Mounjaro side effects and how to avoid them

Mounjaro side effects include GI side effects, rapid heart rate, injection site reactions, and increased pancreatic enzymes

Common Mounjaro side effects | Serious side effects | GI problems | Thyroid cancer risk | Pancreatitis | Weight loss |  Hypoglycemia | Side effects timeline | Contraindications and warnings | Interactions | How to avoid side effects | How to treat side effects

Diabetes mellitus, more commonly known simply as diabetes, is a condition in which the body’s ability to produce or respond to the hormone insulin is impaired, resulting in high blood sugar (hyperglycemia). In people with Type 1 diabetes, the pancreas no longer makes insulin and insulin shots are required to utilize the sugars from food. Those with Type 2 diabetes, on the other hand, have many more treatment options. The drugs commonly used to treat Type 2 diabetes, such as metformin,  either have a direct effect on improving insulin secretion or a direct effect on improving the use of the available insulin by the body’s cells.

Mounjaro (tirzepatide), made by Eli Lilly and Company, is approved by the U.S. Food and Drug Administration (FDA) for adults 18 years and older to treat Type 2 diabetes mellitus as an adjunct to diet and exercise. Mounjaro is used to improve blood sugar, or glucose, levels, by limiting how much glucose gets into the bloodstream, slowing down food digestion in the stomach, and helping the pancreas release insulin following a meal. Mounjaro is an injectable drug in a class of medicines known as glucagon-like peptide-1 (GLP-1) receptor agonists. Other FDA-approved GLP-1 receptor agonist drugs include Ozempic (semaglutide), Trulicity (dulaglutide), and Victoza (liraglutide). Mounjaro is available as a single-dose pen and is given once a week by subcutaneous injection.

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As with any medication, it is important to be aware of possible side effects and other drug interactions. The following drug information highlights potential Mounjaro side effects and how to avoid them.

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Common side effects of Mounjaro

The most common side effects of Mounjaro are gastrointestinal (GI) related and include:

  • Nausea
  • Diarrhea
  • Decreased appetite
  • Vomiting
  • Constipation
  • Indigestion
  • Stomach pain
  • Burping
  • Gastroesophageal reflux disease (GERD)

In clinical trials, most nausea, vomiting, and diarrhea events occurred while the dose of Mounjaro was being increased. These events decreased over time.

Additional common side effects may include:

  • Heart rate increase (tachycardia)
  • Injection site reactions
  • Increased blood levels of pancreatic enzymes amylase and lipase

Serious side effects of Mounjaro

Although not common, Mounjaro may cause serious side effects, including:

  • Severe stomach problems 
  • Risk of thyroid cancer 
  • Pancreatitis (inflamed pancreas)
  • Hypoglycemia (low blood sugar) 
  • Serious allergic reactions 
  • Acute kidney injury 
  • Changes in vision
  • Acute gallbladder problems

Severe stomach problems

GI side effects are the most common adverse events associated with the use of GLP-1 receptor agonists, including Mounjaro. Most GI side effects occur when therapy begins, are mild or moderate in severity, and decrease with continued treatment. GI side effects tend to be dose-dependent, i.e., the higher the strength of the starting dose the greater the incidence of GI side effects. In clinical trials, 3.0% of patients receiving the 5 mg dose, 5.4%  of patients receiving the 5 mg dose, and 6.6% of patients receiving the 15 mg dose discontinued treatment due to severe GI adverse reactions.

Risk of thyroid cancer

In animal studies, GLP-1 receptor agonists, such as Mounjaro, led to the formation of thyroid tumors in mice and rats. Based on these findings in rodents, it was hypothesized that these medications had the potential to cause thyroid cancer in humans as well. This finding led to all GLP-1 receptor agonists having a mandated “boxed warning,” also called a black box warning, from the FDA. 

It is unknown whether Mounjaro causes thyroid C-cell tumors, including medullary

thyroid carcinoma (MTC). Mounjaro is contraindicated in patients with a personal or family history of MTC or in patients with multiple endocrine neoplasia syndrome type 2 (MEN 2). 

Inflammation of the pancreas (pancreatitis)

The pancreas is a large gland located behind the stomach that produces digestive enzymes and hormones that help regulate glucose levels in the body. Pancreatitis occurs when the digestive enzymes it produces do not leave the pancreas and start to damage its own tissue causing inflammation.

