed 39 people with the same condition [5]. The 13 who chose semaglutide or liraglutide lost 12.0% of body weight at 6 months, against 2.8% in matched controls.
Their median monthly headache days fell by 4, against no change in controls. Half or more of headache days were gone in 76.9% of the drug group, against 40.0% of controls.
In migraine, one open-label pilot gave liraglutide 1.2 mg daily to 31 people with obesity and hard-to-treat migraine [6]. Monthly headache days fell from 19.8 to 10.7 over 12 weeks.
Body mass index barely moved in that study, so the authors propose an effect separate from weight loss. There was no placebo group, which limits what the result can show.
A 2024 systematic review of GLP-1 drugs in headache and pain pooled 42 studies, both animal and human [7]. It describes GLP-1 as involved in migraine mechanisms, with benefits so far in idiopathic intracranial hypertension.
Putting it together
Headache on semaglutide is real but modest in the trials, and it was close to the placebo rate at 7.2 mg. The labels give no mechanism for it.
None of the studies above is a randomized trial of semaglutide in migraine. The dose steps that coincide with most side effects are laid out in semaglutide dosage.
For another GLP-1 drug, see liraglutide side effects. To compare prescribers, see the compounded semaglutide rankings.