Just took your first GLP-1 dose? Here’s what to expect

You got the prescription, unboxed it, and took your first dose of a GLP-1. Exciting? Yes! Maybe stressful? Also yes! The first 48 hours on a GLP-1 can make some people anxious, because how those first few days go can be hard to predict. Some people feel nothing, and others might need to stay close to a bathroom or experience other symptoms.

The good news is that the most common side effects are well-documented, so you can know what you're feeling if symptoms arise. And you may also be able to help minimize those side effects through what and how you eat and drink, which can make a difference in how you feel.

You’ll feel a lot of changes during your first month on a GLP-1, but for the first 48 hours, you’re dealing with a brand-new experience. With that in mind, here’s what you can expect after your first GLP-1 shot.

Key Takeaways

• For most people the first 48 hours are uneventful — you may feel nothing at all, or mild nausea, fullness, or fatigue as your body adjusts.

• Side effects, if they show up, are usually mild at the lowest starting dose and tend to ease within days.

• Eat small, bland, protein-forward meals; sip water steadily; try to avoid greasy, spicy foods and alcohol.

• You won’t see weight change in 48 hours — that’s normal and expected; GLP-1s work gradually over weeks.

• Know the few red-flag symptoms that mean you should call your clinician right away.

First, let’s start with how the GLP-1 is supposed to work. A hormone naturally released by the gut when you eat, GLP-1 works to extend feelings of fullness, reduce your appetite, and stabilize your blood sugar after a meal. 

It’s hard to know how you’ll feel during your first day on Ozempic, Wegovy, Zepbound, or other GLP-1 medication. “It’s very person dependent,” says Dr. Sabina Kobylinski-Tognazzini, D.O., a clinician through Weight Watchers Med+. You may not feel anything at all — or you might experience nausea or a lack of interest in dinner. These are all perfectly normal after you take your starting dose.

As far as the GLP-1’s benefits, “most people feel a reduction in appetite right with the very first injection,” says Dr. Robert Kushner, M.D., professor of medicine and medical education at Northwestern University Feinberg School of Medicine in Chicago. “That varies from person to person, but it's often, ‘I just don't have an appetite to eat,’ or ‘I'm less hungry than I normally am’.” That said, if you don’t feel this, that’s okay. “Some people don't feel anything right away,” says Kobylinski-Tognazzini. “It really depends.” 

The same goes for most side effects. It’s important to prepare for and expect you’ll experience one or more GI side effects, the most common of which are nausea, vomiting, diarrhea, and constipation. “That doesn't mean you're going to get them,” says Kobylinski-Tognazzini. But it’s better than the alternative — which is assuming you won’t have any side effects and then being surprised by them, especially considering there are lifestyle changes you can make and even medications that may help if the side effects are significant.

While nausea and vomiting get top billing, any GI distress can be fair game, too. You might feel bloated or a sense of fullness, or find that you’re burping more than usual, according to Kobylinski-Tognazzini. But again, this is typical — and usually nothing to be worried about. That’s why you’re starting on the lowest dose: It’s to allow your body to adjust slowly, as the higher doses can be associated with more side effects.

Again, there’s no guarantee that you’ll feel anything from your first shot, be it the benefits of a GLP-1 (like less food noise) or downsides like any side effects. The timeline can vary, too. “Some people can feel things right away, and for some people it takes a while,” says Kobylinski-Tognazzini. 

As an example, though, here’s what the next 48 hours after your first dose might look like:

• First few hours: You probably won’t feel anything just yet.

• Your first night: You may have some nausea or a disinterest in eating.

• The next morning: Your appetite might feel lower — as if you just don’t feel like eating.

• The second day: If you have any side effects, they might be fading; at the same time, the feelings of fullness and lack of appetite might become more noticeable.

Since you won’t exactly know how you’ll feel on a new medication, you may want to plan to lay low during these days if possible, rather than starting it the day before a big presentation at work or a long travel day. “I always want people to prepare for or have an expectation that you're going to have a side effect — that's how you use caution,” says Kushner. “You don't want to get caught off guard when you’re out in a restaurant or with other people and find that you really don’t feel well.”

Even if the effects of your GLP-1 are subtle — if you feel anything at all — it’s still a good time to focus on what and how you eat. “The first 48 hours are probably one of the most important when it comes to making dietary changes in order to reduce the GI side effects of the medication,” says Kushner.

Weight Watchers can make it even easier by helping you implement these changes in your diet and track your protein intake, hydration, and meals through the WW app — all so you can optimize your diet while you’re starting your GLP-1. Our Med+ Program not only gives members access to GLP-1s, but a whole lifestyle program designed to help you track your progress, prioritize key nutrients, and manage side effects. In fact, 73% of surveyed Med+ members given the GLP-1 Success program say that Med+ helps minimize weight-loss medication side effects.*

With that in mind, here’s what you can do to manage GLP-1 side effects and feel confident and healthy as you make this transition.

Do: Stay hydrated

Hydration is critical — and it’s easy to fall short if you’re not consciously trying to get enough fluids. Kobylinski-Tognazzini recommends drinking at least 60 ounces a day (which is roughly eight glasses' worth). That’s because some of the changes that accompany GLP-1s, even from a first dose — like feeling overly full or queasy — can make you less likely to drink water throughout the day. On top of that, some of the side effects, like vomiting and diarrhea, can actually make you lose hydration.

And on the other end of the GI side-effect spectrum is constipation, which is also worsened by dehydration. Instead of trying to chug water, which can trigger nausea or vomiting, try consistently taking small sips throughout the day. Icy or hot beverages, rather than room temperature, tend to be better tolerated when you’re nauseous, so you may want to reach for ice water or tea (bonus if it’s ginger or peppermint tea, which can also help settle the stomach).

