What you’ll learn:
- Mounjaro® works by mimicking two hormones that affect appetite and digestion, which is why many of its side effects, like nausea and bloating, start in the gut.
- The most common side effects—nausea, diarrhea, and fatigue—tend to show up early or after dose increases, but usually fade as your body adjusts.
- You can manage most side effects by eating smaller meals, staying hydrated, and following your provider’s titration plan to increase your dose slowly.
You’ve probably heard of Mounjaro®—it’s quickly become one of the most talked-about options for (off-label) weight loss. Like Ozempic®, it’s a once-weekly injectable medication that’s FDA-approved to treat type 2 diabetes but has also helped many people lose weight.
The active ingredient in Mounjaro® is tirzepatide, which mimics two hormones—GLP-1 and GIP—that work together to lower your appetite, slow digestion, and help regulate blood sugar. These changes can make a big difference in how your body processes food and how energized you feel throughout the day.
That said, as your body gets used to the medication, some side effects are common, especially in the first few weeks. The ones most frequently called out by people taking Mounjaro® are digestive, like nausea, bloating, or changes in bathroom habits. Some people also notice fatigue, headaches, or mild irritation at the injection site.
You might feel these again when your dose goes up—but that’s expected. Your doctor will slowly increase your dose (a process called titration) to help ease the transition and reduce side effects.
Most symptoms tend to fade as your body adjusts, and many can be managed with a few smart tweaks, like changing how you eat, staying hydrated, and checking in with your provider.
Up next: we’ll walk you through the most common side effects of Mounjaro®, how to manage them, and when a symptom might be a sign to call your doctor. Knowing what to expect can help you stay confident and in control.
Understanding why Mounjaro® causes side effects
When you take Mounjaro®, it works by mimicking the effects of two hormones that regulate blood sugar, appetite, and digestion. Here’s why these actions can cause issues:
- In the digestive system, Mounjaro® slows gastric emptying, which means food stays in your stomach longer. This helps prevent sharp blood sugar spikes after meals and also promotes fullness that can curb eating. But the effects on your digestive system can also cause nausea, vomiting, diarrhea, and stomach pain as food lingers in your stomach.
- In the brain, Mounjaro® acts on appetite centers to reduce hunger and food cravings. It helps you feel full sooner and more satisfied with smaller meals, making it easier to eat less without feeling like you’re restricting yourself. But, eating less may also lead to fatigue since your body is receiving less fuel.
When are the side effects of Mounjaro most likely to occur?
Side effects from Mounjaro® are most likely to show up during the first few weeks of treatment or shortly after your dose increases. These adjustment periods are when people typically notice symptoms like nausea, bloating, fatigue, or changes in bowel habits.
These reactions are typically mild to moderate and usually temporary and can be managed with better eating habits and slow dose changes.
Your doctor will have you begin at the lowest dose, 2.5 mg, once weekly for the first four weeks. If you’re adjusting well with the starting dose, then you’ll usually increase to 5 mg. This dose escalation continues as needed through 7.5 mg, 10 mg, 12.5 mg, and up to a maximum of 15 mg. Some people may not need to continue beyond the lower doses to see results. Learn more about finding the right dose of Mounjaro®.
Mounjaro®: Most common side effects and symptoms by dose
Here’s a closer look at some of the most common side effects by dose and practical tips to help you navigate them comfortably. Again, digestive side effects are the most frequently reported by people taking Mounjaro®.
Here’s what you might experience based on clinical trials:
| Symptom | Mounjaro® 5 mg | Mounjaro® 10 mg | Mounjaro® 15 mg | What can help |
|---|---|---|---|---|
| Nausea | 12% | 15% | 18% | Try eating smaller, more frequent meals instead of large portions. Ginger tea, clear broths, and light snacks like crackers can help soothe your stomach. |
| Diarrhea | 12% | 13% | 17% | Focus on hydration and electrolyte balance. Avoid high-fat, fried, or dairy-heavy foods. Stick to gentle meals like plain rice, applesauce, or oatmeal until symptoms ease. |
| Vomiting | 5% | 5% | 9% | Stay hydrated with small sips of water or ice chips. Eat bland, easy-to-digest foods like toast or bananas. If vomiting is frequent or doesn’t improve, speak with your provider about adjusting your dose. |
| Constipation | 6% | 6% | 7% | Increase your fiber intake gradually with fruits, veggies, or whole grains. Drink plenty of water and stay active. A gentle over-the-counter stool softener can help if needed. |
| Dyspepsia (indigestion) | 8% | 8% | 5% | Try eating more slowly, avoiding rich or acidic foods, and elevating your head while resting. Light walks after meals may also help. |
| Stomach pain | 6% | 5% | 5% | Eat smaller meals, avoid carbonated drinks, and use a heating pad if needed. Persistent pain should be discussed with your provider. |
Mounjaro®: Injection site reactions
Mounjaro® is available as a prefilled injection pen that you use once a week. The injection can be given in the thigh, abdomen, or upper arm, and like many injectable medications, it may cause mild skin reactions at the injection site. About 3% to 6% of people using Mounjaro® experience some kind of reaction at the injection site. These side effects are usually mild and clear up within a few days.
