# Do GLP-1 Drugs Make You Tired? Daytime Sleepiness Improved by 0.20 Points Do GLP-1 drugs make you tired? No trial measured fatigue | daytime sleepiness improved 0.20 Epworth points, while ferritin ran 26% to 30% below a comparison group. Publisher: This GLP Editorial Team Canonical: https://thisglp.com/research/do-glp1-drugs-make-you-tired Updated: 2026-09-18 Published: 2026-09-17 [← Research](https://thisglp.com/research) Safety # Do GLP-1 Drugs Make You Tired? Daytime Sleepiness Improved by 0.20 Points No randomized trial of this drug class reported fatigue as an endpoint, and the nearest measured proxy moved a tenth of the distance a person can feel. The mechanisms that would explain feeling tired were measured, but never as tiredness. [This GLP Editorial Team](https://thisglp.com/about)September 20269 min read Daytime sleepiness, Epworth points improved · measured effect · 0.20 points · noticeable · 2 points · 95% CI 0.14 to 0.26 — precisely measured, and invisible · Breathing events fell 15.28 an hour in the same analysis. **Research, not medical advice.** This GLP is independent and educational. Nothing here is a substitute for individualized care from a licensed clinician, and reading it creates no doctor–patient relationship. Talk to your own provider before starting, stopping, or changing any medication, peptide, or therapy. See our [methodology](https://thisglp.com/methodology) and [terms](https://thisglp.com/terms). No trial of this drug class has measured fatigue as an endpoint, so the honest answer is assembled from adjacent measurements rather than read off a result. The closest direct one is daytime sleepiness, pooled across fifteen studies and 1,877 participants with sleep apnea, where the Epworth score improved by 0.20 points with a 95% confidence interval from 0.14 to 0.26 [\[1\]](https://thisglp.com/research/do-glp1-drugs-make-you-tired#ref-1). Two points is the smallest change on that scale anybody notices, so the measured effect is a tenth of the threshold of perception, and it runs toward less sleepiness rather than more. What the same literature does show is depletion: ferritin 26% to 30% below a comparison group on a different diabetes drug, and more than 60% of users eating below the estimated requirement for iron [\[2\]](https://thisglp.com/research/do-glp1-drugs-make-you-tired#ref-2). ## Key takeaways - No randomized trial of a GLP-1 drug has reported fatigue, tiredness or energy as a named endpoint. - Daytime sleepiness, the nearest measured proxy, improved by 0.20 Epworth points (95% CI 0.14 to 0.26) against a 2-point threshold for a noticeable change. - Ferritin ran 26% to 30% lower than in a comparison group on a different diabetes drug, and over 60% of users ate below the estimated iron requirement. - Resting energy expenditure fell further than body composition alone predicts — in the treated group and in the lifestyle-only group equally. - Skeletal muscle mass fell from 29.9 kg to 28.7 kg over twelve months while handgrip strength was preserved. Tiredness is one of the commonest things people report on these drugs and one of the least studied, which is an uncomfortable combination. The trials count nausea, vomiting, diarrhea and constipation, and the time course of those is set out in [the nausea timeline](https://thisglp.com/research/how-long-does-nausea-last-on-a-glp1). Energy was not on the list. ## The one scale that touches it The Epworth Sleepiness Scale asks how likely someone is to doze off in eight ordinary situations, and it is the only instrument in this literature that measures anything close to how tired a person feels. A network meta-analysis of fifteen studies and 1,877 participants with moderate to severe obstructive sleep apnea pooled it, and GLP-1 drugs improved the score by 0.20 points against placebo [\[1\]](https://thisglp.com/research/do-glp1-drugs-make-you-tired#ref-1). In the same analysis, breathing events fell by 15.28 an hour, 95% CI 8.35 to 22.22, which is a large effect on the thing a machine counts. Significant, and a tenth of noticeable The minimal clinically important difference on the Epworth scale is two points — the smallest change patients said they had to feel before they would call it better. A measured improvement of 0.20 points is a tenth of that, and the interval is tight enough to say the true effect is also about a tenth of it. The authors say so themselves, in the abstract. Significance answers whether an effect exists; a minimal clinically important difference answers whether anybody could tell. The subgroup analyses behind the sleep apnea approval point the same way. Reductions in the apnea-hypopnea index appeared in every subgroup examined — by age from 27.7 to 34.1 events per hour, by body mass index from 25.2 to 34.4, by neck circumference from 23.9 to 30.8 [\[3\]](https://thisglp.com/research/do-glp1-drugs-make-you-tired#ref-3). Those analyses are descriptive, with no interaction tests and no subgroup confidence intervals reported, and the full reading is in [the subgroup post hoc](https://thisglp.com/research/apnea-improved-across-every-subgroup). For somebody whose tiredness comes from untreated apnea, this is the mechanism by which a GLP-1 would make them less tired rather than more. ## The mechanisms