Don’t: Skip meals

If you’re not hunting for a snack or going for seconds, that’s normal — and depending on your appetite, you might be tempted to skip meals, even in your first 48 hours on a GLP-1. In fact, “some people will lose their appetite and just not want to eat for three or four days,” says Kobylinski-Tognazzini. That’s a concern since if you do that, you won’t get the nutrients your body needs to function. But on top of that, “if you have an empty stomach, you may have more side effects,” she says. So plan to eat on your usual schedule, but opt for smaller portions — even if you don’t feel particularly hungry. Focusing on nutrient-dense foods helps to get the important nutrition your body needs while adjusting to the medication.

Do: Adjust how you eat

How much you eat is just as important as what you eat, so it’s key to adjust your portion sizes so don’t feel overly full or nauseous. It might be hard to get used to, especially when you’re accustomed to putting a certain amount of food on your plate. “But when you take this medication, it changes how much food you need to feel full,” says Kushner. So if you eat the same amount that you normally do, “you're likely to feel very full and nauseated,” he says.

He also recommends slowing down and checking in with yourself as you eat. “Am I getting full? Should I stop now?” he suggests. That can help you notice and recognize the sensations in your body now that you’re on a GLP-1, which can help keep you from being uncomfortable at the end of a meal.

Don’t: Eat heavy, fried foods

A lower appetite doesn’t mean you can eat a few chips for dinner and call it a day. Instead, your GLP-1 diet should prioritize protein (which can help you maintain muscle even though you’re eating less) and fiber (which can help with some of the side effects, like constipation). A protein shake or a small bowl of oatmeal (with berries, for bonus fiber) are two good bets, according to Kobylinski-Tognazzini.

Steer clear of fatty or greasy foods. Not only do they take over the limited real estate that you want to reserve for more nutrient-dense foods — a big deal when you’re eating less — but they can also worsen side effects. That’s because the GLP-1s slow down gastric emptying, meaning a fried, high-fat meal is more likely to hang out in your digestive system. “The food won't be passing through as fast as it normally does, so you could have backwash, burping, and reflux,” says Kobylinski-Tognazzini.

It’s normal to be excited about starting your GLP-1 journey — and, at the same time, a little anxious. If your appetite is the same, don’t worry that the medication won’t work for you; this is for the long-term. Remember, your first shot is meant to acclimate you to the medication. “You're only starting at the lowest dose. That's on purpose,” says Kushner. “So don't expect maximum effect early on.”

However, you might start to feel fuller and less hungry, which is typical. “Most people do start changing their appetite even at the lowest dose,” Kushner says. And if you have side effects like nausea, vomiting, diarrhea, and constipation — or those that aren’t related to your GI system, like fatigue or redness at the injection side — they’re all standard.

You might not want to bug your doctor over one bout of diarrhea, but it’s worth reaching out if you notice any of the following signs:

• Severe abdominal pain: Bloating is normal, but if you’re doubled-over in pain, that’s concerning. Severe pain may indicate a more serious issue that should be evaluated by a medical professional.

• Persistent vomiting and diarrhea: They can make it hard to get the nutrients you need from meals, and “these can lead to dehydration as well,” she explains.

• Signs of dehydration: Since you might be drinking or keeping down less water than usual, it’s possible to become dehydrated. Early signs are thirst (no surprise) as well as dark-colored urine and dry mouth — which you can take as a cue to drink up. But if you notice mild dizziness, fatigue, and an elevated heart rate, or you’re unable to take in enough liquids for your urine to turn back to pale yellow, call your clinician. More concerning symptoms of profound dehydration such as severe dizziness or fainting, confusion or being unable to stay awake and alert should be addressed by emergency medical services.

• Signs of an allergic reaction: Keep an eye out for clues that you’re having a reaction, which can be hives or swelling on your hands and feet. Swelling of the face and lips, difficulty breathing, and dizziness or fainting should prompt emergency medical evaluation. 

Your Weight Watchers Med+ can provide ongoing support for non-urgent side effects; you can reach your Care Team through messaging in the app. But if you’re experiencing any of these red flags, call 911 or seek immediate care from the nearest hospital emergency room.

The good news is that many GI side effects lessen or even completely resolve over time. So if you experience nausea, burping, or an upset stomach, “they usually improve with proper eating and over time as the body adjusts to the dose,” says Kobylinski-Tognazzini. That’s where creating your routine in the first weeks and months can make a big difference, starting with the necessary changes in your nutrition, physical activity, and overall lifestyle.

And if you’re wondering how long it takes a GLP-1 to work: Its effects are pretty immediate, although it can take a few weeks to see a meaningful change on the scale. But this is just the beginning, and you’ll ladder up the dosage based on your clinician’s guidance until you find the right dose for your body and goals. “Every time you increase the dose, you may also have an increase in side effects,” says Kobylinski-Tognazzini. So even if you’ve been on the medication for weeks, when you increase your dose, it may feel like the first 48 hours all over again.

It can be hard to know what to expect on a GLP-1, since everyone is different. But even so, it’s helpful to go into your first 48 hours after a shot expecting that you’ll experience some GI side effects, and prepare accordingly. Drinking water regularly, eating small, protein-rich meals (even if you don’t feel especially hungry), and avoiding fatty, fried, and greasy meals can help you feel more comfortable. You can top some oatmeal with berries to get fiber, or opt for a protein shake. And remember, this is only the beginning. The lowest dose is meant to help your body adjust so you can stick with it long-term and feel better along the way.