Mounjaro side effects are the adverse reactions reported with Mounjaro (tirzepatide) injection, a once-weekly type 2 diabetes medicine, as listed in its FDA prescribing information.
The most common Mounjaro side effects
Mounjaro is approved for blood sugar control in adults and children 10 and older with type 2 diabetes, and to lower the risk of heart attack, stroke and cardiovascular death in high-risk adults with type 2 diabetes [1]. It is not approved for weight loss. The same medicine, tirzepatide, is sold for weight management as Zepbound [3], and its trial numbers are on Zepbound side effects.
| Reaction | Placebo | 5 mg | 10 mg | 15 mg |
|---|---|---|---|---|
| Nausea | 4% | 12% | 15% | 18% |
| Diarrhea | 9% | 12% | 13% | 17% |
| Decreased appetite | 1% | 5% | 10% | 11% |
| Vomiting | 2% | 5% | 5% | 9% |
| Constipation | 1% | 6% | 6% | 7% |
| Indigestion (dyspepsia) | 3% | 8% | 8% | 5% |
| Abdominal pain | 4% | 6% | 5% | 5% |
Other reactions were less common but more frequent than with placebo: burping (eructation) in 2.5% to 3.3% vs 0.4%, gas (flatulence) in 1.3% to 2.9% vs 0%, reflux (GERD) in 1.7% to 2.5% vs 0.4%, injection site reactions in 3.2% vs 0.4%, and allergic-type reactions in 3.2% vs 1.7% [1]. Average heart rate rose by 2 to 4 beats per minute, and a rise of 15 beats or more occurred in 10% on 15 mg vs 4.3% on placebo [1].
How long side effects last
The Mounjaro label does not give a number of days or weeks. In the SURMOUNT-1 weight trial of tirzepatide, digestive side effects were mostly mild to moderate and happened mainly while the dose was being raised [4]. The label raises the dose in 2.5 mg steps, each after at least 4 weeks [1], which gives time to adjust. Diabetes trial participants stopped because of digestive side effects in 3.0% (5 mg), 5.4% (10 mg) and 6.6% (15 mg) of cases, vs 0.4% on placebo [1].
People call the burping on the label "sulfur burps." The label gives rates for burping but no duration and no treatment, so ask your prescriber if burping or reflux does not settle. No injection site is ranked above another; the label lists the abdomen and thigh, plus the back of the upper arm when someone else gives the shot [1]. Shot steps are on how to use Mounjaro, and eating tips for nausea on what to eat on Mounjaro.
Hair loss, tiredness and muscle
Mounjaro's label lists hair loss among reports after approval, where a rate cannot be measured [1]. Zepbound's weight trials, which used the same medicine, did measure it: 5% on 5 mg, 4% on 10 mg and 5% on 15 mg, vs 1% on placebo [2]. Those trials also found fatigue in 5% to 7% vs 3% on placebo [2]. How long tiredness lasts is not stated; tell your prescriber if it does not improve. Headache, dizziness, body aches, joint pain and feeling cold are not among the most common reactions in Mounjaro's diabetes trial table [1]. Whether hair regrows after stopping is discussed on stopping Mounjaro.
Tirzepatide's label states that it lowers body weight with greater fat loss than lean mass loss [2]. In a SURMOUNT-1 substudy, about 25% of the weight lost was lean mass [5]. Protein and strength training are covered in how to keep muscle on a GLP-1.
Mood, anxiety and depression
No section on depression, anxiety or suicidal thoughts appears in Mounjaro's warnings [1]. The Zepbound and Wegovy labels dropped their suicidal behavior warning in February 2026 [3]. Any change in mood is still worth reporting to your clinician, and thoughts of self-harm call for 911.
Serious risks on the Mounjaro label
- Pancreatitis. 14 confirmed events in 13 people on Mounjaro (0.23 per 100 patient-years) vs 3 in 3 comparator patients (0.11). Stop if pancreatitis is suspected [1].
- Gallbladder disease. 0.6% on Mounjaro vs 0% on placebo [1].
- Severe digestive reactions. 1.3% (5 mg), 0.4% (10 mg) and 1.2% (15 mg) vs 0.9% on placebo. Not recommended in severe gastroparesis [1].
