What to expect during your first month on a GLP-1

Embarking on your first month on a GLP-1 may be exciting and mildly anxiety-provoking at the same time. It’s the start of something big, but what could that feel like — in your mind and in your body? 

Whether you’re starting semaglutide, tirzepatide, or orforglipron, you’re likely to soon notice significant shifts in how you experience food, hunger, and fullness. This time can also be the most uncomfortable stretch for many, as your body adjusts to the changes in digestion.

You may be wondering how much stomach upset is normal, what to eat when nothing sounds good, and whether the number on the scale should already be dropping. 

Knowing what you may encounter — and when — can make the process feel a lot less uncertain and it may even help you stick with it. Here’s what could come during your first four weeks on a GLP-1, from the first shot or pill through your first dose increase.

Key takeaways

• Expect appetite changes and potential gastrointestinal (GI) symptoms to kick in within days of your first dose and dose increase. They often let up within about a week.

• Prioritize protein, fiber, and water at every meal to preserve your energy level, muscle mass, and digestive health.

• Eat smaller, more frequent meals with less fat and sugar to minimize stomach upset, and work with your clinician to address any troublesome side effects.

GLP-1 medications mimic the naturally occurring hormone called glucagon-like peptide-1. They activate GLP-1 hormone receptors in both the brain and gut to slow the emptying of the stomach, increase feelings of fullness, and reduce both physical and mental appetite for food. 

Your clinician will generally have you begin with a low starter dose of the medication for the first four weeks and gradually increase the dose over the next several months. That gives the body time to get used to the changes and can help limit GI side effects. GI symptoms tend to be most noticeable early on after the first dose and then return after a dose increase, improving as your body adapts.

You can think of month one as an adjustment period and a time for building habits that will support you over the longer term. 

“The first month is less about losing weight than about learning how your body responds to the medication,” says Dr. Yen-Yi Juo, M.D., a bariatric surgeon and obesity medicine physician at Legacy Good Samaritan Medical Center in Portland, Oregon. Here’s what that might look like:

Week 1 — starting your lowest dose 

The first thing you might sense this week is a difference in how quickly you feel full. “Many begin to notice changes in appetite within the first few days after the first dose,” says Juo. “Some patients describe the feeling as similar to what happens after a large holiday meal: You know you’ve eaten a little more than enough and you simply do not have any interest to eat more.” 

For some people, that sensation crosses the thin line between pleasantly full and uncomfortably full, leading to nausea, vomiting, or diarrhea. These are among the most common side effects reported with GLP-1 medications, and they tend to strike early this first month if they’re going to at all. In one study of tirzepatide, for example, about 10% of participants experienced one of those three GI symptoms in the first four weeks, and few people experienced them for the first time later on at dose escalations if they hadn’t already.

To ease or avoid GI symptoms, focus on staying hydrated and eating smaller meals with less fat. You can start this even before you take your first dose for the best shot at minimizing side effects, says Dr. Edwin Davila, D.O., internal medicine physician, certified sports nutritionist, and National Academy of Sports Medicine advisory board member. 

“Begin looking to prioritize protein in your meals as you reduce the overall volume of food,” says Davila. That way you’ll get the most essential nutrition for preserving muscle and other bodily functions without upsetting your stomach. “For example, if you’re a person who used to eat a traditional breakfast of eggs, bacon, potatoes, and orange juice,” says Davila, “keep the eggs and prepare them without butter.” (Try a light spritz of olive oil spray instead.)

Week 2 — settling in 

During the second week on a GLP-1, some people find that early GI symptoms are easing, or that they’re creeping up mostly around injection day (for those not on a daily pill). For others, new issues like constipation or reflux may arise. This is a good time to start paying attention to patterns, says Davila. When do your symptoms tend to show up? Are they triggered by a certain type of food or drink? Are you leaning heavily on fizzy seltzers? Has your fiber intake spiked or plummeted? Starting a practice of tracking your meals (and any side effects) can help you pick up on potential triggers that could be easily tweaked to relieve indigestion That’s something you can easily do in the WW app with the Weight Watchers Med+ Program.

This week, continue to hit your protein goal but focus on slowly adding fiber to each meal — like apple slices, hummus, or a whole grain oats cereal — and drinking more water in step with that increase. Simply adding a large amount of fiber without enough fluid may make constipation worse, Davila notes. Not sure what your goal for protein and fiber should be? Check in with your clinician. Weight Watchers Med+ makes this simple by putting daily goals for key nutrients front and center in the app. 

Week 3 — appetite really drops 

By now, you may have a much clearer sense of the medication's effect on your appetite. For some people, that means the thought of food becomes less interesting. “As the weeks progress, areas of the brain become more saturated with medication, and it starts to suppress what some people refer to as food noise,” says Davila. 

That can be a welcome change if you've spent years feeling preoccupied with food, but it can also leave you without your usual coping mechanism if you’ve relied on eating as a social or emotional outlet. “Some people feel great, and some people feel disheartened,” says Davila, “so it's incredibly important when you begin your weight-management journey that you’re having discussions with your clinician about mental health.”

