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GLP-1 fatigue: how common it is and what to check

Updated Sep 30, 2026. Numbers in brackets link to the source each fact comes from.

Tiredness is a listed side effect of the GLP-1 weight-loss medicines, but it is less common than stomach problems and the labels say little about why it happens or how long it lasts. On the Wegovy injection, 11% of people in the weight trials reported fatigue, against 5% on placebo [5]. Because tiredness has many causes, the more useful question is often what else could be behind it, such as dehydration, low blood pressure or low blood sugar.

How often it happened in the trials

Each label’s “fatigue” row groups several related terms. On Zepbound it covers asthenia (weakness), fatigue, lethargy and malaise [3]. On Wegovy it covers fatigue and asthenia [6]. The Zepbound medication guide words it for patients as “feeling tired” [13]. Column order comes from each label’s table header.

Medicine and trial group Placebo On the medicine
Zepbound 5, 10 and 15 mg, weight trials 3% 5%, 6%, 7% [1] [2]
Wegovy injection 2.4 mg, weight trials 5% 11% [4] [5]
Wegovy injection 7.2 mg trial (2.4 mg arm in brackets) 5% 11% (9%) [7] [8]
Foundayo 5.5, 9 and 17.2 mg, weight trials 4% 6%, 7%, 9% [9] [10]

The two diabetes medicines report it differently. The Ozempic label gives no exact figure; it lists fatigue among reactions seen in more than 0.4% of people [11]. Mounjaro’s diabetes trial table has no fatigue row, but in a separate heart outcomes trial of 6,647 adults with type 2 diabetes, fatigue was reported by 10% [12].

These trials enrolled different people, so the rows do not rank the drugs. See the full label tables for Zepbound, Wegovy, Foundayo, Ozempic and Mounjaro.

How long it lasts

None of the labels says. Unlike nausea, which the labels tie to the dose-raising period, there is no statement about fatigue getting better or worse over time. If it does not lift, treat it as something to look into rather than something to wait out.

Other causes the labels point to

  • Fluid loss. MedlinePlus says diarrhea can dehydrate you and leave you feeling weak [18]. The medication guides warn that nausea, vomiting and diarrhea can cause dehydration serious enough to affect the kidneys [19].
  • Low blood pressure. In the Zepbound weight trials, low blood pressure was reported by 1.6% of people on the drug and 0.1% on placebo, more often in people also taking blood pressure medicine, and sometimes along with stomach symptoms and dehydration [14]. Dizziness was reported by 4% to 5% on Zepbound and 2% on placebo [15].
  • Low blood sugar. The risk is higher if you also take insulin or a sulfonylurea [16]. Its signs can include weakness, shakiness, sweating and confusion [17].
  • Everything else. MedlinePlus lists many causes of fatigue unrelated to these drugs, including anemia, depression, sleep disorders, pain and thyroid problems [20].

How much you eat can matter too, according to a 2025 joint advisory from four obesity and nutrition groups (the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society). It says studies of people taking GLP-1s for obesity observed calorie intake falling by 16% to 39% [26]. A cut that large and fast can leave people short of vitamins and minerals, especially below about 1,200 calories a day for women and 1,800 for men [27]. Among the signs of a real deficiency, the advisory lists fatigue beyond what would be expected, along with heavy hair loss and muscle weakness [28]. If you are eating far less than before and feel worn out, that is worth raising with your prescriber.

What helps, according to MedlinePlus

This is general advice for fatigue, not advice written for GLP-1 medicines.

  • Get enough sleep, eat a balanced diet, drink water through the day, and exercise regularly [22].
  • Do not lean on caffeine: MedlinePlus says stimulants are not an effective treatment for fatigue [23].
  • Do not stop or change any medicine without first talking to your provider [24].

When to call a doctor

MedlinePlus says fatigue that does not improve with enough sleep, good nutrition and less stress should be checked by a provider [21]. It says to contact your provider right away for confusion or dizziness, blurred vision, or little or no urine [25]. Very little urine can also be a sign of dehydration, which the GLP-1 medication guides ask you to report right away when stomach symptoms do not go away [19].

