GLP-1 Side Effects in the First Week

What the label lists as the most common side effects

The Wegovy patient information lists these as the most common side effects in adults and children 12 and older:

• nausea, vomiting and diarrhea
• constipation
• stomach (abdomen) pain, upset stomach and feeling bloated
• belching, gas and heartburn
• headache, dizziness and tiredness (fatigue)
• changes in skin sensations
• stomach flu
• low blood sugar in people with type 2 diabetes
• hair loss

MedlinePlus, the National Library of Medicine's drug guide, gives a similar list for semaglutide injection. It adds runny nose or sore throat. It says to tell your doctor if any of these are severe or don't go away.

Most of this list involves your gut. That's because GLP-1 medicines slow how fast your stomach empties. Food stays with you longer, so you feel full sooner, and eating too much or too fast can backfire.

Is there a day-by-day timeline?

Not an official one. Neither label gives a day-by-day schedule for week one, and how you feel can vary a lot from person to person. What the Ozempic prescribing information does say is that the majority of reports of nausea, vomiting and diarrhea occurred during dose escalation, the period when the dose is stepped up.

In practice, that means:

• The first few doses are low on purpose. The label's step-up schedule is designed to reduce stomach side effects.
• Stomach effects tend to cluster around dose changes. You may notice them again when your dose goes up.
• If you can't tolerate a step-up, tell your prescriber. The Wegovy label says a prescriber may consider delaying the next increase.

Don't change your dose or schedule on your own. Keep a short daily note of what you ate and how you felt, so you have real details to share at your next check-in.

Nausea: the most common first-week complaint

For many people, nausea is the main thing they notice early on. Some habits that help:

• Eat small amounts. Your stomach empties more slowly, so a normal portion can feel like too much.
• Stop at the first sign of fullness. Don't wait until you feel stuffed.
• Go easy on greasy and fried food. The Academy of Nutrition and Dietetics says high-fat foods may be harder to digest on these medicines, especially on injection day.
• Sip clear liquids often. MedlinePlus suggests drinking small amounts of clear liquids often when you're nauseated.

For a full list of foods that tend to sit well, see our guide on what to eat when a GLP-1 makes you nauseous.

The first week is easier when you can see patterns, like which meals sat well and which didn't. Olive is a health companion that checks in with you every day, looks at what you eat, and helps you build small habits that actually hold. It doesn't diagnose or treat anything, so side-effect questions stay with your prescriber.

Diarrhea, constipation, burps and heartburn

Diarrhea. Loose stools can show up early. Fluids matter most here, because diarrhea drains them quickly. Our guide to what to eat with GLP-1 diarrhea covers gentle foods.

Constipation. Slower digestion can also go the other way. Fluids, fiber from food and regular movement are the usual first steps. Ask your prescriber before using a laxative.

Burps and heartburn. Belching and heartburn both appear on the Wegovy list. If your burps smell like eggs, see our page on Ozempic sulfur burps. For reflux, especially at night, see heartburn and reflux on a GLP-1.

Why fluids matter so much in week one

The Wegovy patient information warns about dehydration leading to kidney problems. It explains that diarrhea, nausea and vomiting may cause a loss of fluids, which may cause kidney problems. It says it's important to drink fluids to help reduce your chance of dehydration.

MedlinePlus lists these signs of dehydration:

• dry mouth and increased thirst
• urinating less often, or dark yellow urine
• eyes that look sunken
• skin that doesn't bounce back when you pinch it

Keep a water bottle nearby and sip through the day. If you can't keep fluids down, that's a reason to call.

Eating enough when you're not hungry

A smaller appetite is expected. But eating too little, especially too little protein, can leave you tired and weak. The Academy of Nutrition and Dietetics says protein should be a priority on these medicines, because it helps preserve lean body mass.

Try a few bites of protein at each meal, even if the meal is small. Our guide to protein on a GLP-1 has easy options.

When to call your prescriber or get help

MedlinePlus lists these as serious symptoms for semaglutide injection. Call your doctor right away or get emergency care if you have:

• ongoing pain that starts in the upper left or middle of your stomach and may spread to your back, with or without vomiting
• rash, itching, fainting or dizziness, swelling of your face, eyes, mouth, tongue or throat, or trouble breathing or swallowing
• less urination, or swelling in your legs, ankles or feet
• vision changes
• pain in your upper stomach, yellow skin or eyes, fever, or clay-colored stools
• a fast or pounding heartbeat
• severe stomach or bowel problems

For nausea and vomiting in general, MedlinePlus says to contact your provider right away if you've been vomiting for more than 24 hours, can't keep fluids down for 12 hours or more, haven't urinated for 8 or more hours, or have vomited 3 or more times in a day. Call 911 if you see blood or dark, coffee-colored material in your vomit.

MedlinePlus also notes that semaglutide can cause other side effects not on these lists, and says to call your doctor if you have any unusual problems. If you have a serious side effect, you or your doctor can report it to the FDA's MedWatch program online at fda.gov/Safety/MedWatch or by phone at 1-800-332-1088.

The Wegovy label also flags pancreatitis, gallbladder problems and, for people with type 2 diabetes who take insulin or a sulfonylurea, a higher risk of low blood sugar.

This guide is general information, not medical advice. Talk with your prescriber about side effects, and don't start, stop or change any medicine on your own.

A calmer first month

Side effects are easier to manage when you keep track of what helps. Olive checks in with you every day and notices what's keeping your body stuck.

If steady habits haven't moved stubborn weight, Olive's Protocol is one option to look into. Prescriptions are only written after a medical consultation with a licensed provider. Not everyone qualifies.

See how Olive works →