How to use a Zepbound or Mounjaro pen

Zepbound and Mounjaro come in two kinds of pen, and they work differently. The single-dose pen holds one weekly dose with the needle already inside: you place it on your skin, unlock it, and press and hold the button until the second click. The KwikPen holds 4 weekly doses: you attach a new pen needle, prime it, turn the dose knob all the way, and hold the knob in for a slow count of 5. The steps below come from the official Instructions for Use (IFU) on DailyMed, which are the same for both brands apart from the name.

A pen sets the dose for you, so there are no units to work out. What you do choose each week is where to inject: the injection site rotation planner keeps track so you don’t land on the same spot twice in a row.

The two pens side by side

Both labels ask your care team to tell you which presentation you’ll get, train you on that one, and point you to the new IFU if your prescription switches presentation (Zepbound section 2.4, Mounjaro section 2.2). The habits from one pen don’t carry over to the other.

Sources: Zepbound label sections 3, 11 and 16.2 and its single-dose pen and KwikPen IFUs; the Mounjaro label and IFUs match (Zepbound, Mounjaro). The strength on your pen is the dose your prescriber chose; the labels set the schedule, so follow your prescriber.

Before you inject (both pens)

The labels say to inject once a week, “any time of day, with or without meals,” under the skin only. Then check the pen:

• Right medicine and dose. The name and strength on the pen match your prescription, and it hasn’t expired.
• Not damaged. The single-dose pen “has glass parts.” If you drop it on a hard surface, don’t use it.
• The liquid looks right. The labels say it “should appear clear and colorless to slightly yellow.” Don’t use it if it’s cloudy, discolored, has particles, or has been frozen.
• Clean hands. Wash your hands before you start; the KwikPen IFU says with soap and water.

You don’t need to warm a single-dose pen first: the IFU says “It is not necessary to warm the pen to room temperature.” Air bubbles in it are normal (Zepbound IFU).

Where to inject

Both IFUs give the same three areas: you or another person can inject into your stomach (abdomen) or thigh, and another person can inject into the back of your upper arm. The KwikPen IFU adds: stay “at least 2 inches from the belly button.” Change the spot every week; the single-dose pen IFU says “You may use the same area of your body but be sure to choose a different injection site in that area.” Your healthcare provider can help you pick the site that suits you. For how to plan a rotation, see subcutaneous injection sites.

If you also use insulin with Mounjaro, the label says to give them as separate injections and never mix them. You may use the same body region, “but the injections should not be adjacent to each other” (Mounjaro label, section 2.2).

Using the single-dose pen

Take the pen out of the refrigerator, and leave the gray base cap on until you’re ready to inject.

1. Choose your injection site

   Pick a spot on your stomach or thigh, or on the back of your upper arm if someone else is injecting. Use a different spot from last week.

2. Pull off the gray base cap

   Make sure the pen is locked first. Pull the cap straight off and put it in your household trash. Don’t put it back on, as that “could damage the needle,” and don’t touch the needle.

3. Place the clear base flat on your skin, then unlock

   Put the clear base flat against your skin at the site. Only then unlock the pen by turning the lock ring. Don’t unlock it before the base is on your skin.

4. Press and hold for up to 10 seconds

   Press and hold the purple injection button. The first click means the injection has started; the second click means it’s done. Your injection is complete when you can see the gray plunger.

Steps from the single-dose pen IFU in the Zepbound and Mounjaro labels (revised April 2026).

What the clicks mean

There are two loud clicks: the first starts the injection, the second finishes it. Some people hear a soft click just before the second loud one; the IFU calls that “the normal operation of the pen. Do not remove the pen from your skin until you hear the second loud click.” You don’t have to keep the button pressed the whole time, but the IFU says holding it “may help you keep the pen steady against your skin.”

If you don’t see the gray plunger afterward, the IFU says to contact Lilly at 1-800-545-5979 (1-800-Lilly-Rx) for instructions. A drop of liquid on your skin afterward is normal: press a cotton ball or gauze on the spot, and don’t rub it.

Using the KwikPen

You’ll need a new KwikPen-compatible pen needle (not included), an alcohol swab, and gauze or a cotton ball. The pen has 4 weekly doses; prime it before every one.

1. Prepare the pen

   Wash your hands with soap and water and pull the pen cap straight off. Check that the medicine name and strength match your prescription, the pen hasn’t expired or been damaged, and the medicine hasn’t been frozen, isn’t cloudy or discolored, and has no particles. Wipe the red inner seal with an alcohol swab.

