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Symptom question · incretin class

Does Mounjaro cause fatigue?

Yes. 4 of the 36 compounds here list fatigue as a reported side effect. The rate differs by drug and study. The table below gives each source’s figure.

Source: checked against 36 compound guides; rates are shown exactly as reportedFDA label

Being listed means fatigue was reported during the trials behind the label. It does not prove what caused one person’s tiredness, how long it will last, or how much may come from other changes happening at the same time.

Mounjaro is a brand name for tirzepatide, the same medicine sold as Zepbound for a different approved use. The reaction and its rate on this page come from the tirzepatide label cited in the table. The profile belongs to the drug rather than to the brand.

Medically reviewed by Jennifer Montecillo, MD · non-practicing medical reviewer

Information checked 2026-08-20

At a glance

Compounds that list it

5 of 36

Only in a combined category

1

No published human safety data

11

Best available source

FDA label

Which compounds list fatigue

Fatigue appears in the FDA labels for two compounds. Most early trial reports do not mention it. That difference may reflect how the documents report side effects, so it should not be used to rank the compounds.

◆ Fatigue across 36 compoundssource shown for every row
Every compound covered on this site, showing whether it lists fatigue and at what frequency its own cited source states.
CompoundHow it appearsFrequency reportedSource type
TirzepatideZepbound, MounjaroFatigueCommon (1–10%)FDA label
SemaglutideWegovy, Ozempic, RybelsusFatigueCommon (1–10%)FDA label
LiraglutideVictoza, SaxendaNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—FDA label
RetatrutideNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—Human trial
CagrilintideNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—Human trial
SurvodutideNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—Human trial
BPC-157No published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
TesamorelinEgrifta SV, Egrifta WRNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—FDA label
PT-141VyleesiFatigue3.2% vs 0.5% on placeboFDA label
CJC-1295Not listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
IpamorelinNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—Human trial
TB-500No published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
GHK-CuNo published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
SermorelinNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
MOTS-cNo published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
AOD-9604FatigueReported in human safety work that reaches this page only through a review — no rate is publishedlimited human data
NAD+Not listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
EpitalonNo published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
Kisspeptin-10No published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
DSIPNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
HexarelinNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
IGF-1 LR3No published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
PEG-MGFNo published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
LL-37Not listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
KPVNo published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
Thymosin alpha-1Not listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
SS-31ForzinityNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—FDA label
SemaxNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
SelankNo published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
Melanotan IIDrowsiness and tirednesscounted inside a grouped figure, not on its ownGraded moderate in one of the two subjects who reached 0.03 mg/kg — the finding that set the trial’s recommended dose one step lowerlimited human data
MazdutideNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—Human trial
PinealonNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—limited human data
AHK-CuNo published human safety dataNo human trial has published enough safety data to list reactions for this compound.—no human dose shown to work
VK2735Not listed in the source checkedThe label or study checked for this compound does not list this reaction.—Human trial
ZenagamtideNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—Human trial
PemvidutideNot listed in the source checkedThe label or study checked for this compound does not list this reaction.—Human trial

A blank result means the label or study checked here does not list the reaction. It does not prove the reaction cannot happen, and it does not replace the full prescribing information. A pharmacist or clinician can review the complete label alongside the rest of a person’s medicines.

What people reported to the FDA

The first table summarizes labels and published trials. This table shows reports filed with the FDA after the medicines went on sale. Each percentage is the share of reports for that product that mention this symptom—not the share of patients who experienced it.

Each GLP-1 brand in the FDA snapshot, and what share of its reports names this symptom.
ProductShare of its own reportsAll reports
Saxendaliraglutide4.3% of Saxenda reports10,040 reports
Wegovysemaglutide4.2% of Wegovy reports21,044 reports
Ozempicsemaglutide4.2% of Ozempic reports66,161 reports
Rybelsussemaglutide4.0% of Rybelsus reports7,379 reports
Zepboundtirzepatide3.5% of Zepbound reports70,141 reports
Victozaliraglutide3.2% of Victoza reports44,086 reports
Trulicitydulaglutide2.8% of Trulicity reports88,332 reports
Mounjarotirzepatide2.7% of Mounjaro reports93,975 reports

A row reading “below” is not a zero. The snapshot keeps each product’s 25 most-reported terms, so a term missing from that list was either never reported or reported and ranked 26th. All that can be proved is that it sits under the 25th. Read from FDA on 2026-08-17.