Acute pancreatitis has been reported in patients treated with GLP-1 receptor agonists including Mounjaro. It is unknown if patients with a history of pancreatitis are at higher risk for the development of pancreatitis on Mounjaro. If signs and symptoms of pancreatitis should occur, which include severe pain in the stomach or abdomen, with or without vomiting,  Mounjaro should be discontinued and the healthcare professional should be contacted.

Weight loss

Although not FDA-approved as a weight loss medicine, in clinical studies Mounjaro demonstrated significant weight reduction from baseline for trial participants on any of the three starting doses.

 At the highest dose of the medication (15 milligrams) Mounjaro reduced body weight, on average, by about 28 pounds. This secondary effect is important for those with Type 2 diabetes whose excess weight often contributes to worse health outcomes. This makes Mounjaro a good choice for those with Type 2 diabetes who would benefit from losing weight.

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Low blood sugar (hypoglycemia)

Hypoglycemia is when blood sugar, or glucose, levels have fallen low enough that action is necessary to bring blood sugar levels back to a normal range. Hypoglycemia may last for several hours and severe hypoglycemia may even require medical treatment.

The risk of getting hypoglycemia may be higher if Mounjaro is combined with another diabetic medicine that may also cause low blood sugar, such as a sulfonylurea or insulin. Signs and symptoms of low blood sugar may include dizziness or light-headedness, sweating, confusion or drowsiness, headache, blurred vision, slurred speech, shakiness, fast heartbeat, anxiety, irritability or mood changes, hunger, weakness, and feeling jittery.

Serious allergic reactions

There have been reports of serious hypersensitivity reactions, including anaphylactic reactions, in people using GLP-1 receptor antagonists, including Mounjaro. Symptoms of a serious allergic reaction include:

  • Swelling of the face, lips, tongue, or throat
  • Problems breathing or swallowing
  • Severe rash or itching
  • Fainting or feeling dizzy
  • Very rapid heartbeat

Should any of these symptoms occur while taking Mounjaro a healthcare professional should be notified immediately.

Acute kidney injury

In those people who have existing kidney problems, Moujanro’s side effects of diarrhea, nausea, and vomiting may cause a loss of fluids (dehydration), which may cause kidney problems to worsen. Healthcare professionals may need to closely monitor kidney function in these patients if they experience severe GI side effects leading to dehydration.

Changes in vision

People with diabetes may develop an eye condition called diabetic retinopathy, a condition that can cause damage to the tiny blood vessels of the retina (the thin layer of tissue at the back of the eye near the optic nerve). In clinical studies, patients treated with GLP-1 agonists, including Mounjaro, with a history of diabetic retinopathy reported increased symptoms including:

  • Spots in vision
  • A dark area in central vision
  • Trouble seeing at night
  • Colors looking faded or washed out
  • Vision changes from blurry to clear 

Should any of these symptoms occur while taking Mounjaro a healthcare professional should be contacted.

How soon do Mounjaro side effects start?

Many of the most commonly-experienced GI side effects of Mounjaro occur when initiating treatment: nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia, and abdominal pain. These symptoms may worsen during the first few weeks or months, as the dose is increased, but should begin to lessen once the optimal dose is established. Less common, but more serious side effects, such as severe stomach problems, development of thyroid tumors, or pancreatitis, are typically delayed and may take months or years of drug use to occur.

How long do Mounjaro side effects last?

Common side effects typically go away within a few days or weeks after initiating therapy or following dose adjustments, or once the body has adjusted to the medicine. Injection site reactions can be minimized by routinely changing the location of the injections. More serious side effects, such as kidney problems, thyroid tumors, or pancreatitis, will likely require the discontinuation of Mounjaro.   

Mounjaro contraindications and warnings


Mounjaro should not be used with any of the following conditions:

  • Type 1 diabetes
  • Younger than 18 years of age
  • Personal or family history of medullary thyroid carcinoma (MTC)
  • History of multiple endocrine neoplasia syndrome type 2 (MEN 2)
  • Allergic to any ingredients in Mounjaro


In the event of an overdose, notify the healthcare professional or Poison Control Center. A few days of observation and treatment for symptoms such as nausea and vomiting or mild hypoglycemia may be necessary due to the half-life of Mounjaro of approximately 5 days.