2. Attach a new pen needle

   Push the capped pen needle straight onto the pen and twist until it’s tight. Pull off the outer needle shield and keep it, because you’ll use it again. Pull off the inner needle shield and put it in your household trash.

3. Prime the pen

   Slowly turn the dose knob until you hear 2 clicks and the extended line shows in the dose window. Hold the pen with the needle pointing up and tap the cartridge holder gently so air bubbles rise. Push the dose knob in until it stops and slowly count to 5, releasing medicine into the air, not into your body. You’re primed when a drop comes out of the needle tip.

4. Pick the injection site for this dose

   Thigh or stomach, at least 2 inches from your belly button, or the back of your upper arm if someone else injects. Change the site each week.

5. Select your weekly dose

   Turn the dose knob all the way until it stops and the icon is in the dose window. That’s your weekly dose. The IFU says: “Do not count clicks as you select the dose.”

6. Inject and hold for a count of 5

   Insert the needle into your skin. Push the dose knob in until it stops, then slowly count to 5 while holding it. The icon must show in the dose window before you take the needle out.

7. Check, then put the pen away

   If you see the icon in the dose window, you’ve received the full dose, and a drop on the needle tip is normal. Press gauze lightly on the site if it bleeds; don’t rub. Carefully replace the outer needle shield, remove the needle, and replace the pen cap. Don’t store the pen with a needle on it, since that can cause leaking, a blocked needle and air in the pen.

Steps from the KwikPen IFU in the Zepbound and Mounjaro labels (revised January 2026). The IFU states the pen “meets the current dose accuracy and functional requirements of ISO 11608-1.”

When the KwikPen doesn’t behave

• No drop when priming. Repeat the priming step no more than 2 more times. Still nothing: change the pen needle and prime no more than 1 more time. Then contact Lilly.
• The icon isn’t in the window after injecting. Put the needle back into your skin and finish the injection. Don’t redial the dose. If you still think you missed part of it, the IFU says “do not start over or repeat the injection”; call your prescriber or pharmacist.
• The dose knob is hard to push. Push more slowly. If it’s still hard, the needle may be blocked: put on a new pen needle and prime again.
• The knob won’t turn to a full dose. Throw the pen away, including the medicine left in it: “There may not be enough medicine left in the pen to give a full dose.”

After the fourth dose

The pen stops you from dialing a full dose once you’ve given 4 weekly doses. Throw it away then, even with medicine left. Don’t transfer it into a syringe, and don’t try to inject what’s left: the IFU says that “could result in an incomplete dose even though the Pen still has medicine left in it.” An opened KwikPen also goes after a total of 30 days at room temperature or 30 days after first use, whichever comes first (label section 16.2).

Who shouldn’t inject alone

• Vision problems. Both labels say the KwikPen “is not recommended for self-administration by those who are visually impaired.” The single-dose pen IFU says not to use the pen without help from a person trained to use it.
• Children on Mounjaro. The Mounjaro label says its KwikPen “is not recommended for self-administration by pediatric patients” (section 2.2).

Storage and disposal

Both pens go in the refrigerator at 2 °C to 8 °C (36 °F to 46 °F), in the original carton, and never in the freezer. A single-dose pen may stay out at up to 30 °C (86 °F) for a total of 21 days; a used KwikPen may be kept at room temperature up to 30 °C (86 °F) between doses (Zepbound label, section 16.2 and IFUs). For trips and time out of the fridge, see storing GLP-1 pens and traveling.

The IFUs say to put used sharps in an FDA-cleared sharps disposal container right away, not in household trash, and not to recycle the container. The single-dose pen goes in whole. No FDA-cleared container? The IFUs accept a heavy-duty plastic household container with a tight, puncture-resistant lid that stays upright, doesn’t leak and is labeled as hazardous waste. For what to do with it when it’s full, see sharps disposal.

Common mistakes

• Unlocking the single-dose pen before it’s on your skin. Place the clear base flat first, then turn the lock ring.
• Lifting the pen at the first click. The injection has only started. Wait for the second loud click and the gray plunger.
• Skipping the KwikPen prime. The IFU says to prime before each weekly injection; it removes air and checks the pen works.
• Counting KwikPen clicks to set a dose. The pen gives one fixed dose: turn the knob all the way. The IFU says not to count clicks.
• Reusing a pen needle or leaving it on the KwikPen between doses.
• Using the same spot every week. Rotate within the area, and keep Mounjaro and insulin injections apart.

Questions people ask