that would push the other way Three findings in this literature are consistent with feeling worse rather than better, and none of them was collected as a fatigue measurement. The first is iron. A narrative review covering six studies and 480,825 adults found ferritin running 26% to 30% below a comparison group taking an SGLT2 inhibitor, and more than 60% of users eating below the estimated requirement for iron and for calcium [\[2\]](https://thisglp.com/research/do-glp1-drugs-make-you-tired#ref-2). Low iron stores are among the most ordinary causes of tiredness there is, and the full nutritional picture is in [the micronutrient evidence](https://thisglp.com/research/do-you-need-vitamins-on-a-glp1). The second is thiamine, at the severe end of the same mechanism, where prolonged vomiting and rapid weight loss have preceded every published case of Wernicke’s encephalopathy in this setting. Fatigue and confusion are early features, and the staging of it is in [the thiamine cases](https://thisglp.com/research/can-a-glp1-cause-thiamine-deficiency). Six published cases cannot produce a rate, and nothing here says this is common. The third is energy expenditure itself. In 83 adults followed for twelve months at one obesity unit, skeletal muscle mass fell from 29.9 kg to 28.7 kg and fat-free mass from 53.8 kg to 52.7 kg, both at p < 0.001 [\[4\]](https://thisglp.com/research/do-glp1-drugs-make-you-tired#ref-4). Handgrip strength was preserved, in the treated group and in the lifestyle-only group alike. Resting energy expenditure fell further than the change in body composition predicts, and it did so equally in both groups, which makes it a feature of losing weight rather than of the drug. ## What to do with an answer this thin Someone who feels tired on one of these drugs is not contradicted by the evidence, because the evidence never asked. The measurable causes worth ruling out are the ones a blood test settles: iron and ferritin, vitamin B12, vitamin D, and thyroid function. A reader losing lean mass quickly has a second, separate question to ask, and it is laid out in [the muscle-loss evidence](https://thisglp.com/research/do-you-lose-muscle-on-a-glp1). The one thing this page will not do is convert an absence of data into a reassurance. A drug that reduces food intake by roughly 271 calories at a measured meal is reducing the intake of everything, as [the intake measurements](https://thisglp.com/research/how-much-less-do-you-eat-on-a-glp1) show. The trials that would have detected a fatigue signal were not designed to collect one. ## Frequently asked Do GLP-1 drugs make you tired? No randomized trial reported fatigue as an endpoint. The nearest measured proxy, daytime sleepiness, improved by 0.20 Epworth points against a 2-point threshold for a change a person can notice. What would explain feeling tired on one? Iron depletion is the most ordinary candidate: ferritin ran 26% to 30% lower than in a comparison group, and over 60% of users ate below the estimated iron requirement. Lost lean mass and a fall in resting energy expenditure are the others. Does a GLP-1 improve daytime sleepiness? Slightly, and by less than anyone can feel. The pooled improvement was 0.20 Epworth points, 95% CI 0.14 to 0.26, where two points is the smallest noticeable change. What should be checked? The measurable causes a blood test settles — iron and ferritin, vitamin B12, vitamin D and thyroid function. Prolonged vomiting with rapid weight loss is the pattern that preceded every published thiamine case. ## Sources 1. \[1\] Zheng J, et al. (2026). Efficacy of SGLT2 inhibitors, GLP-1 receptor agonists, and aerobic exercise for moderate-to-severe obstructive sleep apnea in overweight or obese patients: a network meta-analysis Frontiers in Endocrinology. [PMID 42676363](https://pubmed.ncbi.nlm.nih.gov/42676363/) 2. \[2\] Urbina J, et al. (2026). Micronutrient and Nutritional Deficiencies Associated With GLP-1 Receptor Agonist Therapy: A Narrative Review Clinical Obesity. [PMID 41549912](https://pubmed.ncbi.nlm.nih.gov/41549912/) 3. \[3\] Falcon B, Xie CC, Redline S, Grunstein R, et al. (2026). Association of tirzepatide with changes in OSA-related measures based on baseline characteristics - post hoc analyses of SURMOUNT-OSA Journal of Clinical Sleep Medicine. [PMID 42675225](https://pubmed.ncbi.nlm.nih.gov/42675225/) 4. \[4\] Filippi-Arriaga F, et al. (2026). Longitudinal Changes in Body Composition, Adaptive Thermogenesis and Muscle Strength in Patients with Obesity Treated with Semaglutide Obesity Facts. [PMID 42640861](https://pubmed.ncbi.nlm.nih.gov/42640861/) ## More in Safety - [ Medication list · Check combinations · Fluid loss · Changes kidney risk · Pharmacist · Choose a safe option ### Can You Take Ibuprofen With Ozempic? Check Kidney and Stomach Risks ](https://thisglp.com/research/can-you-take-ibuprofen-with-ozempic) - [ 1.9% · Placebo · 8.5% · Ozempic 0.5 mg · 8.8% · Ozempic 1 mg ### Does Ozempic Cause Diarrhea? Rates, Timing, and When to Call ](https://thisglp.com/research/does-ozempic-cause-diarrhea) - [ Sit down · Prevent a fall · Check context · Glucose and fluids · Get help · Severe symptoms ### Does Ozempic Cause Dizziness? What to Check First ](https://thisglp.com/research/does-ozempic-cause-dizziness)