GLP-1 Side Effects: What's Common, What's Serious, and How to Manage Them

Key takeaways

• Most side effects of GLP-1 medications involve the digestive system: nausea, diarrhea, constipation, vomiting, indigestion, and reduced appetite.
• These effects are usually mild to moderate and tend to show up when treatment starts or the dose goes up. For many people they ease with time.
• Eating smaller meals, stopping when you feel full, limiting greasy foods, staying hydrated, and increasing the dose slowly can all help.
• Less common but serious risks include pancreatitis, gallbladder problems, dehydration-related kidney injury, and severe stomach or bowel problems. Know the warning signs.
• In January 2026, FDA asked manufacturers to remove suicidal-thoughts warnings from the labels of GLP-1 weight-loss drugs after its review found no increased risk.
• Compounded GLP-1s are not FDA-approved, and the side-effect data below come from studies of FDA-approved, brand-name products.

About the research in this article

About the research: The side-effect rates in this article come from the FDA prescribing information for Wegovy (semaglutide) and Zepbound (tirzepatide). Both are FDA-approved, brand-name products, and their labels summarize the clinical trials that tested them. Compounded semaglutide and tirzepatide are not FDA-approved. FDA does not review compounded drugs for safety, effectiveness, or quality before they are marketed, so these results cannot be assumed to apply to compounded versions. Sources: FDA, FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss; FDA, FDA to Telehealth Companies: What to Know When Promoting Compounded Drugs.

Why GLP-1 medications cause side effects

GLP-1 medications such as semaglutide and tirzepatide mimic gut hormones that help regulate appetite and blood sugar. Tirzepatide also acts on a second hormone receptor, called GIP. One of the ways these medications reduce appetite is by slowing how quickly the stomach empties, which helps you feel full sooner and for longer.

That same effect explains most of the common side effects. When food stays in the stomach longer, large or rich meals are more likely to cause nausea, fullness, burping, or reflux. Changes in how the gut moves can also cause diarrhea or constipation. This is why digestive side effects tend to be most noticeable when treatment starts or the dose increases, and why how you eat can make a real difference.

The most common GLP-1 side effects

The FDA labels for Wegovy and Zepbound list digestive symptoms as the most common side effects. The table below shows how often selected side effects were reported in the brand-name trials compared with placebo (an inactive treatment).

Side effect	Wegovy 2.4 mg (semaglutide)	Zepbound 5–15 mg (tirzepatide)	Placebo (Wegovy / Zepbound trials)
Nausea	44%	25–29%	16% / 8%
Diarrhea	30%	19–23%	16% / 8%
Vomiting	24%	8–13%	6% / 2%
Constipation	24%	11–17%	11% / 5%
Abdominal pain	20%	9–10%	10% / 5%
Fatigue	11%	5–7%	5% / 3%
Hair loss	3.3%	4–5%	1% / 1%

Source: FDA prescribing information for Wegovy (revised 03/2026) and Zepbound (revised 04/2026). These figures come from separate trials with different designs and populations, so they should not be used to compare the two medications directly.

Nausea and vomiting

Nausea is the most commonly reported side effect. According to the Wegovy label, digestive side effects were reported most often during dose escalation. An expert consensus on managing these effects found that nausea tends to be most frequent in the first four to five weeks, and that episodes of vomiting usually resolve within days.

Diarrhea and constipation

Diarrhea usually appears early and is often short-lived. Constipation can start later and last longer. People sometimes drink less water because they feel full, which can make constipation worse.

Indigestion, reflux, and burping

Slower stomach emptying can lead to heartburn, a sour taste, burping, or bloating, especially after large or high-fat meals. The Zepbound label lists dyspepsia (indigestion) among its common side effects.

Fatigue, headache, and hair loss

Some people feel tired or get headaches, particularly early on, when they are eating much less. Hair loss was reported more often with the brand-name medications than with placebo. Hair shedding can also follow rapid weight loss in general, so it is worth discussing with a clinician if you notice it.

Injection site reactions

Redness, itching, or mild swelling where the medication is injected can occur. Rotating injection sites may help.

How long do GLP-1 side effects last?

For most people, digestive side effects are temporary. A multidisciplinary expert consensus published in the Journal of Clinical Medicine found that most digestive effects are mild to moderate, start during dose escalation, and often settle once a stable maintenance dose is reached. Constipation was the exception: it tended to last longer than other digestive effects.

Side effects can return briefly after each dose increase. If they don't improve, a clinician may suggest staying on the current dose longer, stepping back to a lower dose, or adjusting the treatment plan. Don't change your dose on your own.

How to manage common side effects

These strategies are drawn from expert consensus recommendations and nutrition guidance for people taking GLP-1 medications. They may help, but they are not a substitute for advice from your own clinician.

