What Is the Mounjaro Weight-Loss Pen?

What Is Mounjaro?

Mounjaro is a weight-loss pen, an injectable medication used under a pharmacist's or doctor's guidance. Its active ingredient is tirzepatide, which works by activating both GLP-1 and GIP hormone receptors to help control appetite, keep you feeling fuller for longer, reduce hunger, and make weight management easier and more natural.

The Mounjaro weight-loss pen is injected once a week under the skin of the thigh, abdomen, or upper arm. Treatment typically starts at a low Mounjaro dose (2.5 mg) and is increased every 4 weeks until reaching the maintenance dose that suits each individual, keeping the Mounjaro dose aligned with both goals and safety.

How Does Mounjaro Help With Weight Control?

The active ingredient tirzepatide in Mounjaro mimics two gut hormones (GLP-1 and GIP) that the body naturally releases after eating. It acts on the areas of the brain that regulate hunger, supporting weight management through several key mechanisms:

  • Reducing the amount of food eaten

  • Keeping you feeling fuller for longer

  • Slowing the movement of food through the stomach

Thanks to its ability to help control appetite and blood sugar levels, the Mounjaro weight-loss pen can help with

  • Making it easier to reduce calorie intake

  • Reducing appetite and cravings for sweets

  • Helping limit blood sugar fluctuations

When Does Mounjaro Start Working?

Mounjaro can begin working within just a few hours of the first injection. That said, noticeable results usually start to show over the first several weeks, since the Mounjaro dose is increased gradually to reduce the risk of side effects and allow the body to adjust properly.

If, after 6 months of continuous use, weight loss has not reached at least 5% of starting body weight, a pharmacist or doctor may consider stopping treatment, as it may not be the right option for that individual.

How Much Weight Can You Lose?

Clinical studies have shown that the Mounjaro weight-loss pen can support weight loss of up to approximately 22.5% of starting body weight* over 72 weeks, when used at the highest maintenance Mounjaro dose of 15 mg per week.

For the best results, Mounjaro should be combined with lifestyle changes such as a balanced diet and regular exercise, supporting long-term, sustainable body shape and quality of life.

Results may vary from person to person, depending on eating habits, exercise, and individual factors.

How Long Do You Need to Use the Mounjaro Weight-Loss Pen?

The Mounjaro weight-loss pen is generally designed for long-term body management. However, if weight loss still hasn't reached 5% of starting body weight within 6 months even at the maximum dose, it may be time to consult a pharmacist about adjusting your approach or considering another option better suited to your body.

What Happens If You Stop Using the Mounjaro Weight-Loss Pen?

It's not recommended to stop using this medication on your own without consulting a pharmacist first.

Once you stop using the Mounjaro weight-loss pen, its effects gradually wear off, which may cause appetite to return to previous levels and lead to weight regain. Gradually tapering the dose under guidance is a more suitable approach. Maintaining healthy eating habits and regular exercise will also help you keep your results for as long as possible.

Who Is a Good Fit for the Mounjaro Weight-Loss Pen?

To help ensure that using the Mounjaro weight-loss pen is safe and effective, here are some general guidelines for who might consider it:

  • Individuals with a BMI of 30 kg/m² or higher
  • Individuals with a BMI of 27 kg/m² or higher who also have a weight-related health condition (such as high blood pressure)

If you're not sure what your BMI is, you can use the free BMI calculator available on our website.

The Mounjaro weight-loss pen is also used to help manage type 2 diabetes in adults, supporting better blood sugar control, either on its own or alongside other medications as advised.

How to Use the Mounjaro Weight-Loss Pen

To make using the Mounjaro weight-loss pen smooth and safe, please carefully follow the steps in the product's instruction leaflet, as outlined below:

Getting Ready Before Using the Mounjaro Weight-Loss Pen

  1. Wash your hands thoroughly with soap and warm water
  2. Open the pen cap, check the expiry date, and check that the medication is clear (or pale yellow) and the pen itself is undamaged
  3. Wipe the red rubber seal area with an alcohol swab
  4. Attach a new needle to the pen
  5. Pull off the outer needle cap (set it aside) and remove the inner needle cap and discard it
  6. Slowly turn the dose selector knob until you hear it "click" twice and a dash appears in the dose window
  7. Hold the pen with the needle pointing up and gently tap the glass cartridge to allow any air bubbles to rise to the top
  8. Press the button to release the air bubble (priming)
  9. If no liquid appears after pressing, repeat steps 6-8 once more (do not repeat more than 2 times)

If, after following these steps, liquid still doesn't appear, please contact a pharmacist or specialist for further guidance.

Where You Can Inject the Mounjaro Weight-Loss Pen

You can choose to inject the Mounjaro weight-loss pen into an area with a layer of fat under the skin, such as:

  • The front of the thigh
  • The abdomen
  • The back of the upper arm


Steps for Injecting the Mounjaro Weight-Loss Pen

  1. Choose your injection site: Select the abdomen, thigh, or back of the upper arm, whichever is most convenient
  2. Prepare the dose: Turn the dose selector knob all the way until the -1 symbol appears in the dose window
  3. Start the injection: Insert the needle into the skin, then press the injection button all the way down. Hold the button and slowly count from 1 to 5 in your head before withdrawing the needle. Make sure the -0 symbol is showing clearly in the dose window before removing the needle
  4. Double-check: Withdraw the needle from the skin and check the -0 symbol once again. If it isn't showing yet, it means you haven't received the full dose — reinsert the needle at the same spot to finish delivering the remaining dose. Do not turn the dose selector again under any circumstances

After Injecting the Mounjaro Weight-Loss Pen

  • A small amount of bleeding at the injection site is normal — gently press a cotton ball or gauze on the area (do not rub or massage it) and apply a bandage if needed
  • Put the outer needle cap back on, twist the needle off the pen, and dispose of it safely in a sharps container
  • Close the cap on the Mounjaro weight-loss pen securely to keep it ready for next time