- Yes, for some people: in the trials behind the US labels, 11% of adults on Wegovy 2.4 mg reported fatigue vs 5% on placebo, and 5–7% on Zepbound vs 3%.1
- Headache (14% vs 10%) and dizziness (8% vs 4%) were also more common on Wegovy. On Zepbound, dizziness was 4–5% vs 2%.1
- The labels and a 2025 nutrition advisory point to possible contributors: eating much less, fluid loss from stomach side effects, low blood pressure and, in people with diabetes, low blood sugar.1,2
Does Wegovy or Zepbound make you tired? The trial numbers
Each US label has a table of side effects that were more common on the drug than on placebo in its main trials. For Wegovy (semaglutide), the table pools the STEP 1, 2 and 3 trials: 2,116 adults with overweight or obesity on 2.4 mg weekly and 1,261 on placebo, over 68 weeks. For Zepbound (tirzepatide), it pools SURMOUNT-1 and SURMOUNT-2: adults with obesity or overweight, with or without type 2 diabetes, over 72 weeks.1
| Side effect | Wegovy 2.4 mg | Placebo | Zepbound 5 / 10 / 15 mg | Placebo |
|---|---|---|---|---|
| Fatigue* | 11% | 5% | 5% / 6% / 7% | 3% |
| Headache | 14% | 10% | not listed | |
| Dizziness | 8% | 4% | 4% / 5% / 4% | 2% |
| Low blood pressure | 1.3% | 0.4% | 1.6% (pooled doses) | 0.1% |
Note the placebo rates. Some tiredness and headache happen anyway during a long trial. The extra share caused by the medicine is the gap: about 6 percentage points for fatigue on Wegovy and 2 to 4 points on Zepbound.
The newer Wegovy 7.2 mg dose shows a similar picture. In its trials, fatigue was reported by 11% on 7.2 mg, 9% on 2.4 mg and 5% on placebo; headache by 9%, 8% and 7%; and dizziness by 6%, 5% and 1%.1
What about Ozempic and Mounjaro?
At the lower doses used for type 2 diabetes, fatigue is less prominent in the labels. The Ozempic label lists fatigue and dizziness among side effects seen in more than 0.4% of patients, and headache among reports after approval. In Mounjaro's heart outcomes trial of 6,647 adults with type 2 diabetes and heart disease, 10% reported fatigue.1
Why might a GLP-1 make you tired?
The labels and trials do not establish one cause. These are the contributors that official labels and peer-reviewed guidance describe:
- Eating much less. The 2025 joint advisory from four US nutrition and obesity societies reports observed calorie reductions of 16% to 39% on GLP-1 medicines. It warns that such a large, rapid drop can lead to low intake of vitamins and minerals, especially below about 1,200 calories a day for women and 1,800 for men, and lists fatigue beyond expected levels among signs of a frank nutrient deficiency.2
- Fluid loss. Both labels warn that nausea, vomiting and diarrhea can cause dehydration, and instruct patients to take precautions to avoid fluid depletion. The advisory adds that dehydration can cause heart palpitations as well as kidney injury.1,2 A 2022 expert consensus notes that people often drink less because they feel full.4
- Low blood pressure. The labels say low blood pressure was more common on the drug, was sometimes linked to stomach side effects and fluid loss, and was seen more often in people also taking blood pressure medicines (on Zepbound, 2.2% vs 1.2% without them). On Wegovy, fainting was reported by 0.8% vs 0.2% on placebo.1
- Low blood sugar, mainly with diabetes medicines. In SURMOUNT-2, adults with type 2 diabetes, low blood sugar (under 54 mg/dL) occurred in 4.2% on Zepbound vs 1.3% on placebo, and in 10.3% of those also on a sulfonylurea vs 2.1% of those not. In the Wegovy trial of adults with type 2 diabetes not on insulin, it was 6% vs 2%. The labels say risk rises when these drugs are used with insulin or a sulfonylurea.1
The Medication Guides list dizziness or light-headedness, headache, weakness, shakiness, sweating, confusion or drowsiness among possible signs of low blood sugar.1 The Wegovy label notes that hypoglycemia was not systematically captured in its weight trials of people without diabetes, though episodes have been reported with GLP-1 medicines in that group.1
How long does GLP-1 fatigue last?
