Where headache appears in the labels
- Wegovy® (semaglutide): in the common adverse reaction tables of section 6.1 and in the Medication Guide list of the most common side effects [1].
- Saxenda® (liraglutide): in the section 6.1 table, in the Medication Guide list of common side effects in adults, and again among post-marketing neurologic reports in section 6.2 [2].
- Foundayo™ (orforglipron): in the section 6.1 table and in the highlights list of the most common adverse reactions [3].
- Victoza® (liraglutide for type 2 diabetes): in the section 6.1 table of reactions reported in at least 5% of adults [8].
- Ozempic® and Rybelsus® (semaglutide for type 2 diabetes): not in the clinical trial tables; headache is listed under post-marketing experience in section 6.2 [4][5].
- Mounjaro® and Zepbound® (tirzepatide): headache is not listed in the adverse reaction tables or text of the current labels [6][7].
The numbers, compared with placebo
Section 6.1 tables only include reactions that were reported more often on the medicine than on placebo, and every number belongs to a specific pool of trials. Rates from different medicines’ trials cannot be compared directly.
| Label and trial pool | Placebo | Medicine |
|---|---|---|
| Wegovy®: three adult weight-reduction trials, up to 68 weeks [1] | 10% | 14% on 2.4 mg |
| Wegovy®: two 72-week trials of the 7.2 mg dose [1] | 7% | 8% on 2.4 mg, 9% on 7.2 mg |
| Wegovy®: adolescents aged 12 and older [1] | 16% | 17% |
| Saxenda®: adult weight management trials [2] | 12.6% | 13.6% |
| Foundayo™: two trials of up to 72 weeks [3] | 7% | 8% to 9% |
| Victoza®: adults with type 2 diabetes [8] | 7% | 10% to 11% |
Reading those numbers
Two things stand out. Headache was common on placebo too, so only part of the headaches reported on the medicine is likely to be linked to it. And the gap between the groups is small compared with nausea or vomiting in the same tables.
A missing entry is not proof that something never happens either. Labels list reactions that crossed a threshold in placebo-controlled trials and were more frequent than on placebo. The Zepbound® table uses a 2% threshold and headache is absent from it; the Mounjaro® table, from trials in type 2 diabetes, uses 5% [6][7].
Post-marketing lists, such as the ones in the Ozempic® and Rybelsus® labels, come from reports sent in voluntarily after approval. The labels say these reports come from a population of uncertain size, so neither their frequency nor a cause can be reliably established [4][5].
European and Canadian product information
European package leaflets group side effects by frequency: very common means more than 1 in 10 people, common up to 1 in 10. Headache is very common in the Wegovy® and Saxenda® leaflets and common in the Ozempic® and Victoza® leaflets [9][10][14][15].
The European Mounjaro® leaflet, which covers tirzepatide for both diabetes and weight management in the EU, does not list headache as a side effect of its own; it names headache only among the possible signs of low blood sugar [11]. Zepbound® has no separate European authorisation, since Mounjaro® is the EU name for tirzepatide. The Canadian Zepbound® product monograph, revised in June 2026, does not include headache in its adverse reaction table either [12].
Why it might happen
The labels do not name a cause for headache itself, so treat the second and third points as context rather than an explanation.
- What the labels support: the Ozempic®, Wegovy® and Saxenda® Medication Guides list headache among the signs of low blood sugar, with dizziness, sweating, shakiness, hunger, confusion and a fast heartbeat. The labels tie that risk mainly to use with insulin or a sulfonylurea [1][2][4].
- What the labels place around it: nausea, vomiting and diarrhea are the most common reactions in every GLP-1 label, and the labels warn that they can lead to fluid loss and dehydration. The Saxenda® label adds that fatigue and dizziness were mainly reported in the first 12 weeks, often together with stomach symptoms [1][2].
- What general sources describe: MedlinePlus lists lack of sleep, alcohol and caffeine withdrawal among migraine triggers, and suggests drinking water to avoid dehydration, especially after vomiting [13]. Changes in eating, drinking and sleep are common in the first weeks of a new medicine, but no label measures their part in headaches on these drugs.
Other common causes
MedlinePlus notes that serious causes of headache are rare. The most common type is tension headache, linked to tight muscles in the neck, shoulders, scalp and jaw, and to stress, anxiety, depression or posture. Migraine is usually one-sided and throbbing, often with nausea or sensitivity to light and sound [13].
Other everyday causes include colds, flu, fever, sinus swelling and premenstrual syndrome. MedlinePlus also describes rebound headaches, which can develop when pain medicines are used on more than three days a week [13]. A headache that started at the same time as a GLP-1 medicine may still have one of these causes.
What general guidance says helps
- MedlinePlus home measures for migraine or tension headache: drink water, especially if you have vomited, rest in a quiet dark room, put a cool cloth on your head and use relaxation techniques you know [13].
- Keep a headache diary: MedlinePlus suggests noting the day and time the pain began, what you ate and drank in the previous 24 hours, how you slept, what you were doing, how long it lasted and what made it stop [13].
- Pain relievers: MedlinePlus names acetaminophen, aspirin and ibuprofen for tension headaches and asks you to talk to your provider if you need them on three or more days a week [13]. No GLP-1 label names a pain reliever; they do note that delayed stomach emptying can affect how tablets are absorbed. The Canadian Zepbound® monograph says acetaminophen needs no dose adjustment with tirzepatide [1][12]. Ask your pharmacist which option, if any, suits you and your other medicines.
- If you have diabetes and use insulin or a sulfonylurea, the labels ask you to learn with your healthcare provider how to recognise and treat low blood sugar, so a headache with other low signs can be checked rather than guessed [4].
How a log helps
Headaches are easier to discuss when you can show a pattern rather than a feeling. Note when the headache started relative to your dose, how long it lasted, what you had eaten and drunk, how you slept, any caffeine or alcohol, what you took for it and any other symptoms on the same day.
Ozempic®, Wegovy®, Rybelsus®, Saxenda® and Victoza® are registered trademarks of Novo Nordisk A/S. Mounjaro® and Zepbound® are registered trademarks of Eli Lilly and Company, and Foundayo™ is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Novo Nordisk or Eli Lilly.
When to get help
| Sign | Who to contact | How fast | Source |
|---|---|---|---|
| A sudden, explosive or violent headache, or the worst headache you have ever had | Call 911 or your local emergency number, or go to the nearest emergency room | Emergency | MedlinePlus [13] |
| Headache with slurred speech, a change in vision, trouble moving your arms or legs, loss of balance, confusion or memory loss | Emergency care | Emergency | MedlinePlus [13] |
| Headache with fever, a stiff neck, nausea and vomiting, or after a head injury | Medical help right away | Emergency | MedlinePlus [13] |
| Trouble breathing or swallowing, fainting, or swelling that affects the face, lips, tongue or throat | Stop the medicine and get emergency help | Emergency | Medication Guides [1][2][4] |
| Headache with shakiness, sweating, confusion or hunger if you use insulin or a sulfonylurea | Follow your low blood sugar plan, then tell your prescriber | Today | Medication Guides [1][4] |
| A headache that gets worse over 24 hours, or nausea and vomiting that keep going | Your clinician or prescriber the same day | Today | MedlinePlus [13]; labels, fluid loss warning [1][6] |
| Headaches that keep coming back, or pain relievers needed on three or more days a week | Bring your diary to your next appointment | At your next appointment | MedlinePlus [13] |