• Eat smaller meals, more slowly. Stop when you feel comfortably full rather than finishing the plate.
• Go easy on greasy, fried, and very rich foods. These are more likely to cause nausea and reflux when stomach emptying is slower.
• Stay hydrated. Sip fluids through the day, especially if you have vomiting or diarrhea. Dehydration can strain the kidneys.
• Build in fiber and movement for constipation. Fiber, water, and regular physical activity can help. Ask a clinician or pharmacist before starting a stool softener or laxative.
• Avoid lying down right after eating if you notice reflux or heartburn.
• Prioritize protein. Even when your appetite is low, protein at each meal and regular strength training help protect muscle, according to a 2025 joint advisory from four obesity and nutrition societies.
• Increase the dose gradually. Slower titration is one of the main tools clinicians use to improve tolerability.

Less common but serious risks

The FDA labels for Wegovy and Zepbound include warnings about several less common but serious risks. Knowing the warning signs helps you act early.

• Pancreatitis. Severe, persistent stomach pain, sometimes spreading to the back, with or without vomiting, needs prompt medical attention.
• Gallbladder problems. Gallstones and gallbladder inflammation occurred more often with the brand-name medications than placebo. The Wegovy label notes that substantial or rapid weight loss can raise gallstone risk. A 2022 meta-analysis of randomized trials found higher risk with higher doses, longer use, and use for weight loss. Watch for pain in the upper right abdomen, fever, yellowing of the skin or eyes, or clay-colored stools.
• Dehydration and kidney injury. Ongoing vomiting or diarrhea can lead to dehydration, which can affect kidney function.
• Severe stomach or bowel problems. The labels warn about severe digestive reactions. Postmarketing reports for Wegovy include bowel blockage (ileus) and severe constipation.
• Low blood sugar. The risk is higher in people who also take insulin or a sulfonylurea for diabetes, which may need dose adjustments.
• Thyroid C-cell tumors. Both labels carry a boxed warning because these drugs caused thyroid C-cell tumors in rodents. It is unknown whether this happens in humans. People with a personal or family history of medullary thyroid carcinoma or MEN 2 should not use them.
• Anesthesia and procedures. Because the stomach may still contain food despite fasting, the labels advise telling your care team before any surgery or procedure that involves anesthesia or deep sedation.
• Vision changes. In 2025, the European Medicines Agency concluded that NAION, an eye condition that can cause sudden vision loss, is a very rare side effect of semaglutide. Seek care promptly for any sudden change in vision.
• Allergic reactions. Swelling of the face, lips, or throat, trouble breathing, or a severe rash require emergency care.

What about mood and suicidal thoughts?

In January 2026, FDA asked manufacturers to remove warnings about suicidal behavior and ideation from the labels of Wegovy, Zepbound, and Saxenda. FDA's review of 91 placebo-controlled trials found that people taking GLP-1 medications did not have a higher risk of suicidal thoughts or behavior than those taking placebo. A large FDA Sentinel analysis of real-world data also found no increased risk of intentional self-harm.

That said, any new or worsening depression, anxiety, or thoughts of self-harm deserve attention. Talk to your clinician, and if you are in crisis, call or text 988 in the U.S.

Contraception and other medications

GLP-1 medications slow stomach emptying, which can affect how some oral medications are absorbed. The Zepbound label advises people who use oral hormonal birth control to switch to a non-oral method, or add a barrier method, for four weeks after starting and for four weeks after each dose increase. Give your clinician a full list of your medications and supplements before you start.

Extra considerations with compounded GLP-1s

FDA has received reports of adverse events, some requiring hospitalization, that may be linked to dosing errors with compounded injectable semaglutide. Some errors happened when patients measured doses themselves, and some when doses were miscalculated. FDA has also received reports of adverse events in people prescribed compounded semaglutide or tirzepatide at doses or schedules beyond the FDA-approved labels.

If you use a compounded GLP-1, confirm the concentration and dose in units and milliliters with your prescriber or pharmacist, use the syringes provided, and ask questions whenever a dose or vial changes.

When to contact a clinician

Contact your clinician if side effects interfere with eating or drinking, last more than a few days, or keep getting worse. Seek urgent care for:

• Severe or persistent abdominal pain
• Vomiting that keeps you from holding down fluids, or signs of dehydration such as dizziness or very little urine
• Yellowing of the skin or eyes, or fever with upper abdominal pain
• Sudden vision changes
• Signs of a severe allergic reaction

The bottom line

Side effects are common with GLP-1 medications, but most are digestive, mild to moderate, and temporary. They are often manageable with slower dose increases and changes to how you eat. Serious complications are less common, and knowing the warning signs matters. Your history, other medications, and goals all shape whether a GLP-1 is a good fit and how to start it safely.

If you are considering a GLP-1 medication or have questions about side effects, you can browse common questions or learn about Stone Health's clinician-guided approach to weight care. A licensed clinician can help you decide whether treatment may be appropriate for you. For more on midlife changes, see our guide to menopause weight gain.