Reports are not rates and a report is not proof the drug did it. How to read this data, and the questions it answers on its own.

3Read deeperWhy it happens, when it appears, and what the page proves

Why tiredness is plausible on this class, and why plausible is not proven

Several routes to tiredness sit on these sources already, without needing a new mechanism. Energy intake falls, sometimes sharply — decreased appetite is a listed reaction. Stomach and gut reactions cost fluid. And for anyone taking one of these compounds alongside insulin or a sulfonylurea, low blood sugar is a labeled risk. It shows up as weakness, shakiness and trouble concentrating rather than announcing itself as a blood sugar problem.

None of that is an attribution. Someone starting one of these compounds is usually changing several things at once: what they eat, how much, when, and often how they sleep. A reaction table cannot separate the compound from everything else going on around it. What the labeled records establish is that fatigue was recorded and reported at the band the table prints. Everything past that is a clinical question about one person.

Fatigue is also the reaction most likely to have another explanation entirely, several of which are worth finding. That is the practical argument for raising it rather than absorbing it.

The labeled cause of weakness that is not fatigue

Hypoglycemia (with insulin or a sulfonylurea) is also listed for Tirzepatide (serious — monitor) and Semaglutide (serious — monitor). Each result links to its original source.

Low blood sugar matters on a fatigue page for three reasons. It gets mistaken for ordinary tiredness. It is a listed reaction rather than a guess. And the combination that produces it — one of these compounds alongside insulin or a sulfonylurea — is visible on a medicine list. That makes it the first thing a prescribing clinician can rule in or out.

What the split between labeled and investigational records tells you

A prescribing document is assembled from trials that recorded every event occurring to every participant, related or not, and reported them against a control group. That machinery is why a reaction as unspecific as fatigue reaches a label at all: it survives the comparison with placebo.

A phase 2 paper may only highlight the side effects that differed most between groups. For these drugs, that usually means stomach and gut problems. If fatigue is missing from an early trial report, that does not prove the drug causes less fatigue.

The practical consequence is narrow. Only the labeled rows in the table above support a comparison, and even they only support one between the two drugs that carry a band.

What the evidence shows—and what remains unknown

Fatigue is the reaction where the gap between what a table shows and what a reader wants from it is widest.

The claimWhat the evidence shows
Fatigue is a recognized reaction on these compounds.Supported for the two FDA-labeled records, at the band each label states. It is not supported as a class-wide statement, because the investigational records here do not carry it.
My tiredness is caused by the medicine.Not supported by any table. Pinning down a cause in one case is a clinical judgment. It weighs the medicine list, the timing, the diet and everything else that changed. A published frequency band sees none of that.
The investigational compounds are less tiring.Not supported. Their trial reports emphasize the reactions that separated the arms. Silence in a paper is not a measurement of absence, and treating it as one compares documents rather than compounds.
It wears off as the body adjusts.Not supported. Some sources say stomach and gut side effects ease while a dose is held, but they do not say the same about fatigue.
Feeling drained is just part of losing weight.Unestablished, and a costly assumption. Several listed causes of weakness on these same records can be found and named. One of them is tied to a specific medicine combination. That is exactly the sort of thing that gets missed when a symptom is filed under expected.

When tiredness is a reason to make contact

Fatigue on its own is rarely urgent. This section exists for a reason. Two of the serious reactions listed on these sources show up as weakness, dizziness or trouble concentrating, and nothing more specific. Both are worth catching early.

Acute kidney injury from dehydration

Prompt

Signs: Vomiting or diarrhea bad enough that you cannot keep fluids down, passing much less urine than usual, dizziness when you stand up, or unusual weakness.

The label links the risk to dehydration, so ongoing fluid loss is worth reporting early. A clinician can check kidney function.

Hypoglycemia when combined with insulin or a sulfonylurea

Prompt

Signs: Shakiness, sweating, confusion, sudden hunger, a racing heart, blurred vision or trouble concentrating — especially in someone also taking insulin or a sulfonylurea.

The source ties this risk to that combination specifically, which makes your full medicine list worth going through with whoever prescribes for you. Severe confusion, a seizure or passing out is an emergency call.

Recognition is the only job of this section. Assessment belongs to a clinician, who can weigh a symptom against the rest of the picture in a way no page can.

EmergencySome symptoms should not wait for an appointment. Call emergency services (911 in the US) if they are severe, getting worse fast, or involve trouble breathing, chest pain, fainting or confusion.

Common questions

Is fatigue listed on the Mounjaro label?

