In short
Wegovy and Zepbound list fatigue, in up to 11% and 7% of people, against 5% and 3% on placebo. We found no source on when it starts or how long it lasts. The sources give no advice specific to fatigue, though eating very little is a known concern. Fatigue beyond what you would expect is worth raising with your prescriber.
How common it is
| Label | Fatigue | On placebo |
|---|---|---|
| Wegovy (2.4 mg) | 11% | 5% |
| Zepbound (5, 10, 15 mg) | 5%, 6%, 7% | 3% |
The Mounjaro label reports fatigue in 10% of people in its cardiovascular trial, which had no placebo group. The Ozempic label gives no exact figure.
What we could not find
The labels and expert papers we read do not say when fatigue tends to start or how long it lasts, and they give no steps aimed at it directly. We would rather say so than guess.
Things worth checking with your prescriber
- How much you are eating. People on these medicines eat 16% to 39% less. A joint advisory lists fatigue beyond expected levels among signs of nutrient deficiency, in the context of large calorie reductions.
- Fluids. If you are also vomiting or have diarrhea, fatigue with dizziness or confusion needs attention.
- Low blood sugar. The Medication Guides list weakness and drowsiness among its signs. The risk is higher with insulin or a sulfonylurea.
When to get help
The labels and Medication Guides name these. This is not the full list, so read the guide that came with your medicine.
- Severe stomach-area pain that will not go away, sometimes reaching your back, with or without vomiting. The guides say to stop the medicine and call your healthcare provider right away. It can be a sign of pancreatitis.
- Upper stomach pain, fever, yellow skin or eyes, or clay-colored stools. Call your provider. These can be gallbladder problems.
- Vomiting or diarrhea that does not go away. Tell your provider right away. The labels warn that fluid loss can lead to kidney injury, sometimes serious.
- Signs of a serious allergic reaction. Stop the medicine and get medical help right away.
If something is severe, sudden or frightening, get medical help. Do not wait to log it.
Food and strength can matter here: see what to eat on a GLP-1 and muscle loss and protein. If stomach problems are also part of it, start with nausea and vomiting or the side effects guide.
What this means in practice
Fatigue is real enough to appear on two labels, but nobody has mapped it out the way they have nausea. If you are tired, the useful questions are what you are eating, whether you are drinking enough, and whether anything else has changed. Bring dates and notes to your prescriber, because a pattern is easier to act on than a general feeling.
How Reko helps
Log tiredness alongside sleep, food and doses. Reko keeps your symptoms beside your doses, so you can show your prescriber when something began and how it changed. It does not tell you what a symptom means, and it never suggests a dose.
Questions people ask
Is fatigue a side effect of GLP-1 medicines?
It is listed on the Wegovy and Zepbound labels, more often than on placebo. The Mounjaro label reports it in its cardiovascular trial, and the Ozempic label gives no exact figure.
How long does GLP-1 fatigue last?
We found no source that says. The labels and expert papers we read do not describe when it starts or how long it lasts.
Could I be tired because I am not eating enough?
Possibly. A joint advisory reports people eat 16% to 39% less, and lists fatigue beyond expected levels among signs of nutrient deficiency. Raise it with your prescriber.
Could fatigue be low blood sugar?
The Medication Guides list weakness and drowsiness among signs of low blood sugar. The risk is higher if you also take insulin or a sulfonylurea, so tell your provider.
Is fatigue a reason to stop?
That is a decision for you and your prescriber. The Medication Guides ask you to talk to your provider about side effects that bother you or do not go away.
Reko records what you and your prescriber decide. This guide is general information and not medical advice.
Read next
Recipes to try
These are ordinary recipes and do not treat any side effect.
Useful tools
- Mounjaro prescribing information on DailyMed. Checked 2 November 2026.
- Zepbound prescribing information on DailyMed. Checked 2 November 2026.
- Ozempic prescribing information on DailyMed. Checked 2 November 2026.
- Wegovy prescribing information on DailyMed. Checked 2 November 2026.
- Mozaffarian D et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory. Am J Clin Nutr 2025;122(1):344-367. Mostly expert opinion.
- Gorgojo-Martínez JJ et al. Clinical recommendations to manage gastrointestinal adverse events in patients treated with GLP-1 receptor agonists: a multidisciplinary expert consensus. J Clin Med 12(1):145. An expert consensus, not a trial.