Possible injection site reactions include:
- Mild pain, redness, or swelling
- Itching, small lumps, or general skin irritation
- Occasional bruising or rash, especially if injected in the same spot repeatedly
Tips to reduce injection discomfort
- Rotate your injection sites: Switch between the abdomen, thigh, and upper arm to avoid irritating the same spot.
- Clean the skin properly: Use an alcohol swab and let it dry fully before injecting to help reduce stinging.
- Avoid problem areas: Don’t inject into scarred, bruised, or irritated skin.
- Let the medication warm up: If it’s been in the fridge, allow it to sit at room temperature for 15–30 minutes before use.
- Follow the instructions: Make sure you use the pen exactly as directed to avoid any errors.
- Apply light pressure afterward: A cotton ball can help with any minor redness or bleeding.
If you notice signs of infection like heat, pus, or worsening pain, or if injection reactions don’t improve, contact your healthcare provider.
Are there side effects of stopping Mounjaro®?
Mounjaro® is designed to support long-term weight loss and blood sugar control. Stopping it without a solid plan can lead to changes in your body that may make it harder to maintain the progress you’ve made. Any decision to pause or stop treatment should always be made with your healthcare provider’s guidance.
Here’s what might happen if you discontinue Mounjaro®:
- Increased hunger: Mounjaro® helps reduce appetite, so once you stop, it’s normal for hunger cues and cravings to become more noticeable again.
- Some weight regain is possible: Without the appetite-suppressing and metabolic support of Mounjaro®, it’s common to regain some of the weight that was lost.
- Tapering may ease the transition: In some cases, your provider might recommend gradually lowering your dose to help your body adjust more smoothly.
- Healthy habits are key: Maintaining consistent routines around exercise, balanced nutrition, sleep, and stress management can go a long way in helping you hold onto your results. Tools that offer structure and support, like Noom, can also help you stay on track.
Before making any changes to your medication, speak with your healthcare provider. They can help you come up with a personalized plan that aligns with your long-term health and weight goals—whether that means continuing Mounjaro®, stopping gradually, or transitioning to a different strategy.
Are there any different side effects in females?
Mounjaro® doesn’t have any official side effects that are unique to women, but hormone fluctuations and the effects of weight loss can influence how certain symptoms appear or feel. Here are a few things to be aware of:
- Polycystic ovarian syndrome (PCOS) and menstrual changes: Mounjaro® may help regulate menstrual cycles by improving insulin resistance and supporting weight loss, two major factors involved in PCOS. Some people have also reported irregular periods or spotting, which may also be linked to hormone shifts caused by weight loss.
- Fertility and birth control: As ovulation becomes more regular with weight loss, fertility may increase. Because Mounjaro® isn’t safe during pregnancy or while trying to conceive, it’s important to use effective birth control while taking it. If you’re planning to conceive, you should stop using Mounjaro® at least two months beforehand.
- Hair thinning: Some people experience hair loss while taking Mounjaro®, which can be more noticeable in those already dealing with PCOS-related alopecia or menopause-related hair changes.
As always, talk to your healthcare provider if you notice any changes or have questions about how Mounjaro® might affect your reproductive or hormonal health.
Mounjaro®: Safety and warnings
While rare, Mounjaro® may cause serious side effects in some people. Seek immediate medical attention if you experience signs of any of the following:
- Pancreatitis: Watch for severe stomach pain that may spread to your back, especially if it’s accompanied by persistent nausea or vomiting.
- Gallbladder problems: Symptoms may include upper abdominal pain, fever, yellowing of the skin or eyes (jaundice), or unusually light-colored stools.
- Kidney issues: Signs include swelling in the legs or ankles, reduced urination, fatigue, or difficulty breathing, particularly after vomiting or dehydration.
- Low blood sugar (hypoglycemia): This is more likely if you’re also taking insulin or sulfonylureas. Look out for shakiness, dizziness, confusion, sweating, blurred vision, or a fast heartbeat.
- Vision changes: Sudden shifts in eyesight, especially in people with type 2 diabetes, should be evaluated right away.
- Allergic reactions: Seek emergency care if you experience swelling of the face, lips, tongue, or throat; difficulty breathing; a rash; or severe itching.
Boxed warning: Thyroid C-cell tumors
Mounjaro® carries a boxed warning due to a potential risk of thyroid C-cell tumors. This was seen in animal studies, though it’s not yet clear if the same risk applies to humans.
