What to Expect on GLP-1s: Typical Side Effects and Symptoms

If you’re starting a GLP-1 medication or have recently begun treatment, you’re probably wondering what to expect. Maybe you’ve heard stories about intense nausea or you’re currently having digestive issues and wondering if what you’re feeling is normal. Here’s the reality: many people do experience side effects, particularly in the early weeks, and while these symptoms are typically temporary, they can range from mildly uncomfortable to genuinely disruptive to your daily life. (1) Understanding what’s normal and what’s not can help you navigate this adjustment period with confidence. Here’s some of the most common GLP-1 side effects and symptoms, what to expect, and why they happen.

Nausea and Vomiting

Nausea is one of the most common side effects people experience when starting a GLP-1 medication. (1) You might feel queasy, lose your appetite, or feel uncomfortably full after eating much less than usual. Some people occasionally experience vomiting, particularly early in treatment as the body adjusts to the medication. (6)

The intensity of nausea is usually highest during the beginning of treatment or when the dose increases. Many people find that eating smaller portions and avoiding heavy, high-fat meals helps reduce discomfort during this adjustment period. (6)

“Feeling nauseous and full can be a really uncomfortable experience. Only you can decide what feels tolerable, but it’s important to know that these side effects are pretty short-lived,” says Stephanie Saletta, a dietitian with MyFitnessPal. “Your body typically adapts after you’re done escalating your dose.” (6)

While these side effects often resolve with time, that doesn’t make them any less real or uncomfortable in the moment. Some people find the nausea manageable with dietary adjustments; others may need their healthcare provider to slow down the dose escalation or explore additional support strategies.

Why This Happens

GLP-1 medications slow gastric emptying. (7) Translation? Food stays in your stomach longer before moving into your intestines. This delayed emptying is part of how these medications reduce appetite and support weight management, but it can cause that over-full, nauseous feeling as your body adjusts to the change.

Constipation

Constipation is another very common side effect, affecting a significant number of people taking GLP-1s. (1) You might notice less frequent bowel movements or difficulty passing stools.

This digestive change is typically most noticeable in the first month but can persist for longer. (8) Staying well-hydrated and maintaining adequate fiber intake can help manage constipation. (6) Some people find that their bowel habits never quite return to their pre-medication pattern, but they settle into a new, manageable routine.

Why This Happens

Because GLP-1 medications slow digestion overall, food moves through your entire digestive system more slowly. (10) This slower transit time naturally leads to less frequent bowel movements and can lead to constipation.

Diarrhea

While constipation is more common, some people experience the opposite. Diarrhea or loose stools can happen, especially if you’ve made significant changes to your diet or are eating very differently than before starting medication. (1)

For some people, it’s an initial adjustment that resolves within a few weeks. For others, it may be intermittent. If diarrhea is persistent or severe, it’s worth discussing with your healthcare provider, and staying hydrated becomes even more important.

Why This Happens

Diarrhea on GLP-1s may be related to individual digestive responses to the medication, changes in your gut, or shifts in what and how much you’re eating. Everyone’s digestive system responds differently to these metabolic changes.

Reduced Food Noise

One of the most celebrated effects of GLP-1 medications isn’t uncomfortable at all. It’s the reduction in “food noise.” (10) Food noise refers to the constant mental chatter about food: thinking about your next meal, fighting cravings, planning what you’ll eat, feeling preoccupied with food throughout the day.

Many people on GLP-1s describe a dramatic quieting of these thoughts. You might notice that you’re simply not thinking about food as much, that cravings feel less urgent, or that you can make food decisions without the same mental struggle. (10)

“Some people describe the reduction in food noise as life-changing,” says Saletta. “They finally feel like they can focus on things other than their next meal.”

You might also notice that you feel genuinely satisfied with smaller portions, that you can stop eating when you’re comfortably full, or that foods you once found irresistible simply don’t have the same pull. 

Why This Happens

GLP-1 medications work in your brain as well as your gut. (3) They affect the reward pathways and appetite-regulation centers that drive food-seeking behavior and cravings. This brain effect is what creates that quieter mental space around food decisions.

Better Blood Sugar Control

If you have type 2 diabetes or prediabetes, you might notice improvements in your blood sugar levels. (3) Your fasting glucose may decrease, your post-meal blood sugar spikes may be less dramatic, and your A1C may improve over time.

These blood sugar improvements can contribute to more stable energy throughout the day. (11) Some people notice they don’t experience the same afternoon energy crashes or the “hangry” feelings they used to get between meals.

Even if you don’t have diabetes, more stable blood sugar can contribute to reduced cravings and more consistent energy levels.

Why This Happens

GLP-1 medications can improve blood sugar control in multiple ways. (3) They enhance insulin secretion from your pancreas when blood sugar rises, suppress glucagon (a hormone that raises blood sugar), and slow the absorption of glucose from your meals due to delayed gastric emptying.

Energy and Fatigue

Low energy and more fatigue can happen on GLP-1, due to reduced calorie and nutrient intake. (12)(6) You may feel physically fatigued, need more sleep, or notice your workouts feel harder than they were before.

