Mounjaro uses a prefilled, single-dose pen that you inject under the skin once a week. The process takes about 10 seconds of actual injection time, and the pen does most of the work for you. Here’s a complete walkthrough of preparation, injection technique, and what to do afterward.
Choose Your Injection Site
You have three options for where to inject Mounjaro: your abdomen, the front of your thigh, or the back of your upper arm. The upper arm is the one spot where you’ll likely need someone else to help, since it’s hard to reach and position the pen correctly on your own.
If you’re using your abdomen, pick a spot at least two inches away from your belly button. Avoid any area where the skin is tender, bruised, red, or hard. Rotate your injection site each week. Using the same spot repeatedly can cause the fat tissue underneath to thicken or shrink, which affects how well the medication absorbs and can create visible lumps under the skin. A simple approach: if you injected in your left thigh this week, use your right thigh or abdomen next week.
Prepare the Pen
Mounjaro pens are stored in the refrigerator between 2°C and 8°C (about 36°F to 46°F). Injecting cold medication can sting more, so take the pen out and let it sit at room temperature for about 30 minutes before you use it. If you prefer, you can store an unused pen at room temperature (up to 30°C or 86°F) for up to 30 days, which means your next dose is always ready to go without the wait.
Before injecting, look at the liquid through the pen window. It should be clear and colorless to slightly yellow. If it looks cloudy, discolored, or has particles floating in it, don’t use that pen. Also check the expiration date printed on the label.
Step-by-Step Injection Process
Once your pen is at room temperature and you’ve chosen a clean injection site, you’re ready to go.
- Remove the gray base cap. Pull it straight off. You’ll see the needle is already attached and hidden inside the pen, so you won’t see or handle a bare needle at any point.
- Position the pen. Place the flat gray base firmly against your skin at the injection site. Don’t pinch the skin unless your healthcare provider has specifically told you to.
- Unlock and press. Twist the clear lock ring to unlock the pen, then press and hold the purple injection button. You’ll hear a loud click, which means the injection has started.
- Hold for 10 seconds. Keep the pen pressed flat against your skin. The medication is being delivered during this time. Don’t lift the pen early.
- Check for the gray plunger. The injection is complete when the gray plunger becomes visible in the pen window. This is your confirmation that the full dose was delivered.
- Remove the pen. Lift the pen straight off your skin. The needle retracts automatically and locks into the pen body, so you can’t accidentally stick yourself afterward.
What to Do After Injecting
If you see a small drop of blood at the injection site, lightly press a cotton ball or piece of gauze against it. Don’t rub the area, as rubbing can increase bruising and irritation. A tiny drop of blood or even a small drop of medication on the skin surface is normal and doesn’t mean the dose failed, as long as the gray plunger was visible in the window.
Place the used pen in a sharps disposal container immediately. Don’t throw it in your regular household trash, even though the needle retracts. If you don’t have a sharps container yet, you can purchase one at most pharmacies, or check with your local health department about drop-off locations, mail-back programs, or special waste pickup services. Fill the container no more than three-quarters full before disposing of it, and keep it out of reach of children and pets. If you’re traveling, carry a small travel-size sharps container with you.
Dosing Schedule and Timing
Mounjaro starts at 2.5 mg once weekly. This initial dose is designed to let your body adjust to the medication and isn’t the therapeutic dose. After four weeks at 2.5 mg, you’ll move up to 5 mg. From there, your prescriber may increase your dose in 2.5 mg increments, with at least four weeks between each step up. This gradual approach reduces the nausea, diarrhea, and other GI side effects that are common with this class of medication.
Pick a day of the week that works for you and inject on that same day each week. You can give yourself the injection at any time of day, with or without food. If you miss a dose, take it as soon as you remember, then adjust your schedule so your next dose falls at least three days later. If it’s been too long since your missed dose, skip it entirely and resume on your regular day the following week.
Storage at a Glance
Unused pens belong in the refrigerator. If you need to, you can keep an unused pen at room temperature (up to 86°F / 30°C) for a maximum of 30 days. After 30 days at room temperature, discard it even if there’s medication left. Once you’ve used a pen for a dose, you can store it at room temperature for up to 30 days as well, though since each pen contains only a single dose, you’ll typically dispose of it right after injection. Never freeze Mounjaro, and don’t use a pen that has been frozen.
Tips for a More Comfortable Injection
The most common complaint is stinging during injection, which letting the pen warm to room temperature largely solves. If you’re still finding it uncomfortable, try rotating to a fattier area of your abdomen or thigh, where there are fewer nerve endings close to the surface. Some people find that pressing the pen firmly against the skin before triggering the injection reduces the sensation, since the pressure slightly numbs the area.
Mild redness, itching, or a small bump at the injection site can last a day or two and is not a cause for concern. If redness spreads, the area feels warm and swollen, or you develop a rash that extends beyond the injection site, that’s worth reporting to your prescriber, as it could signal a localized reaction that needs attention.