The tirzepatide label lists fatigue as a common side effect. The table above shows the reported frequency.

Mounjaro and Zepbound contain the same drug but have different approved uses and separate prescribing labels. Check the label for the specific product you use.

How long does Mounjaro fatigue last?

No label or trial reports a set duration for fatigue.

It is worth noticing what the sources do and do not commit to. They describe stomach and gut side effects as easing while a dose is held; they say nothing equivalent about fatigue. Pages that answer this with some number of weeks are extending a statement about one reaction onto another.

Does semaglutide cause fatigue as well?

Yes. The semaglutide and tirzepatide labels both list fatigue in the same frequency range.

The two labels agree, but they are not a head-to-head trial. Their frequency ranges cannot rank one drug as better than the other.

Is fatigue worse when the dose goes up?

The labeled records band this reaction without splitting it by dose, so they do not answer that question.

What the sources do describe is that reactions cluster around the start of treatment and around each increase. The approved schedules hold each step for a stated minimum before the next one is considered. That is a pattern, not a prediction, and pacing is a decision for the prescribing clinician.

Could the tiredness be low blood sugar rather than the compound?

It could. The pages here name the circumstance in which that is a labeled risk: taking one of these compounds alongside insulin or a sulfonylurea.

Low blood sugar presents as shakiness, sweating, sudden hunger, a racing heartbeat or difficulty concentrating, which overlaps almost entirely with what people describe as fatigue. The medicine list is what distinguishes them, and the prescriber holds it.

Should I stop taking it if I am exhausted?

Your prescribing clinician should decide whether to hold, change or stop a dose.

Bring specifics to that conversation: when it started relative to a dose change, what you are eating now, what else is on the medicine list, and whether anything else changed at the same time. A precise account is worth more at an appointment than a vague one. It is also the part only the person taking the compound can supply.

Is fatigue the same as the tiredness people report after eating less?

The studies do not separate those possible causes.

Energy intake falls on these compounds by design — decreased appetite is a listed reaction on several records here. Whether one person’s tiredness runs through that route, through the compound directly, or through something unrelated is a clinical question. The honest position is that a reaction table cannot settle it.

Want the full picture for one compound? Open its guide for uses, dosage information, side effects and serious warnings.

Tirzepatide reactions in full, including fatigue

Information from an approved label behind tirzepatide, apart from fatigue.

What else semaglutide lists besides fatigue

Including the semaglutide boxed warning, on the semaglutide page rather than on fatigue.

Constipation read the same way as fatigue

8 of 36 pages carry constipation, counted class-wide rather than within fatigue.

Nausea across every page, as with fatigue

Which sources name nausea, under what wording and at what frequency, beyond fatigue.

All source-checked pages, not only those listing fatigue

From label-backed entries to compounds with no established human dose, including Fatigue

Every AOD-9604 reaction, not only fatigue

4 common and 1 serious AOD-9604 reactions, in full past fatigue.

Every Melanotan II reaction, not only fatigue

3 common and 5 serious Melanotan II reactions, in full past fatigue.

Reading fatigue for a length nobody published

Three different questions hide inside this one, and each needs a different study, including fatigue

PT-141 reactions in full, including fatigue

Information from an approved label behind PT-141, apart from fatigue.

Every symptom in this section is listed on the symptom questions index.

Questions readers ask

How can I combat fatigue on Mounjaro?

No cited study tests a treatment for fatigue. The labels do identify other possible causes, including low blood sugar and dehydration, that a clinician can check.

Low blood sugar is a labeled risk when one of these compounds sits alongside insulin or a sulfonylurea. Dehydration bad enough to affect the kidneys is on the same records. A medicine list is what tells those apart, and the prescriber holds it.

What are four warning signs of fatigue?

The labels list fatigue as a side effect, but they do not give a four-sign checklist for it.

They do name what low blood sugar looks like: shakiness, sweating, sudden hunger, a racing heartbeat, trouble concentrating. That overlaps almost entirely with what people call tiredness, which is why a prescriber rules it in or out first.

How to get rid of fatigue on GLP-1?

None of the cited sources evaluates a treatment for tiredness, so no treatment is suggested. The useful finding is which labels list fatigue and which early trial reports do not.

Both labeled records list it. The investigational trial reports mostly do not, which says more about how each document was written than about the compounds. Bring specifics to an appointment: when it started against a dose change, and what else changed at the same time.

37primary sources, each with the day we read it — open the documents used on this page