"Does GLP-1 make you tired?" has an answer printed on most of the labels: yes, for a minority, and more often at higher doses. What the labels do not allow is a ranking. Each company builds its fatigue row from a different list of terms, so the number in the "fatigue" cell of one label is not the same measurement as the number in the next.
This page reads the current US prescribing information for seven GLP-1 products, retrieved from FDA's label service and DailyMed on 25 September 2026, and reports what each counts. It is one symptom across the class. Each drug's full record is on its own page — Wegovy, Zepbound, Mounjaro, Ozempic — and the class picture is on the GLP-1 side effects hub.
The rates, label by label
"Excess per 100" is our arithmetic: the drug rate minus the placebo rate in the same table. It is the number of extra people per 100 who reported tiredness, and it is the fairest way to read a single label.
| Label (trials) | Placebo | Drug, by dose | Excess per 100 at the top dose |
|---|---|---|---|
| Wegovy 2.4 mg, three weight trials (2,116 on drug) | 5% | 11% | 6 |
| Wegovy 2.4 vs 7.2 mg, two 72-week trials | 5% | 9% · 11% | 6 |
| Zepbound, weight Studies 1 and 2 | 3% | 5% · 6% · 7% (5, 10, 15 mg) | 4 |
| Foundayo, Trials 1 and 2 (about 3,150 on drug) | 4% | 6% · 7% · 9% (5.5, 9, 17.2 mg) | 5 |
| Saxenda, weight trials (3,384 on drug) | 4.6% | 7.5% | 2.9 |
| Trulicity, diabetes placebo pool | 2.6% | 4.2% · 5.6% (0.75, 1.5 mg) | 3.0 |
| Mounjaro, diabetes placebo pool | — | no fatigue row (below the table's 5% threshold) | — |
Two patterns hold across every label that prints doses. The rate climbs with the dose, one or two points per step. And the weight-management labels print higher rates than the diabetes labels — though the trials differ in population, length and dose, and the labels themselves say rates from different programmes "cannot be directly compared".
The row that is not the same row
The finding worth carrying away is in the footnotes. Each label defines its fatigue row differently:
| Label | What its "fatigue" row includes |
|---|---|
| Saxenda | fatigue only — asthenia (weakness) has its own row, 2.1% against 0.8% |
| Wegovy | fatigue and asthenia |
| Trulicity | fatigue, asthenia and malaise |
| Zepbound | asthenia, fatigue, lethargy and malaise |
| Foundayo | fatigue and "other related terms", unnamed |
A four-term bucket will generally catch more reports than a one-term bucket of the same underlying experience. So Zepbound's 7% and Saxenda's 7.5% are not a like-for-like pair: Saxenda's figure could be higher if its separate weakness row were folded in the way Zepbound's is. Any ranking of GLP-1 drugs by "fatigue rate" taken from the labels compares buckets of different sizes.
The two labels with no fatigue number
Mounjaro. Its placebo-controlled table lists reactions reported by at least 5% of patients, and fatigue is not on it — so among the 718 patients with type 2 diabetes who took Mounjaro in that pool, fatigue stayed below 5%. The label does add one line from SURPASS-CVOT, its heart trial: fatigue in 10% of patients on Mounjaro. That trial compared Mounjaro with dulaglutide (Trulicity), not placebo, and the sentence gives no comparator rate, so the 10% cannot be turned into an excess.
Ozempic. The injection label names fatigue, with taste change and dizziness, among "other adverse reactions with a frequency of >0.4%". There is no rate. The current label for the Ozempic and Rybelsus tablets does not mention fatigue at all.
What the labels say about why
Nothing directly. None of the seven labels gives a mechanism for fatigue. They do list, as separate warnings, three things that can leave a person weak or tired:
- Eating much less. Decreased appetite is itself a counted reaction — 11% on Mounjaro 15 mg against 1% on placebo. How protein intake fits into this is on our protein and GLP-1 page.
- Dehydration. Every label warns of kidney injury from fluid loss after vomiting or diarrhoea.
- Low blood sugar, when a GLP-1 is combined with insulin or a sulfonylurea. On Mounjaro added to basal insulin, blood glucose below 54 mg/dL occurred in 14% to 19% of patients against 13% on placebo.
Which, if any, applies to one person is for their clinician to work out. How side effects in general scale with dose is on our dose and side effects page.
What this page cannot tell you
- How long it lasts. None of the labels reports the duration of fatigue.
- Whether it is the drug. A trial rate says fatigue was reported more often, not that each report was caused by the drug.
- What anyone should do about it. Persistent tiredness, dizziness or weakness is something to raise with the prescriber, who can check for dehydration, low blood sugar or another cause.
Sources
- WEGOVY (semaglutide) prescribing information, Novo Nordisk, SPL effective 2026-06-18 — DailyMed, section 6.1 tables and footnotes.
- ZEPBOUND (tirzepatide) prescribing information, Eli Lilly, effective 2026-08-28 — DailyMed, Table 1 and footnote e.
- MOUNJARO (tirzepatide) prescribing information, Eli Lilly, effective 2026-08-27 — DailyMed, section 6.1 and Table 2.
- FOUNDAYO (orforglipron) prescribing information, Eli Lilly, effective 2026-07-29 — DailyMed, Table 1.
- SAXENDA (liraglutide) prescribing information, Novo Nordisk, effective 2026-02-25 — DailyMed, section 6.1.
- TRULICITY (dulaglutide) prescribing information, Eli Lilly, effective 2026-06-16 — DailyMed, Table 1 and footnote d.
- OZEMPIC (semaglutide) injection prescribing information, Novo Nordisk, SPL effective 2026-06-01 — DailyMed; OZEMPIC and RYBELSUS tablets, effective 2026-01-30 — DailyMed.