We’re still learning about the long-term effects of Mounjaro®. If you notice anything unusual or concerning, don’t wait—reach out to your healthcare provider. They’re there to support your health and guide you safely through treatment.
Learn more about its full list of side effects on the Mounjaro® safety page.
Who shouldn’t take Mounjaro®
Mounjaro® isn’t suitable for everyone, especially if certain medical conditions are present that could increase the risk of complications. You should not use Mounjaro® if:
- You or a close family member has a history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN 2)
- You’re allergic to Mounjaro® or any of its ingredients
- You’re pregnant, trying to become pregnant, or breastfeeding
Talk to your doctor before starting Mounjaro® if:
- You’ve ever had pancreatitis.
- You have a serious digestive condition, such as gastroparesis, which slows stomach emptying. Mounjaro® may worsen symptoms like nausea, bloating, or stomach discomfort in these cases.
For the most up-to-date safety information, consult your healthcare provider or visit the official Mounjaro® website.
Mounjaro® side effects vs. other GLP-1 medications
All GLP-1 medications can come with gastrointestinal side effects like nausea, vomiting, and diarrhea, especially when you first start the medication or if you’ve recently increased your dose. But, each GLP-1 medication may have slightly different effects. Tirzepatide (Mounjaro® /Zepbound®) and dulaglutide (Trulicity®) have generally been shown to result in lower rates of nausea and constipation compared to semaglutide (Wegovy®/Ozempic®) and liraglutide (Saxenda®/Victoza®).
Here’s how these medications compare at the maximum dose for each:
| Medication (dose) | Nausea | Vomiting | Diarrhea | Constipation | Dyspepsia (indigestion) |
|---|---|---|---|---|---|
| Tirzepatide (15 mg) (Mounjaro®) | 18% | 9% | 17% | 7% | 5% |
| Semaglutide (1 mg) (Ozempic®) | 20% | 9% | 9% | 3% | Not reported |
| Semaglutide (2.4 mg) (Wegovy®) | 44% | 24% | 30% | 24% | 9% |
| Liraglutide (1.8 mg) (Victoza®) | 20% | 9% | 12% | 5% | 7% |
| Liraglutide (3 mg) (Saxenda®) | 39% | 15% | 21% | 19% | 9% |
| Dulaglutide (4.5 mg) (Trulicity®) | 16% | 9% | 10% | Not reported | 2% |
Mounjaro® side effects: Frequently asked questions
Does Mounjaro® have fewer side effects than Ozempic®?
At the maximum dose, Mounjaro® (tirzepatide) tends to cause less nausea and vomiting than the 1 mg dose of semaglutide (Ozempic®). People taking Mounjaro® could have higher rates of diarrhea and constipation.
People taking the maximum dose of semaglutide (2.4 mg), found in Wegovy®, had higher rates of nausea, vomiting, diarrhea, and constipation than with Mounjaro®.
How long do the side effects of Mounjaro® last?
Most mild side effects—like nausea, diarrhea, or fatigue—last a few days to a few weeks, especially during the first few weeks of treatment or after a dose increase. Rarely, more serious effects may persist longer and require medical guidance.
Do Mounjaro® and Zepbound® have the same side effects?
Yes—because both use the same active drug in the same, tirzepatide, in the same doses, they share the same side effects: gastrointestinal symptoms, fatigue, injection-site reactions, and a boxed warning for thyroid C-cell tumors.
Does Mounjaro® cause hair loss?
Hair loss isn’t a direct side effect, but rapid weight loss can trigger what’s called telogen effluvium, a temporary shedding that affects around 4 to 6% of people. Hair thinning usually resolves within a few months.
Does Mounjaro® make you tired?
Yes, fatigue is a reported side effect—often tied to less food intake, dehydration, or dose adjustment—but it typically improves after a few days to weeks.
Managing Mounjaro® side effects with support
Understanding what to expect—and how to respond to the side effects of Mounjaro® can make a big difference in how long you stick with treatment. Most side effects, especially digestive ones like nausea or bloating, are part of your body adjusting to the changes in appetite and digestion caused by tirzepatide. With a gradual dose increase and supportive habits like staying hydrated and eating smaller meals, many people find that these symptoms become easier to manage or fade over time.
If you’re considering Mounjaro® or are already on it, remember that everyone’s experience is a little different. While some people breeze through side effects, others may need a bit more support. What matters most is making sure your treatment plan is helping you move toward your health goals safely and sustainably.
If you want more personalized guidance, see if you qualify for Noom Med. You’ll be connected with a clinician who can assess your goals, find the right medication for you, and prescribe it if needed. They’ll help design a weight loss plan to follow while taking a GLP-1 medication. Plus, you’ll get access to all of Noom’s behavior tools and trackers to help you develop a healthy lifestyle you can stick with.
Note: Mounjaro®, Trulicity®, Ozempic®, and Victoza® are not FDA-approved for treating obesity or weight loss.