Pregnancy and breastfeeding

While there is limited data regarding the use of Mounjaro in pregnant women, there are health considerations regarding the risks of poorly controlled diabetes in pregnancy. Based on animal studies, there may be risks to the fetus from exposure to Mounjaro during pregnancy and it should only be used if the potential benefit justifies the potential risk. 

Similarly, there is little information on the presence of Mounjaro in human breast milk or on the effects on the breastfed infant. Mounjaro should only be used if the potential benefit justifies the potential risk.

A woman’s healthcare provider is the best source of information when managing Mounjaro and other diabetes treatments while pregnant or breastfeeding.

Abuse and dependence

Mounjaro is not habit-forming or addictive, however abrupt discontinuation may result in  increased blood glucose levels. Always consult with a healthcare professional before discontinuing Mounjaro or switching to another diabetes medicine.

Mounjaro interactions

Because Mounjaro slows down digestion and the rate that food empties from the stomach, it may affect the rate of absorption of other oral medications. This may be important for those drugs where small differences in absorption and blood levels can have an impact on their effectiveness. When taking other medicines to treat diabetes, such as insulin or sulfonylureas, there is an increased risk of hypoglycemia. For these reasons, it is important before starting Mounjaro to discuss other prescription medicines or over-the-counter drugs, vitamins, or herbal supplements a person takes with their healthcare professional.

Birth control pills taken by mouth may not work as well while using Mounjaro. The healthcare provider may recommend using another type of birth control for four weeks after initiating Mounjaro therapy and for four weeks after each increase in the dose. Hormonal

contraceptives that are not administered orally should not be affected.

How to avoid Mounjaro side effects

Talk to a doctor about your health history

Discuss the following with your healthcare provider before beginning Mounjaro therapy:

  • Do you have any other medical conditions, such as problems with your pancreas, kidneys, liver, or stomach, or have a history of diabetic retinopathy (vision problems related to diabetes)?
  • Do you have GI problems, such as slowed gastric emptying or problems with digesting food?
  • Do you take any other diabetes medications, e.g., insulin or sulfonylureas?
  •  Do you take any other prescription drugs or over-the-counter drugs, vitamins, or herbs?
  • Are you pregnant or do you plan to become pregnant?
  • Are you breastfeeding or do you plan to breastfeed?

Use Mounjaro at the same time and on the same day

Mounjaro comes in a disposable, prefilled pen and is injected once weekly under the skin (subcutaneously) in your thigh, upper arm, or stomach. You should administer Mounjaro at the same time and on the same day each week. Allow at least three days to pass between injections if you must change from your previously scheduled day. Other Mounjaro dosage tips include:

  • Mounjaro may be given without regard to meals or food.
  • When injecting Mounjaro, inject in a different place each time, i.e., don’t use the same injection site twice in a row. Your healthcare provider should provide medical advice on the best places to inject.
  • If you miss a scheduled dose and there are at least three days (72 hours) until the next dose, you should administer it as soon as possible and then resume your usual once-weekly dosing schedule. If you miss a dose and the next regularly scheduled dose is due in one or two days, do not inject the missed dose and instead resume Mounjaro with the next regularly scheduled dose.
  • Store Mounjaro in the refrigerator at (36 to 46 degrees Fahrenheit) and not the freezer; do not use Mounjaro if it has been frozen.
  • If needed, each single-dose pen can be kept at room temperature, not to exceed 86 degrees Fahrenheit for a total of 14 days. 
  • Read and carefully follow the instructions that come with the Mounjaro Pen. Ask your healthcare provider if you do not understand the instructions.

How to treat side effects of Mounjaro

GI side effects are the most common side effects of Mounjaro, particularly when initiating therapy or adjusting the dose. If you experience nausea:

  • Eat four or more smaller meals instead of three meals a day
  • Stop eating when you feel full
  • Eat bland foods and avoid fried or fatty foods

If you experience hypoglycemia (low blood sugar), eat or drink something with a high sugar content such as a non-diet soda, fruit juice, or hard candy. Your healthcare provider may prescribe a glucagon injection kit that may be used for severe hypoglycemia.



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