How does tirzepatide work for weight loss?

Tirzepatide is the active ingredient in the prescription diabetes and weight loss medications Mounjaro and Zepbound. It primarily works by slowing down gastric emptying, reducing “food noise,” and balancing blood sugar. In clinical trials of people with obesity, tirzepatide led to an average weight loss of up to 20.9% in about a year and a half. Read on to learn more.

“For weight loss, tirzepatide slows gastric emptying, which slows down the passage of food in your stomach,” says Peminda K. Cabandugama, MD, a board-certified physician in obesity and endocrinology and Clinical Associate Professor of Medicine at the Cleveland Clinic.  

“If food is in your stomach longer, you'll be full longer and less hungry. Patients tell me that it also calms down food noise. Researchers think it affects the hypothalamus where our cravings come from,” Dr. Cabandugama says.

Here’s how tirzepatide works in your body:

• Appetite control: It targets two hormone receptors in areas of your brain that control hunger: glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). Together, this turns down your appetite and reduces intrusive thoughts about food, often called "food noise".

• Slower digestion: It delays gastric emptying, aka how fast food leaves your stomach. This physical fullness keeps you feeling satisfied much longer after a small meal.

• Blood sugar balance: It helps your pancreas release insulin properly after you eat and stops your liver from making extra, unneeded sugar. This steady blood sugar prevents the sharp crashes that normally trigger sudden hunger.

Tirzepatide can cause significant weight loss, according to clinical studies. Trial participants with obesity or overweight lost an average of about 15% of their body weight with the 5 mg dose, 19.5% with 10 mg, and 21% with 15 mg in 72 weeks (about a year and a half).

An analysis of ten studies found that people taking tirzepatide lost more weight, on average, than those taking other weight loss or diabetes medications. They lost 21.6 more pounds on average than those taking a placebo, 4.3 more pounds than those taking insulin, and 2.3 more pounds than those taking other GLP-1 medications. 

The studies ranged in duration from 12 to 72 weeks, and the participants in all but one of the studies had type 2 diabetes. 

In a separate trial of people with type 2 diabetes, tirzepatide led to an average weight loss of 12.8%–14.7% on the two highest doses of Mounjaro. In another study comparing Mounjaro vs. Ozempic, those taking tirzepatide 15 mg weekly lost 9.7% more body fat in seven months. Those taking Ozempic 1 mg weekly, on the other hand, lost just under 6%. 

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Tirzepatide starts working as soon as you take it, but it takes about four weeks before it reaches a steady concentration in your bloodstream. It’s around this point that people usually start to notice weight loss. 

From a diabetes management perspective, clinical trials of Mounjaro showed meaningful improvements in hemoglobin A1c (HbA1c) within about three months. The effect on blood sugar readings may appear sooner, but A1c takes longer to reflect the change because it measures average blood sugar levels over the past two to three months.

By three months, average HbA1c levels dropped to prediabetes levels (6.4%) or lower. And at the end of this 40-week study, HbA1c levels had dropped by 2%–2.3%, and the average body weight reduction was 7.6%–11.2%. 

Belly fat, or the fat stored in the abdomen, is often where many people on a weight loss journey want to see the most improvement. But can tirzepatide actually help you get rid of belly fat? 

“I get asked this by patients all the time,” says Dr. Cabandugama. “They’ll ask me, ‘Can you reduce the size of my belly (or breasts or thighs)?’ I tell them that is [only possible with] plastic surgery. Tirzepatide will help you lose weight, but weight can come from all different places.”

While it’s not possible to target your fat loss to a specific area (without plastic surgery), it’s likely that someone on tirzepatide will lose belly fat while reducing their overall body fat (participants in one clinical trial lost on average 7 inches from their waist).  

When it comes to maximizing weight loss on tirzepatide, the most important things are implementing healthy diet and exercise changes, and finding the right healthcare team. They can help you determine the right dosage for you and guide you toward the best results.

1. Find the right dosage of tirzepatide for you

It’s important to make sure you find the right dose for your body, Dr. Cabandugama says. While there is a standard dosage schedule, not everyone will benefit from the same titration. 

A modified dose-escalation schedule, while considered off-label since it is not the same as the manufacturer’s instructions, may be recommended by your medical team depending on your goals and side effects.

“The FDA did approve these medications’ doses to be increased every four weeks but you’ll see most of the folks who experience weight loss will not increase every four weeks unless they have to,” he says. 

“It’s not a race to get to the top dose; it’s about maximizing each dose of the medication,” he adds. “See a healthcare provider who will follow you closely to make sure you're doing well.”

2. Improve your diet and exercise routine

Tirzepatide works best when combined with lifestyle changes like a healthy diet and regular exercise. Certain foods can worsen tirzepatide’s side effects and hinder weight loss results, including heavy meals and fatty, fried, or ultra-processed foods. 

“See a dietitian or nutritionist to make sure you're maximizing your diet and getting enough protein intake, which is a building block for hair and nails,” says Dr. Cabandugama. “We’re not trying to stop you from eating; it’s about helping you go back to healthier choices when eating, and experience [fewer] cravings.”