We could not find a published analysis that tracks how long fatigue, headache or dizziness lasts on Wegovy or Zepbound, so we cannot give a number. What is documented is the timing of stomach side effects, which can drive eating and drinking less. In the STEP 1–3 trials, nausea, diarrhea and vomiting peaked around week 20 and then declined.3 The Zepbound label says most nausea, vomiting and diarrhea happened during dose escalation and decreased over time.1 If your tiredness tracks those symptoms, it may follow the same pattern, but that has not been measured directly.
What guidance suggests
The 2025 advisory focuses on getting enough nutrition while appetite is low: prioritizing protein, a diversity of nutrient-dense, minimally processed foods, and regular reassessment of diet and hydration, with lab checks for deficiencies where clinically appropriate.2 For practical meal ideas, see what to eat on a GLP-1. If fewer fluids are also leaving you constipated, see GLP-1 constipation. For nausea, see how common nausea is on a GLP-1.
If you take insulin or a sulfonylurea, the labels say your clinician may need to lower those doses when you start a GLP-1. That is a decision for your care team, not something to change on your own.1
When to get checked
Mild tiredness during dose increases is common. Some symptoms need prompt attention:
- Signs of low blood sugar such as shakiness, sweating, confusion or a fast heartbeat, especially if you also take insulin or a sulfonylurea. The labels instruct patients to report these to their provider.1
- Nausea, vomiting or diarrhea that will not go away. The labels tell patients to contact their provider right away because dehydration can lead to kidney problems.1
- Fainting or dizziness on standing, particularly if you take blood pressure medicines.
- Fatigue that is severe, lasts weeks or keeps getting worse. It can have causes unrelated to the medicine, such as anemia, thyroid problems or poor sleep, which only a clinician can sort out.
Common questions
Does Wegovy make you tired?
It can. In the STEP 1 to 3 trials summarized in the Wegovy label, 11% of adults with overweight or obesity on semaglutide 2.4 mg reported fatigue or weakness, compared with 5% on placebo. Most people in the trials did not report it.
Does Zepbound make you tired?
Some people report it. In the pooled SURMOUNT-1 and SURMOUNT-2 weight trials summarized in the Zepbound label, fatigue, weakness, lethargy or malaise was reported by 5%, 6% and 7% of adults on tirzepatide 5, 10 and 15 mg, compared with 3% on placebo.
How long does Wegovy fatigue last?
No published trial analysis we found reports how long fatigue lasts on Wegovy or Zepbound. The labels and trial analyses say stomach side effects, which can lead to eating and drinking less, happen mostly during dose increases and ease over time. Tiredness that lasts or gets worse is worth raising with your clinician.
Can GLP-1 medicines cause headaches?
Headache was reported by 14% of adults on semaglutide 2.4 mg in the STEP 1 to 3 trials, compared with 10% on placebo, according to the Wegovy label. Headache does not appear in the Zepbound label's table of common side effects from its main weight trials.
Can Wegovy or Zepbound make you dizzy?
Dizziness was reported by 8% of adults on Wegovy 2.4 mg vs 4% on placebo, and by 4% to 5% on Zepbound vs 2% on placebo, in the trials behind each US label. Both labels also report low blood pressure, sometimes linked to fluid loss from stomach side effects.
Sources
- US prescribing information and Medication Guides: WEGOVY, ZEPBOUND, OZEMPIC and MOUNJARO (DailyMed; 2026 versions checked November 2026). Sections 5, 6.1, 6.2 and Medication Guide.
- Mozaffarian D, Agarwal M, Aggarwal M, et al. Nutritional priorities to support GLP-1 therapy for obesity: A joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Obesity (Silver Spring). 2025;33(8):1475-1503. doi:10.1002/oby.24336 · Full text (PMC)
- Wharton S, Calanna S, Davies M, et al. Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg in adults with overweight or obesity, and the relationship between gastrointestinal adverse events and weight loss. Diabetes Obes Metab. 2022;24(1):94-105. doi:10.1111/dom.14551 · Full text (PMC)
- Gorgojo-Martínez JJ, Mezquita-Raya P, Carretero-Gómez J, et al. Clinical Recommendations to Manage Gastrointestinal Adverse Events in Patients Treated with Glp-1 Receptor Agonists: A Multidisciplinary Expert Consensus. J Clin Med. 2022;12(1):145. doi:10.3390/jcm12010145 · Full text (PMC)
