GLP-1 Side Effects: What to Expect and When to Contact Your Clinician

While GLP-1 medications are greatly effective at helping with weight loss, it’s also common for them to come with GLP-1 side effects. In order to keep yourself safe and on a smoother weight loss journey while taking weight loss medications, it’s important to be aware of what these effects are, how to manage them, and when to see a healthcare provider. 

The Most Common Side Effects You Might Experience

Most people taking weight loss medications will experience GLP-1 side effects, particularly in the first few weeks of taking the medication and when your dose increases. The most common side effects affect the digestive system, but they typically improve as your body adjusts to the medication.

The most important thing to know is side effects are normal and not necessarily an indication that the medication is unsafe or ineffective. They can also be manageable through proper use and nutrition, along with open communication with your healthcare provider. 

Nausea and Upset Stomach

A recent study published in the New England Journal of Medicine found that nausea was the most commonly reported of the GLP-1 side effects, with around 44% of users experiencing it during the clinical trial.

The nausea could vary in severity from an upset stomach to feeling like you’re going to vomit, and is typically at its most intense when you first start the medication or in the beginnings of a dosage increase. Do not fret, however. There is a way to manage nausea, which improves after a few weeks as your body gets used to the medication. 

Digestive Issues: Diarrhea and Constipation

As part of its mechanism to control hunger, GLP-1 medications slow down digestion in a way your body may not be used to. As a result, both diarrhea and constipation can occur and varies in significance depending on the individual. 

These are side effects that usually get better the longer you are on the medication, but for some people they persist throughout use. While these effects are uncomfortable, they are not harmful and can be managed through proper nutrition and hydration practices.

Vomiting and Loss of Appetite

Though it’s less common than nausea, vomiting is something that people experience as well. Some people will also lose their appetite completely, get full very quickly, or just become disinterested in food.

One of the main mechanisms that the medication uses to initiate weight loss is by reducing appetite, but there is a difference between appetite reduction and appetite loss. You should contact your clinician if you are vomiting frequently, are unable to keep food down or you are eating a concerningly small amount that results in illness, weakness, or brain fog. 

Other Common Side Effects

Other GLP-1 side effects that are commonly reported include:

• Headaches
• Low energy levels
• Fatigue
• Dizziness or lightheadedness
• Stomach pain or discomfort
• Heartburn or acid reflux

Headaches, fatigue, and dizziness typically occur because you end up eating fewer calories and carbohydrates than normal, which means your body has less energy than it is used to. Dehydration is also common, especially with diarrhea and vomiting.

Stomach pain and heartburn sometimes happen when the medication slows the speed at which food is emptied from the stomach to the gut, and are the most common during dose increases. 

While these effects are mild for most people, if you experience severe stomach pain, fainting, or significant dehydration, it’s a good idea to talk to your prescriber. 

Serious Side Effects to Watch For

Serious side effects that could be hazardous are rare, but are important to identify as they require immediate medical attention. This section is not meant to alarm or worry you if you are taking or considering taking a GLP-1 medication, but simply to keep you informed and safe. 

Pancreatitis Warning Signs

The pancreas contains important enzymes that are meant to help break down food, but when they become blocked by certain medications or conditions like gallstones, it causes the pancreas to become inflamed, swollen, and painful. 

This is a severe pain that doesn’t go away, often radiates to the back, and is accompanied by nausea and vomiting. It typically resolves just fine without becoming chronic if you seek medical treatment promptly. Again, this is a very rare GLP-1 side effect, but can come with serious complications if left untreated. 

Gallbladder Problems

The gallbladder is heavily involved in the digestion of food and, when taking weight loss medications, this drastically alters the way you eat food. This alone can increase the risk of gallstones, but losing weight very quickly can increase risk as well. 

Signs of gallbladder disease include nausea, stomach pain after eating high-fat or greasy foods, and intense pain in the upper right abdomen. If gallstones have developed, then surgery may be needed. However, a very large systematic review showed that a gallbladder condition was only seen in less than 1% of GLP-1 users. 

Low Blood Sugar (Especially If You Have Diabetes)

GLP-1 medications exert their effects on parts of our metabolism that control blood sugar, like its ability to stimulate more insulin, for example. In some uncommon cases, though, it can cause blood sugar to become lower than intended, especially when used alongside other diabetes medications. 

Signs of low blood sugar include very intense hunger, shaking, sweating, confusion, rapid heartbeat, and fainting. People with diabetes who are on insulin or metformin are at a much higher risk of this side effect compared to those taking the medication for weight loss, but quick intervention must be taken nonetheless.