- Kidney injury. Reported after approval, sometimes needing dialysis, mostly with dehydration from digestive side effects [1].
- Eyes. Temporary worsening of diabetic retinopathy has been reported with rapid improvement in blood sugar [1].
- Low blood sugar. More likely with insulin or a sulfonylurea [1].
- Allergic reactions. Anaphylaxis and angioedema have been reported [1].
- Anesthesia. Rare reports of pulmonary aspiration during anesthesia or deep sedation [1].
Thirst, peeing more or feeling dizzy can be signs of dehydration, which is the main path to kidney injury on the label [1]. Eye problems tie to the retinopathy warning; report any vision change.
Does Mounjaro cause cancer?
In rats, tirzepatide caused thyroid C-cell tumors, more often at higher doses and with longer use. It is not known whether it causes these tumors, including medullary thyroid carcinoma, in people [1]. Anyone with a personal or family history of medullary thyroid carcinoma or MEN 2 should not use Mounjaro [1]. Breast cancer and other cancers are not listed as known risks on the label.
Get help right away
Stop Mounjaro and call your prescriber for severe stomach pain that will not go away, with or without vomiting [1]. Call 911 for swelling of the face, lips or throat or trouble breathing [1]. With insulin or a sulfonylurea, treat shakiness, sweating or confusion as possible low blood sugar [1]. Tell your prescriber about a neck lump, trouble swallowing or a lasting hoarse voice [1].
Is Mounjaro approved for sleep apnea?
No. Mounjaro's label does not include sleep apnea [1]. FDA approved Zepbound, which contains the same medicine, for moderate to severe obstructive sleep apnea in adults with obesity on December 20, 2024 [6]. See Mounjaro vs Zepbound for how the two labels differ, Mounjaro cost for pricing, and GLP-1 side effects for the whole class.
Questions people ask
Does Mounjaro cause hair loss?
What is the most common side effect of Mounjaro?
Nausea. It affected 12% (5 mg), 15% (10 mg) and 18% (15 mg) of people in diabetes trials vs 4% on placebo [1].
How long do Mounjaro side effects last?
The label gives no duration. In SURMOUNT-1, digestive side effects were mostly mild to moderate and occurred mainly while the dose was being raised [4].
Does Mounjaro make you tired?
Fatigue was reported in 5% to 7% of people on tirzepatide in Zepbound weight trials vs 3% on placebo [2].
Does Mounjaro cause diarrhea or constipation?
Both. Diarrhea affected 12% to 17% and constipation 6% to 7% in diabetes trials, vs 9% and 1% on placebo [1].
Does Mounjaro cause cancer?
Tirzepatide caused thyroid C-cell tumors in rats; human risk is unknown. Do not use it with a personal or family history of medullary thyroid carcinoma or MEN 2 [1].
Can Mounjaro cause pancreatitis?
Yes. Confirmed pancreatitis occurred at 0.23 per 100 patient-years on Mounjaro vs 0.11 on comparators. Stop it and call your prescriber if suspected [1].
Is Mounjaro approved for sleep apnea?
No. Zepbound, which contains the same medicine, was approved for moderate to severe obstructive sleep apnea in adults with obesity on December 20, 2024 [6].
Do Mounjaro injections hurt?
Injection site reactions occurred in 3.2% of people on Mounjaro vs 0.4% on placebo [1].
Sources
6 cited
- Mounjaro (tirzepatide) injection prescribing information. DailyMed, U.S. National Library of Medicine, Aug 2026.
- Zepbound prescribing information, NDA 217806 (PDF). U.S. Food and Drug Administration, Apr 2026.
- Zepbound (tirzepatide) injection prescribing information. DailyMed, U.S. National Library of Medicine, Aug 2026.
- SURMOUNT-1 trial of tirzepatide in adults with obesity (Jastreboff et al., NEJM 2022), PubMed record. PubMed, National Library of Medicine, Jun 4, 2022.
- SURMOUNT-1 body composition substudy (Look et al., Diabetes Obes Metab 2025), PubMed record. PubMed, National Library of Medicine, Feb 25, 2025.
- FDA approves first medication for obstructive sleep apnea. U.S. Food and Drug Administration, Dec 20, 2024.
This page is general information, not medical advice. Talk with a licensed clinician about your own care.