To lose weight, it is important to eat less, but maintaining that weight loss requires regular exercise. According to Dr. Cabandugama, research consistently supports the importance of physical activity in sustaining long-term results, with guidelines recommending at least 150 minutes of exercise per week. 

Try to find a routine that works for you, whether it’s 1.5 hours a day on the weekend or 30 minutes a day throughout the week

3. Expand your healthcare team

Having a comprehensive approach to weight loss can maximize your results on tirzepatide. In addition to your prescribing practitioner, you may want to meet with other healthcare providers as well, such as a dietitian and, if needed, a plastic surgeon. 

“When patients lose a bunch of weight, they start to get loose or excess skin, which has its own weight, so having a multidisciplinary approach where you can get rid of that excess skin is also helpful,” says Dr. Cabandugama. 

Here are some questions you may want to ask your healthcare provider when you meet with them to discuss taking tirzepatide for weight loss.

• Is tirzepatide a good option for me based on my medical history, current health conditions, and weight loss goals?

• What kind of results should I realistically expect when taking tirzepatide for weight loss?

• How does tirzepatide compare to other weight loss medications?

• What is the appropriate starting dose for me, and how will my dose be adjusted over time?

• How long should I expect to take tirzepatide?

• What are the potential side effects of tirzepatide, and how common are they? How do I know when a side effect is normal vs. potentially serious?

• Are there any long-term risks associated with using tirzepatide for weight loss?

• Will tirzepatide interact with any other prescription or over-the-counter medicines I’m currently taking?

• Do I need to follow a specific diet or exercise plan while taking tirzepatide?

• How will my progress be monitored while I’m on tirzepatide?

• What signs or symptoms should I look for that might indicate a problem or the need to adjust my treatment?

• Is tirzepatide covered by my insurance plan, and what are the out-of-pocket costs?

• Are there patient assistance programs or discounts available for tirzepatide?

• If tirzepatide doesn’t work for me, what other options do you recommend?

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How you take tirzepatide depends on whether your medication comes in a prefilled pen or in a vial. 

How to inject a tirzepatide pen

Here’s how to inject a tirzepatide pen, using the US Food and Drug Administration (FDA)’s instructions for the Zepbound KwikPen and the Mounjaro KwikPen. Be sure to follow the instructions that come with your medication, as the steps differ for single-dose pens.

1. Wash your hands thoroughly with soap and water.

2. Inspect the pen. Confirm that you have the right dose and that the medication has not expired. The medicine should be clear and colorless (or slightly yellow). If it is frozen, cloudy, or contains particles, dispose of the pen and use a new one.

3. Pull off the cap and wipe the red inner seal with an alcohol swab. 

4. Select your pen needle and pull the paper tab off of the needle shield. Then, push the capped needle into the pen, twisting it until it’s on tight. Pull off the outer needle shield. (Hold on to this — you’ll need it again). Then, take off the inner needle shield and throw it out. 

5. Prime the KwikPen by turning the dose knob until you hear 2 clicks. Hold the pen with the needle pointing up, then gently tap the cartridge so any air bubbles go to the top. Next, push the dose knob in slowly until it stops, and then count to 5 while holding the dose knob. This should release a bit of the medicine into the air.

6. Choose your injection site. It can be the back of your upper arm if someone is helping you, or if you’re self-injecting, you can choose the front or outer side of your thigh, or anywhere on your abdomen at least two inches away from your belly button. Be sure to rotate injection sites, choosing a spot that’s at least one finger’s width away from where you last injected tirzepatide. Avoid areas with scars, rashes, or bruises.

7. Turn the knob on the pen until it stops and the “1” icon is in the dose window.

8. Insert the needle straight into your skin. Push the dose knob in until it stops. Count to 5 slowly while holding the dose knob. Make sure the “0” icon is showing before you pull the needle out of your skin.

9. If there’s any blood at the injection site, apply gentle pressure with gauze or a cotton ball.

10. Replace the outer needle shield and then unscrew the capped needle. Put the needle into a sharps container.

11. Replace the pen cap and store it safely for next week. 

How to inject tirzepatide from a vial

If your tirzepatide comes in a vial, follow these steps to inject it: 

1. Wash your hands thoroughly with soap and water.

2. Remove the vial from the refrigerator and gather your sterile syringe with a needle and two alcohol wipes.

3. Inspect the vial. Confirm that you have the right dose and that the medication has not expired. The medicine should be clear and colorless (or slightly yellow). If it is frozen, cloudy, or contains particles, do not use it.

4. Shake and clean the vial. Pull off the plastic cap, but keep the rubber stopper in place. Clean the top of the rubber stopper with one of your alcohol wipes.

5. Remove the caps from the plunger and the needle. Do not touch the needle while you do this, so things stay sterile.

6. Hold the syringe with the needle pointing up. Pull down the plunger to fill the needle with air up to the 0.5 mL line.

7. Place the vial on a flat surface and insert the needle into the vial. Push down to inject all of the air into the vial.