Consuming high-sugar, fast-digesting carbs like fruit juice, soda, or candy can help. Even just a packet of white sugar can help resolve symptoms quickly. If you do have diabetes, make sure you are monitoring your blood sugar regularly to prevent concerning lows while on GLP-1s. 

Allergic Reactions

It’s important to distinguish between injection site reactions which are more localized and very common. However, true allergies to the medication itself are rare and much more serious. Allergic reactions are among the most uncommon GLP-1 side effects, but require emergency medical attention if they occur. 

How to Manage and Reduce Side Effects

The good news about all of this is that the most reported GLP-1 side effects can be made manageable with a mindful diet and other lifestyle changes. Working with a professional like a registered dietitian can give you the individualized counseling you need to minimize discomfort. 

Eating Strategies That Help

Given that many digestive side effects happen because the medication keeps food in the stomach longer than your body is used to, you can help manage symptoms like nausea and heartburn by eating smaller meals more frequently rather than large meals. Eating slowly and stopping when satisfied rather than uncomfortably full can also be helpful. 

Others have also found it helpful to avoid spicy, fatty, or greasy foods which take longer to digest and put more strain on digestion than other foods. Choose bland foods that are easy to chew and digest if you are feeling nausea, try to avoid laying down after eating to avoid acid reflux, and generally listen to your body if it is not tolerating a certain eating pattern properly. 

Staying Hydrated

Dehydration can worsen fatigue, constipation, and light-headedness. So, while on weight loss medication, be sure to sip water throughout the day rather than drinking large amounts at once. 

If you can’t tolerate plain water with nausea, try to have it cold or use calorie-free flavoring (like infusing water with fruit) to encourage more water consumption. If you are experiencing vomiting or diarrhea, it’s even more critical to be mindful of dehydration, as it can quickly become severe with these effects. 

Timing Your Doses Wisely

Taking your medication at the same time of the day every week can help the body adjust more effectively and potentially make GLP-1 side effects more manageable. Some people find it more tolerable to take your weekly dose around a time you can rest, such as before bed, to prevent effects like daytime nausea. 

According to Dr. Devon Allen, Top Nutrition Coaching's medical contributor, the specific hour matters less than choosing one you'll actually keep. "Time of the day is not as important as consistency in timing," she says. "Patients need to determine what time of the day works best for them and their routine, taking into consideration when they are less likely to forget to take the medication or what time of the day is most convenient for them."

From there, your own pattern of side effects can guide the choice. "If they experience GI side effects within the first few hours after taking it, then bedtime administration might be best so that they can sleep through the side effects," Dr. Allen says. "If they experience side effects for a few days following administration, then taking it right before the weekend might be best."

If your healthcare provider has already given you specific instructions on how to time your doses, then be sure to follow those. Never change your dose or dosing schedule without first consulting with your prescriber. 

When to Talk to Your Prescriber About Adjusting Your Dose

If side effects are not improving or becoming hard to manage, you always have the option to ask your prescriber to lower the dose to give your body more time to adjust than the standard four weeks. 

Lowering your dose isn’t an indication of failure or that the medication isn’t working; it’s not about getting to the highest dose. However, if the quality of your daily life is being significantly impacted, such as an inability to eat, sleep, or work properly, don’t hesitate to let your prescriber know.

When to Seek Urgent Care

If you are experiencing any of the following serious symptoms, seek emergency care urgently:

• Prolonged, severe stomach pain, especially one that radiates to your back (potential pancreatitis).
• Shortness of breath, or sudden face, lips, or throat swelling (signs of a severe allergic reaction).
• Unable to keep down liquids or food or confusion, dizziness, or fainting which can be signs of severe dehydration. 

What to Know Before Starting GLP-1 Medications

Have open conversations with your prescriber about what considerations to go over and what treatment is the best for your individual health goals. This is the best way to make the most effective decision for your health. 

Who Shouldn't Take These Medications

Although GLP-1 medications are an exciting new tool to help support weight loss, that doesn’t mean they are a fit for everyone. If you fall under one of these categories, you should talk to your prescriber before exploring GLP-1 options or consider finding an alternative method for weight management that is better for your health:

• Pregnancy or currently trying to become pregnant - Healthy pregnancies often are aligned with weight gain rather than loss and prescription medications always come with their own risks during pregnancy
• History of pancreatitis - The medications increase your risk and a history of the condition makes your pancreas potentially vulnerable to recurrence
• History of thyroid cancer or a family history of thyroid cancers - Genetically, you may be predisposed to these cancers and GLP-1s may increase risk
• Having gastroparesis or other severe digestive issues - Since the weight loss injection causes the stomach to empty more slowly, they may exacerbate these conditions

Given these facts, it’s important to give your physician a complete medical history for them to consider. Even if one of these does apply, there are still alternative weight loss treatments available. 

