Tirzepatide: Overview, how it works, and more

It doesn’t exactly roll off the tongue, but tirzepatide is getting talked about a lot at the moment. It’s the latest GLP-1 drug to get approval for type 2 diabetes (under the name Mounjaro) and weight loss (under the name Zepbound). Unlike other GLP-1s, tirzepatide is actually a combination of two hormones (GLP-1 and GIP), which may lead to even greater results. Here’s what that could mean for your health.

What is tirzepatide?

Tirzepatide is a GLP-1 that mimics the hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). These hormones play a major role in stimulating the pancreas to release insulin, which helps keep blood sugar regulated, as well as suppressing the appetite and prompting feelings of fullness, leading to weight loss.

Tirzepatide brand names

Tirzepatide can be prescribed under two brand names, Mounjaro and Zepbound. Mounjaro was approved by the FDA in May 2022 for type 2 diabetes management in adults as a way to improve blood sugar when combined with diet and exercise. Zepbound was approved a year and a half later, in November 2023, for chronic weight management in adults with obesity as well as those who are overweight and have at least one weight-related condition (like high blood pressure or high cholesterol). Similar to Mounjaro, the FDA notes that Zepbound should be used alongside a reduced-calorie diet and increased physical activity.

Tirzepatide uses

As the active ingredient in both Mounjaro and Zepbound, tirzepatide is used to help with both weight loss and blood sugar management. The Zepbound brand has an additional FDA approval to treat obstructive sleep apnea (OSA).

What is tirzepatide used for?

First approved for blood sugar management, tirzepatide can help improve A1C levels, which are a way to measure blood sugar over time. According to clinical trials, those taking the highest dose of tirzepatide (15 mg) achieved an A1C reduction of 2.46 percent. Even at the lowest dose of 5 mg, participants saw A1C reduction of 2.09 percent. In addition to improving blood sugar, the clinical trials showed that people with type 2 diabetes lost about 13 percent of their weight at the highest dose.

Research on people without diabetes showed those taking tirzepatide for 72 weeks lost around 20 percent of their body weight. This led to the medication getting approved for weight loss and weight management. To put this weight loss into perspective, the GLP-1 semaglutide (known by the brand names Ozempic and Wegovy) leads to an average weight loss of around 15%.

How does tirzepatide work?

Tirzepatide works by mimicking two different hormones in the body. The first hormone is GLP-1, short for glucagon-like peptide 1, which your body produces naturally whenever you eat. When you take tirzepatide, the hormone stays in your body for an extended period of time, signaling to the pancreas to release insulin and decrease glucagon to control blood sugar, as well as slowing the rate of stomach emptying, so you feel full for longer and have less of an appetite.

The second hormone in tirzepatide, glucose-dependent insulinotropic polypeptide (GIP), also impacts insulin production and slows digestion, thereby reducing hunger and improving blood sugar. The two hormones combined perform better than either one alone. This synergy is why tirzepatide may have a bigger impact than a medication that only contains GLP-1. One more health benefit of GIP: Some research suggests it may play a role in causing fat to break down faster in the body, further helping with weight loss.

"This dual mechanism of action with tirzepatide makes it a strong choice for weight loss and diabetes management," says Dr. Sue Decotiis, M.D., a triple board-certified physician in internal medicine, antiaging medicine, and obesity medicine, who leads a weight-loss practice in Scarsdale, NY. "Results will vary based on the individual, but in general, tirzepatide tends to be beneficial for long-term weight management."

Tirzepatide dosage

As with other GLP-1 medications, such as Ozempic or Wegovy, people taking tirzepatide usually start at the lowest dose and increase it slowly. This gives the body time to get used to the medication and reduces the risk for side effects.

Mounjaro dosing

Mounjaro, the version approved for type 2 diabetes, comes in six different dosages: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. Your provider will tell you which dose to take, but most people begin with the lowest dose and then gradually increase over time until they find a "maintenance dose" — the one they stay on — that works well for them, according to Dr. Alexandra Sowa, M.D., a New York City-based physician double-board certified in internal medicine and obesity medicine, and the author of The Ozempic Revolution. That could look like:

• Week 1-4: 2.5mg
• Week 5-8: 5mg
• Week 9-12: 7.5mg
• Week 13-16: 10mg
• Week 17-20: 12.5mg
• Week 21-onward: 15mg

"Keep in mind that you may be on a certain dosage for a longer period of time than four weeks if it seems that you're responding well to that amount," says Sowa. "For example, you may be doing well at 5mg, so that could be your long-term dose rather than continuing to increase the dosage."

Zepbound dosing

Zepbound, the version approved for weight loss, comes in the same six dosages as Mounjaro: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg and is usually increased at a similar pace:

• Week 1-4: 2.5mg
• Week 5-8: 5mg
• Week 9-12: 7.5mg
• Week 13-16: 10mg
• Week 17-20: 12.5mg
• Week 21-onward: 15mg

"Similar to Mounjaro or other GLP-1 medications, you'll be closely monitored to see how well you do on a specific dosage, and that will tend to determine if you increase," says Sowa.

Forms and strengths

Both Mounjaro and Zepbound come in prefilled injection pens that you use once per week. No matter which medication or dose you’re taking, your pen will contain 0.5 mL of solution. In addition to the drug tirzepatide, the solution contains stabilizers, water, and other inactive ingredients.

