Tirzepatide Side Effects: Everything You Need to Know

Mounjaro® and Zepbound® are two popular medications that support diabetes care and weight loss. Both brand names contain the same active ingredient: tirzepatide. If you’re prescribed one of these meds, it’s worth reading up on tirzepatide side effects.

While tirzepatide is generally considered safe and effective when taken as prescribed, there are a few side effects to be aware of.

We’ll provide an overview of how tirzepatide works, then walk you through all the common side effects, along with the more severe but less common ones, and other risks to know about.

Tirzepatide is the active ingredient in the brand-name drugs Mounjaro and Zepbound. These medications are both manufactured by Eli Lilly and Company.

Tirzepatide is used to treat type 2 diabetes and support weight loss in individuals with overweight and obesity. Other well-known options include semaglutide and liraglutide.

Mounjaro is approved by the U.S. Food and Drug Administration (FDA) to treat type 2 diabetes by controlling blood sugar (glucose) levels. Mounjaro is also prescribed off-label for weight loss.

(Off-label use is when a medication is prescribed by a licensed medical provider to treat something it’s not FDA-approved for.)

Zepbound, on the other hand, is FDA-approved for weight loss in adults with obesity or overweight (based on body mass index, or BMI) with at least one weight-related condition, including:

• High blood pressure (hypertension)

• Type 2 diabetes

• High cholesterol

• Sleep apnea

Tirzepatide is prescribed alongside a healthy eating plan and regular exercise to support healthy blood sugar levels and weight management. Both drugs are administered as a once-weekly subcutaneous (under the skin) injection.

Before we lay out the side effects of tirzepatide, let’s briefly unpack its mechanism of action — i.e., how it actually works in the body.

Tirzepatide side effects have a lot to do with how the medication works.

Tirzepatide targets two receptors in the body. It’s both a GLP-1 receptor agonist and an insulinotropic polypeptide (GIP) receptor agonist. For short, it’s known as a GIP/GLP-1 receptor agonist.

GLP-1 Receptor Agonist

GLP-1 is a hormone naturally produced in the digestive tract after eating. GLP-1 medications imitate the hormone glucagon-like peptide-1, which affects the part of the brain responsible for regulating appetite.

To get into the weeds a bit more, the GLP-1 receptor agonist component of tirzepatide works by encouraging the pancreas to produce more insulin to keep blood sugar levels healthy. It also reduces hunger and promotes feelings of fullness.

GIP Receptor Agonist

What about the GIP component of this medication? It’s pretty similar.

The GIP receptor agonist element works by mimicking the GIP hormone. The GIP hormone is also released after eating to trigger insulin production and is also linked with feelings of fullness.

Together, these two receptor agonists work to reduce appetite and food intake, both of which can promote weight loss — according to an Eli Lilly-sponsored study on tirzepatide.

Other medications, like semaglutide (the active ingredient in Ozempic® and Wegovy®), only mimic GLP-1.

Tirzepatide comes in six different strengths. The lowest recommended dose is 2.5 milligrams (mg) or 0.5 milliliters (ml). Your healthcare provider may increase your dosage after four weeks.

Like all medications, tirzepatide comes with the potential for side effects. The milder ones are the most common and usually short-lived, but there are a few more serious risks to be aware of.

Let’s unpack them ahead.

What Are the Most Common Side Effects of Tirzepatide?

The most common tirzepatide side effects are gastrointestinal. They’re usually reported during the first couple weeks of treatment or during dosage increases while the body adjusts.

Common side effects of tirzepatide include:

• Nausea

• Diarrhea

• Decreased appetite

• Vomiting

• Dyspepsia (indigestion with pain in the upper abdomen)

• Constipation

• Abdominal pain

More gastrointestinal side effects include feeling gassy and having acid reflux (heartburn).

Tirzepatide Side Effects When Starting Treatment and Increasing Doses

It’s worth repeating that these Mounjaro and Zepbound side effects can be expected at the beginning of treatment or when the dosage is increased. There’s a decent chance they’ll subside once your body adjusts after a few weeks.

Some people taking tirzepatide manage nausea, diarrhea, and stomach pain with over-the-counter medications during the first couple of weeks while they adjust to the meds.

It’s always a good idea to stay in close contact with your healthcare provider about your side effects. If your side effects are severe, they might want to slow your dose titration schedule (meaning pumping the breaks on raising your dose) and can offer personalized medical advice.

Another thing to keep in mind is that, like other methods of weight loss, weight can be regained after using weight loss injections.

One study sponsored by Eli Lilly followed people without diabetes who had overweight or obesity. Participants who took 10 to 15 milligrams of weekly tirzepatide gained most of their lost weight back after stopping tirzepatide after 36 weeks of treatment.

They had an average of 14 percent weight regain after losing 20.9 percent of their initial body weight during the first 36 weeks. Those who stayed on tirzepatide through the 52-week study saw an additional 5.5 percent of weight loss. This highlights the importance of ongoing treatment.

What Are the Serious Side Effects of Tirzepatide?

Tirzepatide can also cause more serious health problems, although these issues are rare.

