Fatigue on GLP-1s and peptides: what to track, when it tends to show up, and how to log it
Fatigue is listed on the weight-management GLP-1 labels: Wegovy 11% versus 5% on placebo, Saxenda 7.5% versus 4.6%, Zepbound 5–7% versus 3%. It is not among the tabulated reactions for Ozempic or Mounjaro. Many people report it in the first days after a shot and during escalation. Log fatigue 1–5 with energy and sleep scores, and compare against shot days and how much you ate.
GLP-1 fatigue: what it is and who reports it
GLP-1 fatigue is the flat, heavy-limbed tiredness that many people notice in the first weeks on semaglutide or tirzepatide, and often again in the day or two after each weekly shot. It is one of the few non-gut side effects with a label figure, but only on the weight-management labels.
| Label | Fatigue (drug) | Fatigue (placebo) |
|---|---|---|
| Wegovy 2.4 mg | 11% | 5% |
| Saxenda | 7.5% | 4.6% |
| Zepbound 5 / 10 / 15 mg | 5% / 6% / 7% | 3% |
| Ozempic, Mounjaro | not among the tabulated reactions | |
Ozempic's and Mounjaro's tables only list reactions at or above 5%, and fatigue does not make that cut in the diabetes trials. That does not mean nobody on Ozempic gets tired; it means the label cannot give you a number. Compounded Compounded Semaglutide and Compounded Tirzepatide have no label at all.
Peppy also flags fatigue as common for injectables in general, including research compounds like BPC-157 and CJC-1295 / Ipamorelin. There is no prescribing information for those, so there are no figures, only what people report.
When it tends to show up
The labels do not discuss fatigue timing. Their general statement, that reactions cluster in dose-escalation weeks and ease over time, is about the gut, and it may or may not carry over.
People's reports fall into three rough groups. The first is shot-day fatigue: a heavy day or two after each weekly dose, often alongside nausea. Zepbound's label puts median peak concentration at 24 hours (range 8 to 72), which is at least consistent. The second is escalation fatigue: a tired week or two after each step-up, then a return to normal. Wegovy steps every four weeks; Zepbound at least four weeks apart. The third is under-eating fatigue: a slow slide that tracks with how little you have been eating and drinking, and that has less to do with the shot than with the appetite effect.
The three look identical on a single day. They look completely different across a month of logs, which is the whole point of logging.
What is worth logging
- Fatigue, 1–5, daily. Score the day overall, not the worst hour.
- Energy and sleep as feelings, 1–5. These are separate scales in Peppy and both are on by default. Fatigue with good sleep and fatigue with bad sleep are different findings. See insomnia.
- How much you ate and drank, in the note. "Two small meals", "forgot to drink", "normal day". Peppy does not log food or calories, and a note is enough.
- Days since the shot, and the dose you were on. Log the shot in the same app so the offset and dose come for free.
- Dizziness alongside. Tired plus light-headed is a different signal from tired alone. Peppy tracks dizziness separately.
- Weight. A fast drop in a tired week is worth seeing on the same timeline. The Apple Health weight guide covers the setup.
When to contact your prescriber
Fatigue is not a red-flag reaction on any GLP-1 label. Some of the things that cause it are.
- Low blood sugar. Wegovy's label says it "lowers blood glucose and can cause hypoglycemia" and tells prescribers to educate patients on the signs. The labels list hypoglycemia in patients with type 2 diabetes at 6% (Wegovy) and 12.6% (Saxenda). Shaky, sweaty, confused tiredness is a same-day call, especially if you also take insulin or a sulfonylurea.
- Dehydration. The labels link nausea, vomiting or diarrhea leading to dehydration to acute kidney injury. Fatigue with dizziness in a diarrhea week is that pattern.
- Fatigue that is getting worse over weeks, not better. That does not match the label's "decreases over time" description and deserves a conversation, with the log.
How to do this in Peppy
- Turn fatigue on. It is not a GLP-1 default, so open Settings ▸ Tracking and toggle Fatigue. Energy and Sleep are already on in the feelings list below it.
- Score all three in the daily check-in. Tap the check-in row on the Today tab. Fatigue 1–5 under side effects, energy and sleep 1–5 under feelings, then the food-and-drink note and your weight.
- Log each shot with the body map. Tap the dose on the Today tab, pick the site, save. If you run a titration ladder (Pro), the dose you were on is recorded and becomes a step-up marker.
- Read the Progress tab (Pro). The fatigue row on the weekly heat-map sits above the feelings charts for energy and sleep, all on one axis with step-ups marked. Fatigue rising while sleep falls points one way; fatigue rising while the weight trend drops fast points another. Free users see the charts blurred.
- Use the Calendar for shot-day fatigue. Flip the week strip and compare check-ins on days one and two after the shot with days five and six. If the tired days are always the same two, you have a shot-day pattern.
- Set a check-in reminder (Pro) in Settings ▸ Reminders. Fatigue is the side effect most likely to make you skip the log.
Related: the side-effects tracking guide, low blood sugar, and the Saxenda tracker.
Track it in Peppy
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Free · iPhone · no accountFrequently asked
Does Wegovy make you tired?
Wegovy's label lists fatigue in 11% of participants versus 5% on placebo. It sits below nausea, diarrhea, vomiting, constipation, abdominal pain and headache in the label's table. Saxenda's label lists 7.5% versus 4.6%; Zepbound's lists 5%, 6% and 7% at 5, 10 and 15 mg versus 3%.
Why do GLP-1s cause fatigue?
The labels list fatigue without a mechanism. Many people report it alongside eating much less, poor sleep from nausea, or dehydration from diarrhea, which is why logging energy, sleep and food intake next to the fatigue score is more useful than the score alone.
How long does GLP-1 fatigue last?
The labels do not give a duration. Their general statement is that adverse reactions cluster during dose escalation and decrease over time. Many people report fatigue for a day or two after each weekly shot and for a week or two after each step-up, but that is anecdote. Your log will show your own pattern within a month.
Is fatigue a side effect of peptides like BPC-157 or CJC-1295?
No prescribing information exists for research compounds, so there are no incidence figures. Fatigue is commonly reported by people using injectable peptides, which is why Peppy flags it as common for injectables, but treat that as anecdote.
Should I tell my doctor about fatigue on a GLP-1?
Yes if it is persistent, getting worse, or comes with dizziness, very low food or fluid intake, or signs of low blood sugar. Wegovy's label says it lowers blood glucose and can cause hypoglycemia, and the labels link dehydration from GI reactions to acute kidney injury. Bring the log.
Sources
Not medical advice. Peppy is a tracking tool, not medical advice. Dose calculations are mathematical conversions only. Always follow your prescriber's instructions and verify every draw-up yourself.