To keep up your energy during the “nothing sounds good” phase, try eating smaller amounts of food more frequently instead of three larger meals a day. Keep easy protein sources available — like Greek yogurt, hardboiled eggs, a salmon packet, or a protein bar — and consider soft or liquid foods like smoothies or protein drinks if they seem to go down easier.

Week 4 — your first dose increase 

The first increase in your medication dose may come at the end of this week (after a check-in with your clinician), and with it a potential replay of earlier side effects. 

“When you up your dose, everything that you experienced in week one is possible to experience again,” Davila says. That can include nausea, changes in bowel habits, and a further drop in appetite — though some people report that their symptoms are not as intense as the first go-round. The same strategies that helped at the beginning still apply: Emphasize protein, fiber, and water, and pay attention to foods that seem to trigger your symptoms.

On a GLP-1, the challenge isn’t so much how to eat less as it is how to get enough nutrition to keep your body running smoothly in an amount of food you can comfortably tolerate. That means you shouldn’t skip meals just because you’re not hungry. “The goal is not to see how little you can eat,” cautions Davila, as that could set you up for malnutrition. 

When your appetite is so low that nothing sounds good, reach for your most nutrient-dense foods. Weight Watchers refers to these powerhouses as ZeroPoint foods. Put nutrient-dense protein on your plate early and often: Frequent small portions of eggs, Greek yogurt, cottage cheese, fish, or chicken may be easier to manage than a large protein-heavy meal. Include a fiber source (think: whole wheat toast, berries, your favorite cooked veggie) at every sitting to ward off constipation in concert with plenty of water throughout the day.

If you're experiencing vomiting or significant diarrhea, dehydration becomes a real concern; consider fluids containing electrolytes like coconut water, broth, or a rehydration drink. Liquid meals, like a smoothie with protein powder and ground flaxseed, are an easy-on-the-stomach way to hit all three goals (protein + fiber + fluids).

Nausea

Nausea is one of the most common GI side effects of GLP-1 medications. It often appears early in treatment or after dose increases and frequently improves as the body adjusts. To minimize nausea, eat slowly, choose small portions of easy-to-digest foods (versus spicy, sugary, or greasy), and avoid either lying down or being very active right after meals.

Constipation

Constipation can occur as the medication slows down the movement of food through your digestive tract, and it may stick around longer than other GI symptoms. Drinking more water, getting enough fiber, and exercising can help keep things moving. If constipation is severe, talk with your provider about treating it.

Fatigue

Nutrient deficiencies, dehydration, or simply consuming too few calories overall can lead to low energy on a GLP-1. Make sure you're getting adequate fluids and nutrient-dense food, particularly protein, but mention persistent or significant fatigue to your clinician as well to rule out a more serious cause.

Whatever your initial side effects are (or aren’t), they’re not a sign that the medication is working (or not). Neither is the number of pounds you lose in the first few weeks. Research shows on average people may lose around 2% of their starting body weight by the 4-week mark — essentially a few pounds. 

“Weight loss during the first month on a GLP-1 medication varies widely from person to person,” says Juo. “Early changes on the scale can reflect many things, including eating less, changes in food choices, and shifts in water weight. The outcome we ultimately care about is sustained loss of body fat over time, which usually becomes clearer after the dose has been gradually increased and the medication reaches an effective maintenance level.”

GI side effects after starting or increasing your GLP-1 dose tend to be short-lived, typically clearing up within eight days or less, and they’re not typically a sign that something’s wrong or a reason to stop taking the medication. 

There are two circumstances, however, that warrant calling your doctor rather than trying to just tough it out. “The first is when symptoms are severe enough that you cannot keep fluids down because of persistent nausea or vomiting; dehydration and electrolyte problems can develop quickly and may lead to more serious complications, including kidney injury,” says Juo. “The second is when your symptoms suggest a rare but serious side effect, such as pancreatitis, which typically presents as severe, persistent abdominal pain.” If you’re not able to eat or drink anything, or you have any symptom that’s severe or doesn’t go away, get in touch with your clinician right away or contact emergency medical services.

Building a sustainable routine takes time, and your first month on a GLP-1 provides useful information about what works for your body. It’s the perfect time to establish the habits you want to carry forward for the long term. When you access medication through Weight Watchers Med+, you also get access to the GLP-1 Success Program — a complete nutrition and lifestyle program tailored to life on a GLP-1 — plus seamless tracking, 12,000+ recipes, virtual Workshops with expert Coaches and other members, and ongoing check-ins and messaging with your Clinician and Care Team, all in one app. 

Support like this can have a real impact on your success over the long run: At 12 months, members prescribed a GLP-1 through the Weight Watchers Med+ Program who engaged regularly with the GLP-1 Success Program lost 29.1% more body weight, on average, than those who did not engage in behavioral support.* And 73% of Med+ members given the GLP-1 lifestyle program say that Weight Watchers Med+ helps minimize weight-loss medication side effects.**

The first month on a GLP-1 is a learning curve: You’ll get a better sense of how the medication affects your appetite, digestion, and eating habits, and you’ll start figuring out what foods and routines work for you. Take it week by week, and focus on getting enough protein, fiber, and fluids. If the first few weeks are challenging, don’t assume the medication isn’t right for you — or that you have to tough it out alone. Your clinician can help you manage side effects and decide what adjustments, if any, make sense.