This tiredness is usually the result of under-fueling from eating less overall. Experts recommend eating nutrient-dense foods like fruits, vegetables, whole grains, and lean proteins to ensure adequate nutrient intake. (1) If persistent fatigue continues, it’s worth discussing with your healthcare provider. 

Why This Happens

This fatigue can happen for several reasons. You may be eating significantly fewer calories than your body is accustomed to burning. Your body is also adjusting to the medication itself and the metabolic changes it creates. Additionally, shifts in your blood sugar patterns (even positive ones) can temporarily affect energy levels as your body adapts.

When Side Effects Need Medical Attention

While many GLP-1 side effects are typical and temporary, certain symptoms require prompt medical attention. It’s also worth noting that ‘manageable’ is subjective. If side effects are significantly impacting your quality of life—even if they don’t fall into the severe categories below—that’s worth discussing with your provider. You shouldn’t have to white-knuckle through weeks of persistent discomfort.

Call your health care provider if you experience any of the following: (5)

• Severe abdominal pain that doesn’t improve or is located in your upper abdomen radiating to your back (potential sign of pancreatitis)
• Persistent vomiting that prevents you from keeping down food or fluids for more than 24 hours
• Signs of severe dehydration (dark urine, extreme dizziness, rapid heartbeat, inability to urinate)
• Allergic reactions (difficulty breathing, severe rash, swelling of face or throat)
• Vision changes or signs of diabetic retinopathy worsening

Trust your instincts. If something feels seriously wrong or different from the typical side effects described here, contact your healthcare provider. It’s always better to check in than to wait and worry.

How Long Do Side Effects Last?

For many people, the timeline looks something like this:

Weeks 1 to 4: Side effects are typically most intense during this period, particularly nausea, reduced appetite, and digestive changes. This is your body’s initial adjustment phase. (4)

Weeks 4 to 8: Digestive symptoms can improve for some people. You may still notice reduced appetite and food noise, but the uncomfortable aspects can lessen considerably. (4)

Beyond 8 weeks: Some people find they’ve adjusted well and experience minimal side effects, though some degree of appetite suppression and slower digestion typically continues (this is part of how the medication works).

It’s important to know that when your dose increases, you may experience a temporary return of side effects. (6) This pattern of adjustment after dose changes is completely normal.

Some people have minimal side effects throughout their treatment, and that’s normal too. Having fewer side effects doesn’t mean the medication isn’t working for you.

Tips for Managing Common Side Effects

A few strategies can help you navigate the adjustment period more comfortably: (6)

• Adjust your eating patterns: Smaller, more frequent meals often feel better than three large meals. Listen to your fullness cues and stop eating when you’re satisfied, even if there’s food left on your plate.
• Stay hydrated: Sipping water throughout the day helps with both nausea and constipation. Some people find that cold or carbonated beverages help settle their stomach.
• Be strategic about food choices: If nausea is an issue, avoiding very greasy or high-fat foods can help. If constipation is a problem, prioritize fiber-rich foods and adequate water intake.
• Communicate with your healthcare provider: If side effects feel unmanageable, your provider may adjust your dosing schedule or suggest additional strategies. Don’t suffer in silence, and never stop your medication without consulting your provider first.

“It’s really important to stay in close communication with your healthcare team,” says Saletta. “They can advise when a mild side effect becomes something to worry about, and even in the case of mild side effects, there are almost always adjustments that can make the experience more tolerable.”

Frequently Asked Questions

Are side effects a sign the medication is working?

Not necessarily. While side effects show that the medication is affecting your system, not everyone experiences side effects of the medication. (13) Effectiveness is better measured by appetite changes, weight trends, and (if applicable) blood sugar improvements.

Will side effects get worse when my dose increases?

You may experience a temporary return of side effects after a dose increase, but they typically resolve more quickly than during your initial start. (6) Many people find that subsequent dose adjustments cause milder symptoms than their first few weeks.

Should I stop taking my GLP-1 if I have nausea?

Nausea is one of the most common side effects and usually improves within a few weeks. (1) Talk to your healthcare provider about strategies to manage it—they may suggest taking your dose at a different time, adjusting your eating patterns, or temporarily staying at your current dose longer before increasing.

Is it normal to not have any side effects?

Yes, everyone’s experience is different. Not everyone reports experiencing side effects on GLP-1 medications. This doesn’t mean the medication isn’t working.

Can I do anything to prevent side effects?

While you can’t prevent them entirely, starting at the lowest dose and increasing gradually (as prescribed) gives your body the best chance to adjust. Following the eating strategies mentioned above from the start may also help minimize discomfort. (6)

The Bottom Line

Starting a GLP-1 medication comes with an adjustment period for most people. While many side effects do improve over time, the experience can range from barely noticeable to genuinely challenging—and both experiences are valid. Nausea, constipation, and other digestive changes are typical in the first few weeks and often improve by the one- to two-month mark. Many people also experience welcome changes like reduced food noise and better blood sugar control. Stay in close contact with your healthcare provider, especially during the first few months, and remember that most side effects don’t require stopping your medication—they just require patience and sometimes a few strategic adjustments. With proper support and realistic expectations, you can navigate this period successfully and work toward your health goals.

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