Medications That May Interact

While your prescriber will go over the specifics of your compatibility with current prescriptions, it’s important to know that this mostly applies to those with diabetes. Medications may interact in a way that is not complementary and can end up doing more harm than good. 

Insulin and certain oral diabetes medications can cause dangerously low blood sugar when used alongside GLP-1 medications, so doses will often need to be adjusted. Also, since GLP-1s affect how quickly food is digested, it can negatively impact how quickly certain oral medications are digested and absorbed. 

That’s why it’s critical to be transparent about any medications or supplements, including herbal and sports supplements, to rule out any potential interactions before continuing. 

Working With a Registered Dietitian While Taking GLP-1 Medications

Pairing GLP-1 medications with proper nutrition can not only make the medication much more effective at supporting healthy weight loss, but can play a big role in minimizing the discomfort of GLP-1 side effects. If this makes sense to you, Top Nutrition Coaching may be able to help. 

How Nutrition Support Helps Manage Side Effects

The most common GLP-1 side effects often affect the digestive system, like nausea, constipation, and diarrhea. Luckily, dietitians can help manage these side effects along with helping you get in the proper nutrition even with a diminished appetite.

As doses increase, weight changes and your experience evolves, a dietitian can also provide ongoing, personalized support to adjust recommendations as you go on your journey. Along with your healthcare provider, nutrition counseling can leave you with the best toolkit for long-term success. 

Getting the Most From Your GLP-1 Treatment

Possibly the most valuable thing about getting nutrition support besides getting the most from your weight loss medication is obtaining the knowledge you need to keep the weight off even after your time taking the GLP-1 is finished.

Many insurance plans cover the cost for those on GLP-1 medications for nutrition counseling like what you find at Top Nutrition Coaching. Get started by taking the online quiz to check insurance coverage and match with a registered dietitian.

Frequently Asked Questions

What are the most common side effects of GLP-1 medications?

The most common side effects of GLP-1 receptor agonist medications (like Ozempic, Wegovy, and Mounjaro) are digestive. They include nausea, vomiting, diarrhea, and constipation.

How long do GLP-1 side effects typically last?

GLP-1 side effects like nausea and vomiting typically peak within 1 to 3 days after an injection and improve within 1 to 8 weeks as your body adjusts.

How can I reduce nausea from GLP-1 medications?

To reduce nausea from GLP-1 medications like Ozempic or Wegovy, eat smaller and more frequent meals, choose bland and low-fat foods, stay hydrated by sipping fluids between meals rather than during them, and talk to your prescriber about slowing your dose increase schedule.

Do GLP-1 side effects get worse when I increase my dose?

Yes, side effects often return or get worse temporarily when you increase your GLP-1 dose.

What are the serious side effects of GLP-1 medications I should watch for?

Serious side effects linked to GLP-1 medications (like Ozempic, Wegovy, Mounjaro, and Zepbound) include severe pancreatitis, gallbladder disease, acute kidney injury from dehydration, severe delayed stomach emptying (gastroparesis), bowel blockages, and severe low blood sugar when combined with other diabetes drugs.

Which GLP-1 medication has the fewest side effects?

No single GLP-1 medication universally has the "least" side effects, as tolerance varies significantly by individual.

Can GLP-1 medications cause pancreatitis or gallbladder problems?

Yes, GLP-1 medications are linked to an increased risk of gallbladder problems like gallstones, but large studies show they do not significantly increase the overall risk of pancreatitis.

How do I know if my GLP-1 side effects are normal or require medical attention?

Normal GLP-1 side effects are usually mild, temporary upper or lower gastrointestinal changes like brief nausea, mild constipation, or loose stool that improve as your body adjusts.

What foods should I avoid while taking GLP-1 medications to minimize side effects?

To minimize side effects like nausea, bloating, and reflux while taking GLP-1 medications, avoid high-fat and fried foods, sugary drinks and sweets, refined carbohydrates, spicy dishes, and alcohol.

Are GLP-1 side effects permanent or do they go away after stopping treatment?

GLP-1 side effects are not permanent. Common gastrointestinal issues like nausea, vomiting, bloating, and diarrhea stop occurring as the medication clears your system and your stomach empties at its normal rate again.