Other possible side effects of tirzepatide include:

• Tachycardia (increased heart rate)

• Hypoglycemia (low blood sugar)

• Dehydration

• Allergic reaction to the drug

• Kidney problems

• Injection site reactions

Stop using Mounjaro or Zepbound and see immediate medical attention if you exhibit signs of a severe allergic reaction, like:

• Trouble breathing or wheezing

• Difficulty swallowing or hoarseness

• Hives or skin rashes

• Swelling of the face

• Vision changes

• Really rapid heartbeat

Weight loss injections also have certain contraindications. This means healthcare providers may not recommend them to some patients.

Tirzepatide might not be a good fit if you have:

• Type 1 diabetes

• Diabetic retinopathy (an eye condition that can happen in people with diabetes)

• Gallstones or other gallbladder problems (cholelithiasis)

• A history of pancreatitis

• Family or personal history of thyroid tumors or thyroid cancer, specifically medullary thyroid carcinoma (MTC) and endocrine neoplasia syndrome type 2 (MEN2)

Clinical trials on rodents have shown that these medications can cause an increase in thyroid C-cell tumors, but this hasn’t been observed in human studies.

There isn’t much research on the safety of tirzepatide while pregnant or breastfeeding.

In some cases, a healthcare provider might decide a medication is worth prescribing when the benefits outweigh the potential risks (like treating diabetes, for instance).

According to research cited in the FDA’s prescribing information for Mounjaro, animal studies show that it could cause harm to the fetus.

The same is true for clinical trials reviewed by the FDA as part of Zepbound’s approval. But the label also states that the medication should be discontinued if pregnant.

As always, it’s best to consult your healthcare provider to discuss your specific health needs.

Compound Tirzepatide Side Effects

Compounded tirzepatide is a version of the medication made by a compounding pharmacy — a pharmacy that creates and sells custom medications. These pharmacies are overseen by state boards but aren’t regulated by federal standards.

Compounded tirzepatide from a state-licensed pharmacy that follows the FDA’s Current Good and Manufacturing Practice guidelines is generally considered safe. But it won’t be FDA-approved, so the FDA can’t confirm its safety or effectiveness.

Keep in mind that the FDA advises getting semaglutide with a prescription from a licensed healthcare provider. The same advice can be applied to tirzepatide.

Since tirzepatide delays gastric emptying, it might affect how your body processes other medications.

Make sure to discuss all your current medications with a healthcare professional to review any potential interactions, including those with birth control pills.

Your healthcare provider may suggest using a different type of contraceptive while on tirzepatide. For women using oral contraceptives, the FDA advises switching to a non-oral method or adding a barrier method (like condoms) for the first month of treatment and for four weeks after each dose increase.

Also, combining tirzepatide with secretagogues (another class of type 2 diabetes medications) may increase the risk of hypoglycemia.

You may be wondering how the side effects of tirzepatide weight loss medications stack up against those of semaglutide medications like Ozempic and Wegovy.

The side effects of semaglutide injections are similar to the tirzepatide side effects we just covered. Some common side effects are even more common when the medication dosage is higher or increased. This is true for both semaglutide and tirzepatide.

Over five percent of people report nausea and diarrhea while on 2 milligrams or less of semaglutide. These adverse reactions affect up to 10 percent of people who use tirzepatide.

What about the more serious but rarer side effects?

A 40-week trial supported by Eli Lilly looked at the effects of tirzepatide versus semaglutide in people with type 2 diabetes. The goal of the study wasn’t to measure weight loss rates, but the researchers noted that those who used tirzepatide lost more weight than those who received semaglutide.

That said, the Eli Lilly-sponsored study also found that five to seven percent of people who used tirzepatide experienced serious side effects — as opposed to only three percent who used semaglutide.

You can learn more in our guide comparing tirzepatide and Ozempic.

While weight loss injections and type 2 diabetes medications like Zepbound and Mounjaro can be great tools for a lot of people, it’s wise to be aware of their potential side effects.

Here’s what to keep in mind about tirzepatide and its possible side effects:

• Tirzepatide brand names are Mounjaro and Zepbound. Mounjaro is FDA-approved to treat type 2 diabetes but can be prescribed off-label for weight loss. Zepbound is FDA-approved for weight loss in adults with obesity or overweight with at least one weight-related health condition.

• Tirzepatide injections are dual GLP-1/GIP receptor agonists. They mimic the GLP-1 and GIP hormones, which can help control blood sugar levels, reduce cravings, and regulate appetite.

• Common side effects of tirzepatide include nausea, diarrhea, and abdominal pain. These are most common at the beginning of treatment or when the dosage is increased while your body adjusts to the medication. More serious adverse reactions include low blood sugar, gallstones, and rapid heart rate.

• Tirzepatide is generally safe when used as directed. Tirzepatide is considered safe and effective when used as prescribed alongside healthy habits, like mindful eating and regular physical activity.

If you’re curious about weight loss medications, check out the offerings on our telehealth platform.

And if you’re interested in getting a prescription from a licensed medical provider, you can start by doing our free online weight loss assessment.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.