Sources

  1. Adverse Reaction Placebo (N=958) % ZEPBOUND 5 mg (N=630) % ZEPBOUND 10 mg (N=948) % ZEPBOUND 15 mg (N=941) % dailymed.nlm.nih.gov, read Sep 27, 2026.
  2. Fatiguee 3 5 6 7 dailymed.nlm.nih.gov, read Sep 27, 2026.
  3. e Includes asthenia, fatigue, lethargy, malaise. dailymed.nlm.nih.gov, read Sep 27, 2026.
  4. Placebo N=1,261 % WEGOVY Injection (2.4 mg Once Weekly) N=2,116 % dailymed.nlm.nih.gov, read Sep 27, 2026.
  5. Fatigueb 5 11 dailymed.nlm.nih.gov, read Sep 27, 2026.
  6. b Includes fatigue and asthenia. dailymed.nlm.nih.gov, read Sep 27, 2026.
  7. Placebo N=303 % WEGOVY Injection (2.4 mg Once Weekly) N=304 % WEGOVY Injection (7.2 mg Once Weekly) N=1,311 % dailymed.nlm.nih.gov, read Sep 27, 2026.
  8. Fatiguec 5 9 11 dailymed.nlm.nih.gov, read Sep 27, 2026.
  9. Adverse Reaction Placebo (N=1,576) % FOUNDAYO 5.5 mg once daily (N=1,051) % FOUNDAYO 9 mg once daily (N=1,055) % FOUNDAYO 17.2 mg once daily (N=1,049) % dailymed.nlm.nih.gov, read Sep 27, 2026.
  10. Fatiguea 4 6 7 9 dailymed.nlm.nih.gov, read Sep 27, 2026.
  11. Other adverse reactions with a frequency of >0.4% were associated with OZEMPIC include fatigue, dysgeusia and dizziness. dailymed.nlm.nih.gov, read Sep 27, 2026.
  12. In a CV outcomes trial of 6,647 adults with type 2 diabetes mellitus and established CV disease exposed to MOUNJARO, adverse reactions reported with MOUNJARO were similar with the exception of dysesthesia (0.7%), decreased appetite (17%), constipation (13%), vomiting (12%), abdominal pain (10%), and fatigue (10%) dailymed.nlm.nih.gov, read Sep 27, 2026.
  13. The most common side effects of ZEPBOUND include: nausea diarrhea vomiting constipation stomach (abdominal) pain indigestion injection site reactions feeling tired allergic reactions belching hair loss heartburn dailymed.nlm.nih.gov, read Sep 27, 2026.
  14. In a pool of Study 1 and 2, hypotension occurred more frequently among patients taking ZEPBOUND (1.6%) than patients taking placebo (0.1%). Hypotension was more frequently seen in ZEPBOUND-treated patients on concomitant antihypertensive therapy (2.2%) compared to ZEPBOUND-treated patients not on antihypertensive therapy (1.2%). Hypotension also occurred in association with gastrointestinal adverse events and dehydration. dailymed.nlm.nih.gov, read Sep 27, 2026.
  15. Dizziness 2 4 5 4 dailymed.nlm.nih.gov, read Sep 27, 2026.
  16. Your risk for getting low blood sugar may be higher if you use ZEPBOUND with medicines that can cause low blood sugar, such as an insulin or sulfonylurea. dailymed.nlm.nih.gov, read Sep 27, 2026.
  17. Signs and symptoms of low blood sugar may include: dizziness or light-headedness sweating confusion or drowsiness headache blurred vision slurred speech shakiness fast heartbeat anxiety, irritability, or mood changes hunger weakness feeling jittery dailymed.nlm.nih.gov, read Sep 27, 2026.
  18. It can make you lose too much fluid (dehydrated) and feel weak. medlineplus.gov, read Sep 27, 2026.
  19. Diarrhea, nausea, and vomiting may cause a loss of fluids (dehydration) which may cause kidney problems. It is important for you to drink fluids to help reduce your chance of dehydration. Tell your healthcare provider right away if you have nausea, vomiting, or diarrhea that does not go away. dailymed.nlm.nih.gov, read Sep 27, 2026.
  20. Anemia (including iron deficiency anemia ) Depression or grief Iron deficiency (without anemia) Medicines, such as sedatives or antidepressants Persistent pain Sleep disorders such as insomnia , obstructive sleep apnea , or narcolepsy Thyroid gland that is underactive or overactive medlineplus.gov, read Sep 27, 2026.
  21. When fatigue is not relieved by enough sleep, good nutrition, or a low-stress environment, it should be evaluated by your health care provider. medlineplus.gov, read Sep 27, 2026.
  22. Get enough sleep each night. Make sure your diet is healthy and well-balanced, and drink plenty of water throughout the day. Exercise regularly . medlineplus.gov, read Sep 27, 2026.
  23. Stimulants (including caffeine) are not effective treatments for fatigue. medlineplus.gov, read Sep 27, 2026.
  24. DO NOT stop or change any medicines without first talking to your provider. medlineplus.gov, read Sep 27, 2026.
  25. Contact your provider right away if you have any of the following: Confusion or dizziness Blurred vision Little or no urine output medlineplus.gov, read Sep 27, 2026.
  26. Individuals using GLP-1s to treat obesity experience significant reductions in appetite and energy intake, with observed caloric reductions of 16%–39% pmc.ncbi.nlm.nih.gov, read Sep 28, 2026.
  27. This large, rapid reduction can lead to insufficient intakes of essential vitamins and minerals, especially at energy intakes <1200 kcal/d for females and <1800 kcal/d for males pmc.ncbi.nlm.nih.gov, read Sep 28, 2026.
  28. Signs of frank nutrient deficiency include fatigue beyond expected levels, excessive hair loss, skin flakiness or itching, muscle weakness, poor wound healing, and unusual bruising pmc.ncbi.nlm.nih.gov, read Sep 28, 2026.

This page reports what official sources say; it is not medical advice. Medical disclaimer.