Tirzepatide side effects

With both Mounjaro and Zepbound, the frequency and intensity of side effects can vary from person to person, and you may feel more side effects when you increase your dosage, says Decotiis. "In some cases, you may not feel any side effects on lower dosages but could feel some as you go up," she says. "Many times, the effects are mild, but definitely talk with your doctor if they begin to affect your everyday activity and quality of life."

Common side effects

Because tirzepatide is given as an injection, you may notice redness, itchiness, or a painful sensation immediately around the site, which can last for a few hours but may linger for a couple days in some instances, according to Sowa. If you have a more serious allergic reaction — such as hives, swollen or blistering skin, or itching that keeps getting worse — reach out to your health provider immediately.

In addition to injection site reactions, other common side effects can include:

• Nausea
• Acid reflux
• Diarrhea
• Upset stomach
• Vomiting
• Dizziness
• Mood changes

For a full list of side effects, visit the Mounjaro and Zepbound websites.

Serious side effects

There is a small risk for more serious side effects when taking tirzepatide, including pancreatitis, gallbladder disease, and worsening of diabetic eye disease. That said, it’s important to note that research indicates these side effects are rare, happening in less than one percent of those taking the medication.

The FDA has also placed a warning on tirzepatide that anyone with a personal or family history of medullary thyroid cancer or multiple endocrine neoplasias should not take it. That's based on research showing rats developed thyroid tumors on tirzepatide, but there have not been any human studies showing the same connection.

Alternatives to tirzepatide

Since Mounjaro is used for managing type 2 diabetes, any medication that helps reduce blood sugar could be a possible alternative, including:

• Other GLP-1 receptor agonists like semaglutide (Ozempic), liraglutide (Victoza), and dulaglutide (Trulicity)
• Metformin
• DPP-4 inhibitors like linagliptin (Tradjenta) and sitagliptin (Januvia)
• SGLT2 inhibitors like empagliflozin (Jardiance) and dapagliflozin (Farxiga)
• Sulfonylureas like glimepiride (Amaryl) and glyburide (Diabeta)
• TZDs like rosiglitazone (Avandia) and pioglitazone (Actos)

If you are looking for an alternative weight-loss medication to Zepbound, your options include:

• GLP-1 receptor agonists like liraglutide (Saxenda) and semaglutide (Wegovy)
• Orlistat (Xenical, Alli)
• Naltrexone-bupropion (Contrave)
• Phentermine (Adipex, Suprenza)
• Phentermine-topiramate (Qsymia)

When considering alternatives, talk with your healthcare provider, so you can go over the pros and cons of each medication to find the one that’s right for you.

Tirzepatide warnings and precautions

According to the FDA, there were some serious health issues that occurred in clinical trials of people taking tirzepatide, including:

• Pancreatitis
• Hypoglycemia
• Hypersensitivity reactions
• Acute kidney injury
• Severe gastrointestinal disease
• Diabetic retinopathy complications
• Acute gallbladder disease

These are listed as precautionary because they were reported in a clinical trial, but there is not yet evidence that use of tirzepatide caused these issues.

The FDA also notes that there’s insufficient data about use of tirzepatide in pregnant women when it comes to drug-related risk of birth defects and miscarriage, but there is some evidence in animal studies that a fetus could be affected during pregnancy. Because of that, both Mounjaro and Zepbound are not recommended for use in women who are pregnant.

Tirzepatide interactions

The FDA notes that tirzepatide can interact with other drugs, so it's important to discuss all other medications you're taking with your provider. The ones most likely to increase health risks or cause other issues when taking tirzepatide include:

• Insulin or sulfonylureas, since taking these with tirzepatide can increase risk of hypoglycemia (low blood sugar)
• Blood thinners like warfarin, which may not get absorbed as well on tirzepatide
• Oral contraceptives, since tirzepatide can make those less effective (because of that, experts recommend using other birth control methods when taking either Mounjaro or Zepbound)

Tirzepatide cost and coupons

Mounjaro's retail price is $1,069.08 for a one-month supply, and Zepbound costs $1,086,37 per month, according to the manufacturer. How much of that (if any) is covered by insurance will depend on your plan. You may have more of a chance that Mounjaro is covered since type 2 diabetes medications tend to be covered more often than weight-loss drugs.

If your plan doesn’t include Mounjaro or Zepbound, you may be able to use a savings card from their manufacturer, Eli Lilly. Those who are eligible might pay as little as $25 for a one-month or three-month prescription. To be eligible for the savings programs, you must be prescribed the drug for the FDA-approved purpose, be enrolled in a commercial drug insurance plan, and not be part of any state, federal, or government funded healthcare program such as Medicare or Medicaid.

Tirzepatide storage

With both Mounjaro and Zepbound, the manufacturer recommends that you store all unopened pens in the refrigerator, but you may keep an unopened one outside of the refrigerator for up to 21 days. Just make sure the temperature doesn't get higher than 86 degrees Fahrenheit or cold enough to freeze the pen. You should also keep your Mounjaro or Zepbound pen in its original carton to protect it from direct sunlight, which can degrade the medication and make it less effective.

The bottom line

By bringing together two different hormones, tirzepatide has been shown to be effective in managing type 2 diabetes as well as helping with weight loss. The medication works by improving insulin response when you eat and reducing appetite by slowing gastric emptying. As with any medication, it's essential to talk with your health provider about your goals and to see if Mounjaro or Zepbound might be a fit for the next steps in your health journey.