Guide · Timeline
Your first week on a GLP-1: what to expect and what helps
The first week is mostly about getting used to a new rhythm: smaller appetite, a shot day to remember, and a stomach that may need some patience. Here’s what’s common, a simple plan for the week, and when to call.
The short answer
Expect to feel full sooner and want less food. Stomach side effects are common in the first weeks and after a dose increase, and they usually ease on a stable dose.1,3 Eat small meals every few hours, put protein first, and sip fluids all day.1 Tell your other healthcare providers you’ve started, and know the signs that mean you should call.2
What’s common in the first week
GLP-1 medicines slow how quickly your stomach empties and act on appetite signals in the brain.1 For most people that shows up as feeling satisfied on smaller portions, sometimes surprisingly early in the week. Some people feel very little at first. Both are normal.
Side effects are relatively common but usually not severe. They’re most likely in the first weeks and with each dose increase, and they tend to get less frequent and milder on a stable dose.1 Across the large trials, the stomach-related ones were reported in these ranges:
- Nausea
- 25% to 44% of people1
- Diarrhea
- 19% to 30%
- Constipation
- 17% to 24%
- Vomiting
- 8% to 24%
- Stomach pain
- 9% to 20%
Ranges are from the trials summarized in the 2025 joint nutrition advisory.1 In SURMOUNT-1, most stomach side effects of tirzepatide were mild to moderate and happened mainly while the dose was being increased.3
If nausea is the hard part, our guide to what helps on GLP-1 nausea days goes deeper.
A simple plan for week one
You don’t need a new diet this week. You need a few small habits that make the adjustment easier.1
Pick your shot day, and set a reminder
Choose a day and time that fits your week, and set a reminder so it doesn’t depend on memory.
Eat small, and eat regularly
A small breakfast, then something small every 3 to 4 hours. Going hours without food can make nausea worse.
Protein first
When you’re full fast, eat the protein on your plate before the rest. See protein on low-appetite days.
Sip fluids through the day
Small, steady sips. Nausea, vomiting, or diarrhea can dehydrate you faster than you’d expect.
Go easy on greasy food and big meals
Fatty foods, and high-fiber foods in the first few days, can make symptoms worse. Vomiting is more likely after large meals.
Keep alcohol minimal
It can make nausea and heartburn worse while you adjust.
Start a weigh-in habit, gently
Weigh in at the same time of day, and judge progress by the weekly trend, not one morning.
Keep a question list
Write questions down as they come up, so your next appointment covers what matters to you.
Week one with Aven
Aven texts you through the first week: setting up your shot-day reminder, checking in the day after, and keeping track of what helped, so week two starts easier.
Aven- Thursday 6:30 PM
- First shot tonight. Kind of nervous
- That’s really normal. Want me to make Thursday at 7 your weekly shot-day reminder? I’ll check in tomorrow morning too.
- Yes to both
- Friday 8:15 AM
- Morning! How do you feel? Today, try a small breakfast with some protein, like eggs or Greek yogurt, and keep water nearby.
- A little queasy but okay. Not hungry at all
- That’s common this early. Small is fine. I’ll text at 11:30 so lunch doesn’t get skipped.
Who to tell, and what to mention
The Zepbound® Medication Guide lists a few things to raise with your healthcare providers. Other GLP-1 medicines have their own Medication Guide; check yours.2
- Any upcoming surgery or procedure with anesthesia or deep sedation. Tell every provider involved that you take a GLP-1.2
- Birth control pills. For tirzepatide, the label says they may not work as well for a while after you start or increase your dose. Ask whether to use another method.2
- Insulin or a sulfonylurea. Taking these with a GLP-1 can raise the chance of low blood sugar.2
- Every other medicine and supplement you take, including over-the-counter ones.
When to call your prescriber, or 911
Call your prescriber
- You can’t keep fluids down, or vomiting or diarrhea won’t stop. Losing fluids can lead to kidney problems.2
- Stomach problems that are severe or don’t go away.2
- Right away: severe stomach pain that won’t go away, with or without vomiting, sometimes reaching your back.2
Call 911
- Swelling of your face, lips, tongue, or throat; trouble breathing or swallowing; fainting; or a very rapid heartbeat. These can be signs of a serious allergic reaction.2
Not a complete list. Your medicine comes with its own Medication Guide; read it before your first shot.
What Aven does, and doesn’t do
Aven does
- Set your shot-day reminder in plain words
- Check in the day after and follow up
- Help with small meals, protein, and fluids
- Keep your question list for your next visit
Aven doesn’t
- Give dose amounts, schedules, or changes
- Diagnose anything or replace your care team
- Wait in an emergency: Aven tells you to call 911 right away
Questions people ask
What should I expect in my first week on a GLP-1?
Most people notice they feel full sooner and want less food. Stomach side effects such as nausea, diarrhea, or constipation are common, and they are most likely in the first weeks and after a dose increase. They tend to ease with time on a stable dose.1
What should I eat in the first week on a GLP-1?
Small meals more often, starting with a small breakfast and then something small every 3 to 4 hours, with fluids. Eat the protein on your plate first. In the first few days, go easy on fatty foods and on high-fiber foods, which can make stomach symptoms worse.1
Is it normal to not feel hungry on a GLP-1?
Yes. GLP-1 medicines slow how quickly your stomach empties and act on appetite signals, so feeling less hungry is expected.1 Low appetite still means you need enough food, fluid, and protein, so small, regular meals matter more than usual. If you can barely eat or drink, call your prescriber.
Who should I tell that I started a GLP-1?
All of your healthcare providers, especially before surgery or any procedure that uses anesthesia or deep sedation. The Zepbound® Medication Guide also asks you to tell your provider if you use birth control pills or take insulin or a sulfonylurea.2
Sources
- Mozaffarian D, Agarwal M, Aggarwal M, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Am J Clin Nutr. 2025;122(1):344-367. doi:10.1016/j.ajcnut.2025.04.023
- Zepbound® (tirzepatide) Prescribing Information and Medication Guide. Eli Lilly and Company; revised August 2026. DailyMed
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216. doi:10.1056/NEJMoa2206038
This guide is general education, not medical advice. Research is cited as background on GLP-1 treatment, not as evidence about Aven. Aven is not affiliated with Novo Nordisk, Eli Lilly, or any drug manufacturer.