8. With the needle still inside the vial, turn the vial upside down. The needle tip should be surrounded by liquid.

9. Pull the plunger just past the 0.5 mL line.

10. Flick the syringe with your finger to remove any air bubbles.

11. Push the plunger back up to the 0.5 mL line.

12. Remove the syringe from the vial and apply a new seal sticker to the cap of the vial.

13. Choose your injection site. It can be the back of your upper arm (if someone’s helping you), the front or outer side of your thigh, or anywhere on your abdomen at least two inches away from your belly button. Choose a spot that’s at least one finger’s width away from where you last injected tirzepatide. Avoid areas with scars, rashes, or bruises.

14. Wipe your skin with your second alcohol wipe. Let it dry.

15. Hold the syringe with the needle facing up, and push down on the plunger just enough for a drop of liquid to form at the end of the needle.

16. Pinch the skin at your injection site (if advised to do so by your prescriber) and quickly push the needle into it, making sure to insert the full length of the needle. Slowly push down on the plunger to inject your full dose, keeping the needle in your skin for at least five seconds.

17. Pull out the needle and discard the syringe in a FDA-cleared sharps disposal container. If you bleed, gently press on the area with a cotton ball or an alcohol swab — don’t rub it.

Tirzepatide is a prescription medication, so you’ll need to see a healthcare provider in order to get it. Here are the steps you can take to get tirzepatide for weight loss or type 2 diabetes, either online or in-person.

Step 1: Consult a healthcare provider

The first step in getting tirzepatide is making an appointment with a licensed healthcare provider who can write prescriptions. You can meet with your primary care physician (PCP),  endocrinologist, or weight loss specialist. 

If you prefer, you can also connect with a healthcare provider online through a direct-to-patient healthcare company such as Ro. Direct-to-patient companies offer a convenient way to access medications like tirzepatide, particularly for those who prefer virtual consultations or want to get their medication faster.

During your appointment, your healthcare provider will determine if tirzepatide is the right treatment option for you. Come prepared to share your medical history, current medications and health conditions, and goals for weight loss or type 2 diabetes. (With a company such as Ro, you may answer these questions before your visit via an online questionnaire). 

This information helps your provider assess whether tirzepatide is a safe and effective option for you. They may also order lab tests before recommending tirzepatide or another treatment.

If you and your healthcare provider decide tirzepatide is a good option for you to try, they’ll write you a prescription.

Step 2: Verify your insurance coverage

It can be helpful to confirm whether your insurance plan covers tirzepatide before you head to the pharmacy. Some direct-to-patient healthcare companies, including Ro, will connect with your insurance plan on your behalf to determine coverage. Not all insurance plans cover tirzepatide. When they do, prior authorization is typically required. 

This means your healthcare provider will need to submit paperwork to your insurance plan showing that you: a) are taking tirzepatide for an FDA-approved condition (e.g., type 2 diabetes in the case of Mounjaro and weight management, or sleep apnea in the case of Zepbound) and b) meet certain criteria. 

These criteria can depend on the insurer and which brand name version of tirzepatide you are taking:

• For Mounjaro, you will need a diagnosis of type 2 diabetes, with or without a high risk of major cardiovascular problems. 

• For Zepbound, you will need to have obesity or overweight with a weight-related health condition such as high blood pressure, high cholesterol, or type 2 diabetes. Or you will need to have obesity and moderate to severe obstructive sleep apnea. 

If your insurance doesn’t cover tirzepatide, there are still ways you can save on the cost of tirzepatide. Eli Lilly offers Savings Cards for both Mounjaro and Zepbound that can bring the cost down significantly for eligible individuals. There are also several websites, such as GoodRx, Optum Perks, or SingleCare, that share pharmacy-specific coupons for Zepbound and Mounjaro.

Step 3: Fill your prescription

When you’re ready to fill your prescription, you can either bring it to your preferred pharmacy or have your provider send it electronically. 

If you received your prescription through a company like Ro, they’ll handle the process of filling it for you. Many direct-to-patient healthcare companies (including Ro) will ship tirzepatide directly to your home, and some local pharmacies offer home shipping as well. 

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Tirzepatide (the active ingredient in Mounjaro and Zepbound) is a dual GLP-1 and GIP receptor agonist. This combination enhances insulin release, reduces glucose production, slows gastric emptying, and reduces appetite, making it more effective for weight loss and type 2 diabetes than single GLP-1 receptor agonists like Ozempic and Wegovy.

• Tirzepatide works for weight loss by keeping food in the stomach for longer (helping you feel fuller longer), and decreasing appetite, cravings, and food noise in the brain. 

• Clinical trials showed tirzepatide can produce an average weight loss of 15%–20.9% over 72 weeks.

• Tirzepatide is available in prefilled pens or vials. To take tirzepatide, you give yourself a subcutaneous injection once a week. It starts working immediately, but significant weight loss and improved blood sugar control typically become noticeable within the first few months of use.

• Tirzepatide has some downsides, including a long list of potential side effects and a high out-of-pocket cost. Many of tirzepatide’s most common side effects, like nausea, diarrhea, and abdominal pain, typically subside over time. 

• Rare but serious side effects include pancreatitis, gallbladder issues, and kidney problems. It is also expensive, and insurance coverage may vary depending on whether it’s prescribed for type 2 diabetes or weight loss.