GLP-1 Side Effects: What Is Normal, What Helps, and When to Call Us

Nearly everyone who starts semaglutide (Wegovy, Ozempic) or tirzepatide (Zepbound, Mounjaro) asks the same two questions: is this normal, and what do I do about it? Most side effects are predictable and manageable; a few need a same-day call.

Why these medications cause side effects

Both medications mimic gut hormones. They slow stomach emptying, quiet appetite, and make a modest meal feel large. Food sits longer, so a normal plate can bring nausea, bloating, belching, or reflux. Eating and drinking less can bring constipation, fatigue, and lightheadedness. Neither medication is recommended for people with severe gastroparesis.

The prescribing information shows how common this is. Among adults taking Wegovy 2.4 mg, nausea affected 44% (versus 16% on placebo), diarrhea 30% (16%), vomiting 24% (6%), and constipation 24% (11%). With Zepbound, nausea affected 25% to 29% (8% on placebo) and constipation 11% to 17% (5%).

Two details matter more. Both labels note that these reactions were reported most often during dose escalation, and Zepbound's adds that they decreased over time. And few people had to stop: 4.3% of Wegovy patients and 1.9% to 4.3% of Zepbound patients discontinued for digestive reasons, versus under 1% on placebo.

Nausea, vomiting, and reflux: what helps

A 2023 multidisciplinary consensus reports that nausea peaks in the first four to five weeks and that episodes usually resolve within about eight days. It recommends small, frequent meals, hydration, and slow dose increases. Our advice builds on that:

• Eat smaller meals, more often, and slowly. Stop at the first sign of fullness.
• Go easy on fatty, fried, and very sweet foods, which sit longest in a slowed stomach.
• Stay upright for an hour or two after eating, and keep dinner light if reflux bothers you at night.
• Sip fluids through the day. Dehydration is the usual way these medications strain the kidneys.

If nausea persists despite these steps, the consensus supports adding an anti-nausea or prokinetic medication, and lowering the dose if that medication is still needed after a month at the maintenance dose.

Dose pacing: the tool patients forget they have

Both labels build in flexibility. Wegovy's allows a four-week pause before the next step if a dose is not tolerated, and a maintenance dose of 1.7 mg or 2.4 mg depending on response and tolerability. Zepbound's requires at least four weeks on each dose before increasing, and allows a lower maintenance dose if the higher one is not tolerated. The goal is the dose you can live with, not the top of the ladder.

Missed doses have rules too (see the questions below). If you are unsure what to do before your next dose, call us first, and never double up.

Constipation and diarrhea

Constipation is the side effect that lingers. In trial data summarized by the consensus, diarrhea episodes lasted about three days, while constipation lasted a median of 47 days. The fix is unglamorous: more fluids, more fiber from vegetables, fruit, beans, and whole grains, and daily movement, with a fiber supplement or stool softener if needed. If you need a laxative for more than a few days, tell us.

For diarrhea that persists, the consensus suggests an antidiarrheal such as loperamide and a review of other medications, such as metformin, that can contribute.

Fatigue, hair shedding, and the "Ozempic face"

Fatigue was reported by 11% of Wegovy patients (5% on placebo) and 5% to 7% of Zepbound patients (3%). In our experience the usual contributors are too few calories, too little protein, too little fluid, or poor sleep. If it persists after those are fixed, we check labs.

Hair shedding appears in both labels: 3% on Wegovy versus 1% on placebo, and 4% to 5% on Zepbound versus 1%, far more often in women. Both labels say it was associated with the weight reduction. Dermatologists call this telogen effluvium: a shock to the body, including losing 20 pounds or more, pushes many hairs into the resting phase at once. The American Academy of Dermatology notes that shedding usually appears a few months after the trigger and that fullness tends to return within six to nine months, though it can continue while the stressor persists and a direct drug effect has not been ruled out. A dermatologist quoted by the Academy advises people prone to hair loss to lose weight slowly and to take a standard daily multivitamin.

The "Ozempic face" is mostly a weight-loss effect. Lose a meaningful amount of fat and the face loses fat too, which can read as hollowing, sagging, or new lines. Dermatologists quoted by the Academy say rapid weight loss is partly responsible and that the drugs may also affect collagen and muscle. In our practice we prefer to wait until weight has been stable for several months before discussing fillers, collagen stimulators, or microneedling, because the face keeps changing until then.

When to call us the same day

Most of the above can wait for your next check-in. These cannot. Call us, or seek emergency care if symptoms are severe:

• Severe or persistent abdominal pain, with or without nausea or vomiting, sometimes spreading to the back. This can signal pancreatitis; the medication is stopped until it is evaluated.
• Upper abdominal pain with fever, yellowing of the skin or eyes, or clay-colored stools, which can mean a gallbladder problem.
• Vomiting or diarrhea that will not stop, inability to keep fluids down, dark or scant urine, or dizziness on standing. Dehydration is the usual way these medications injure kidneys.
• Swelling of the face, lips, tongue, or throat, trouble breathing or swallowing, or a severe rash.
• A lump or swelling in the neck, hoarseness, trouble swallowing, or shortness of breath. Both medications carry a boxed warning about thyroid C-cell tumors seen in rodents; neither is prescribed to anyone with a personal or family history of medullary thyroid carcinoma, or who has MEN 2.
• Shakiness, sweating, confusion, or a fast heartbeat if you also take insulin or a sulfonylurea, which raise the risk of low blood sugar.
• A heart that races or pounds for several minutes, or any vision change if you have type 2 diabetes.
• New or worsening low mood or thoughts of self-harm. In January 2026 the FDA concluded, from 91 trials and a database study of more than two million people, that the evidence does not support a causal relationship, and asked for that warning to be removed. We still want to hear about any mood change; in a crisis, call or text 988.

Two situations need a conversation in advance. First, surgery, endoscopy, or any procedure with sedation. Both labels now warn about rare reports of stomach contents entering the lungs under anesthesia. A 2024 multi-society guidance says patients without risk factors for a slowed stomach may continue the medication, but the risk factors include the escalation phase, higher doses, active digestive symptoms, and weekly dosing, so expect the question. You may be asked to follow a liquid diet for at least 24 hours or to skip the dose the week before. Tell every clinician involved.

Second, pregnancy. Both should be stopped if a pregnancy is recognized, and Wegovy's label also says to stop at least two months before a planned pregnancy because semaglutide stays in the body a long time. Zepbound can weaken birth control pills for four weeks after starting and after each dose increase, so its label advises a non-pill or added barrier method during those windows.

One last note. Compounded semaglutide and tirzepatide are not FDA-approved products, and by May 2026 the FDA had received more than 1,700 adverse event reports involving them, some linked to measuring errors or doses beyond the approved schedule. If you use any product drawn from a vial, confirm the exact volume with us or your pharmacist rather than estimating.

The bottom line

Digestive side effects are the price of admission for many people in the first months, and they usually ease with food choices, fluids, and patient dosing. Hair shedding and facial changes come mostly with the weight loss and generally settle. If you are struggling on one of these medications, or weighing whether to start, book a complimentary consultation. We will review your dose and your plan.

Website content is for general education and does not replace individualized medical advice, diagnosis, or treatment. Individual results vary. This article is general education from a Florida physician and does not create a doctor–patient relationship; talk with your own clinician about your situation.