Does Ozempic or Mounjaro make you tired?

Feeling wiped out after starting Ozempic, Wegovy or Mounjaro is one of the most common complaints people report, and it is easy to blame the drug. Tiredness has many possible sources, though, and the 2026 evidence splits into two directions worth separating: a small, direct signal, and a set of everyday causes you can usually check and fix.

The short version is that these drugs appear to nudge daytime sleepiness up by a small amount, while at the same time strongly improving sleep apnea, which is itself a major cause of exhaustion. So there is no single answer to "does Ozempic make you tired." The most useful move is to separate the drug's tiny direct effect from the common causes of fatigue that come with eating far less.

Does Ozempic make you sleepy?

A large 2026 study found GLP-1 drugs were linked to a small increase in daytime sleepiness, but the effect was minor. Researchers used the TriNetX network to compare 118,993 GLP-1 users against 118,993 matched non-users, all adults aged 18 to 50 with type 2 diabetes or obesity who had undergone a sleep study.1

People taking a GLP-1 drug had a modestly higher risk of new hypersomnolence, the medical term for excessive daytime sleepiness, at both 1 year (hazard ratio 1.21) and 5 years (hazard ratio 1.23).1 Two details keep this in perspective. The absolute increase was tiny: about 0.4% more people at 1 year and 0.7% more at 5 years.1 And the same study found no significant rise in disturbed sleep, restless legs syndrome, parasomnia or narcolepsy, so the signal is specific to daytime sleepiness rather than broken sleep across the board.1

Can these drugs improve sleep apnea?

Yes, and this is the side of the story that pulls toward more energy, not less. Obstructive sleep apnea, where the airway repeatedly collapses during sleep, is one of the biggest drivers of daytime sleepiness, and it affects a large share of people with obesity.2 A 2026 review in JAMA Otolaryngology-Head and Neck Surgery pooled six meta-analyses showing GLP-1 drugs lowered the apnea-hypopnea index, a count of breathing interruptions per hour, by 5.7 to 21.9 events an hour.2

The strongest evidence comes from the SURMOUNT-OSA phase 3 trials, run by Eli Lilly, in which tirzepatide cut the apnea-hypopnea index by 20 to 24 events an hour compared with placebo and put 42% to 50% of patients into disease remission.2 On the strength of those results, tirzepatide, sold as Zepbound, became the first drug approved for moderate-to-severe sleep apnea in adults with obesity in December 2024.2

The benefit has limits worth naming. The same review notes GLP-1 drugs did not match CPAP, the mask-based standard treatment, which reduces breathing interruptions more (roughly 31 versus 22 events an hour), and the gains come mainly from weight loss, so they fade if the weight returns.2 Even so, for someone with untreated sleep apnea, a GLP-1 drug may leave them less sleepy over time, not more.

Why am I so tired on Ozempic?

Most fatigue on a GLP-1 drug is not a mystery and traces to a handful of common, checkable causes. When appetite drops sharply, it is easy to eat too little overall, take in too little protein, or become mildly dehydrated from nausea, vomiting or diarrhea, and each of those can leave you flat. These are general effects of eating far less, not findings of the sleepiness study.

Low iron is a different case: it is a classic, treatable cause of tiredness, and the 2026 cohort did find a small but real rise in iron deficiency among GLP-1 users over 5 years.1 In people who also take insulin or a sulfonylurea, low blood sugar can feel like sudden exhaustion too. The table above sets out these causes and why each one saps energy.

Two of these are worth acting on early. Eating enough protein protects against the muscle loss that comes with rapid weight change, covered in our guides to whether high-protein diets can slow GLP-1 muscle loss and how much muscle you lose on a GLP-1. If tiredness is persistent, a simple blood test for iron and blood sugar is a reasonable first step to raise with your doctor.

The drug seems to add a little sleepiness, and take away a lot from sleep apnea. For most people, the bigger lever is the everyday causes of tiredness that come with eating far less.

When should tiredness be checked?

New, severe or lasting daytime sleepiness deserves a medical review rather than self-diagnosis from an article. That is especially true if the sleepiness comes with loud snoring or witnessed pauses in breathing at night, which point to untreated sleep apnea, or with dizziness, a very low appetite or signs of low blood sugar. A doctor can check simple, fixable causes like iron and blood sugar, and decide whether a sleep study is needed.

None of this is a reason to start, stop or change a dose on your own. There is no randomized trial testing GLP-1 drugs for fatigue, so the evidence here shows an association, not proof, and the sleepiness study looked only at adults aged 18 to 50 who had already had a sleep study, a specific group rather than every user. Any change to treatment belongs with the doctor who prescribed it.

In one sentence: there is a small, observational signal that GLP-1 drugs like Ozempic and Mounjaro can nudge daytime sleepiness up, set against stronger evidence that they ease sleep apnea, and most fatigue on these drugs traces to fixable causes such as low iron, too little food and dehydration.12