Quick answer: the most common GLP-1 side effects are nausea, diarrhea, vomiting, constipation, indigestion, burping and stomach pain. They usually show up after the first dose or a dose increase and ease over days to a few weeks as your body adjusts. Call your doctor for vomiting or diarrhea that stops you keeping fluids down, severe stomach pain that may spread to your back, signs of dehydration, or yellowing skin or eyes. Get emergency care for trouble breathing or swelling of the face or throat.
Educational only, not medical advice. This article explains general information and quotes official labels where noted. It doesn't recommend any dose or change to your treatment. Follow your prescriber's instructions and the product label.
Which side effects are most common?
The labels for Zepbound, Mounjaro, Wegovy and Ozempic list digestive effects as the most frequent in trials: nausea, diarrhea, vomiting, constipation, abdominal pain, dyspepsia (indigestion), burping and bloating. Most were mild to moderate and happened most often while the dose was being increased.
How long do GLP-1 side effects last?
For most people, digestive effects are worst in the first 1 to 3 days after a shot, especially in the first weeks and after each dose step, then settle. In trials they became less frequent over time on a stable dose. If a side effect isn't easing after a few weeks, or gets worse, talk to your prescriber. Slowing the pace of dose increases is their call.
What about vomiting in the first week?
Some nausea and the occasional vomit after the first dose is common. What matters is whether you can keep fluids down. Small sips, bland food, smaller meals and stopping eating when full help many people. Call your doctor if you can't keep fluids down for a day, you see blood, or you feel dizzy, very thirsty or are peeing much less. The labels warn that dehydration from vomiting and diarrhea can harm the kidneys.
Diarrhea or constipation?
Both are common, and some people swing between them. For diarrhea: fluids with electrolytes, and fewer greasy foods. For constipation: fluids, fiber, movement, and ask a pharmacist about over-the-counter options. Call your doctor if either lasts more than a few days, comes with severe pain, or you can't pass gas.
Gas, bloating, burping and heartburn
GLP-1s slow how fast your stomach empties, so food sits longer. That can cause bloating, gas, reflux and sulfur burps. Smaller meals, eating slowly, less fat and fizzy drinks, and not lying down soon after eating are common tips.
Headaches
Headache appears on the Wegovy label and is reported with other GLP-1s. Common triggers are dehydration and eating much less than usual. Persistent or severe headaches are worth a call.
Feeling cold
Many people report feeling colder on GLP-1s. It isn't a headline label side effect, and the reason isn't well studied. Eating less and losing body weight are plausible factors. If it comes with tiredness, hair changes or weight gain, ask your doctor to check thyroid levels.
Joint or muscle aches
Some people report aches. They aren't among the most common label reactions. Possible factors include dehydration, changes in activity and less protein. Joint pain with swelling, redness or fever needs a doctor.
Hair shedding
Hair loss was reported more often than with placebo on the Zepbound and Wegovy labels and is usually linked to rapid weight loss. See hair loss on Wegovy or Zepbound.
When should you call your doctor right away?
The labels list these warnings. Contact your provider promptly, or get emergency care if severe:
- Severe stomach pain that won't go away, with or without vomiting, possibly spreading to your back (possible pancreatitis).
- Pain in the upper right belly, fever, yellow skin or eyes, or clay-colored stools (possible gallbladder problems).
- Signs of dehydration or much less urine.
- A lump or swelling in the neck, trouble swallowing or hoarseness.
- Signs of a serious allergic reaction: swelling of the face, lips, tongue or throat, trouble breathing, severe rash.
- Low blood sugar symptoms if you also take insulin or a sulfonylurea.
- Changes in vision if you have diabetes, and mood changes or thoughts of self-harm.
Tracking it in Caliper
Caliper's check-ins let you rate side effects by severity, and the side effects vs dose chart lines those ratings up against your dose steps. You can see whether nausea peaks on day 2 after a shot, or eased after a few weeks on a dose. A PDF report brings that history to your provider. Caliper doesn't judge whether a symptom is normal. Your provider does.
FAQ
What are the most common GLP-1 side effects?
Nausea, diarrhea, vomiting, constipation, indigestion, burping and stomach pain, mostly mild to moderate and most frequent while the dose is being increased.
How long do GLP-1 side effects last?
They are usually worst in the first days after a shot and after each dose increase, and ease over days to a few weeks on a stable dose. Talk to your prescriber if they don't ease.
Is vomiting normal in the first week on Zepbound or Wegovy?
Occasional nausea or vomiting is common early on. Call your doctor if you can't keep fluids down, see blood, or have signs of dehydration.
Why do I feel cold on a GLP-1?
Many people report it, but it isn't a headline label side effect and isn't well studied. Eating less and losing weight may play a part. Ask your doctor if it persists.
When is a GLP-1 side effect an emergency?
Severe stomach pain that won't go away, signs of a serious allergic reaction, or trouble breathing need urgent care.
Sources
- Eli Lilly, Zepbound prescribing information
- Eli Lilly, Mounjaro prescribing information
- Novo Nordisk, Wegovy prescribing information
- Novo Nordisk, Ozempic prescribing information
Keep the whole picture in one place
Caliper is a GLP-1 and peptide tracker. It logs each dose, rates side effects in check-ins and charts them against your dose steps, with reminders and a PDF report for your provider. It never recommends or calculates a dose.
Track side effects with Caliper →
For adults 18+.
Medical disclaimer: This article is for general educational purposes only and is not medical advice. It does not recommend any dose, compound, product, supplier or protocol. Always follow your prescriber's instructions and the product label, and talk to a pharmacist or healthcare provider about any question regarding your medication.