Where and how to inject Zepbound and Mounjaro, in the words of the instructions

Where the instructions say to inject

“Your healthcare provider can help you choose the injection site that is best for you. You or another person can inject the medicine in your stomach (abdomen) or thigh.” “Another person should give you the injection in the back of your upper arm.” “Change (rotate) your injection site each week.” “You may use the same area of your body but be sure to choose a different injection site in that area.”

That is step 1 of the single-dose pen instructions, and the Zepbound and Mounjaro documents print it in the same words. The KwikPen instructions say the same thing with one extra detail: the stomach injection goes “at least 2 inches from the belly button”.

The vial instructions add the reason for rotating, and a list of places to avoid: change the site within the area you choose for each dose “to reduce your risk of getting lipodystrophy (pits in skin or thickened skin) and localized cutaneous amyloidosis (skin with lumps)”, and do not inject where the skin is pitted, thickened, lumpy, “tender, bruised, scaly or hard, or into scars or damaged skin”. The same page says not to inject tirzepatide into the site used for another medicine, and not to mix it with any other medicine.

The single-dose pen, step by step

The single-dose pen is the device most prescriptions arrive in, and its instructions run to four steps once the site is chosen. The wording below is Zepbound’s; Mounjaro’s document is the same, with its own product name and a capital P on Pen.

1. Pull off the gray base cap. “Make sure the pen is locked. Do not unlock the pen until you place the clear base on your skin and are ready to inject.” The cap goes in the trash and not back on the pen, and the instructions say not to touch the needle.
2. Place the clear base flat against your skin at the injection site, then unlock the pen by turning the lock ring.
3. Press and hold the purple injection button for up to 10 seconds. The document gives two: “First click = injection started”, then “Second click = injection completed”.
4. Check that it worked. “You will know your injection is complete when the gray plunger is visible.” The pen then goes into a sharps container.

The instructions answer a few things people worry about, in their own words: “Air bubbles are normal”; a drop of liquid on the needle tip is normal too; it is “not necessary to warm the pen to room temperature”; and some people hear a soft click before the second loud one, which is the pen working. If the gray plunger is not visible afterward, the document says to contact Lilly rather than to guess, and to store the pen safely until then.

The KwikPen, and the vial and syringe

Two other devices carry the same drug, and they are not used the same way.

The KwikPen holds four weekly doses and is primed before each one, which the single-dose pen never needs: “Prime before each weekly injection. Priming removes air from the cartridge and makes sure that your Pen is working correctly.” A new pen needle goes on every week, the dose knob is turned “all the way until it stops” rather than counted in clicks, and the injection ends with the icon showing in the dose window. After four doses the pen is discarded “including the unused medicine”, and the instructions say not to transfer tirzepatide from the pen into a syringe.

With a vial, the syringe and needle are not supplied. The instructions say to use a new syringe and needle for every injection, and they set the dose by volume: draw 0.5 mL of air in, put it into the vial, turn the vial upside down and draw past the 0.5 mL line, then push back up to it. On the injection itself the document is brief: insert the needle, push the plunger down, and “the needle should stay in your skin for at least 5 seconds to make sure you have injected all of your dose”. Do not recap the needle afterward.

What to check before injecting

Every one of these documents opens with the same checks. Look at the label to confirm the medicine and the dose and that it has not expired; look at the pen or vial for damage; and look at the liquid itself. The instructions describe what it should be: not frozen, not cloudy, “colorless to slightly yellow”, with no particles in it. Then wash your hands.

The KwikPen list is blunter about when to stop: do not use it if the medicine name or dose strength does not match the prescription, if the pen is expired or looks damaged, or if the medicine has been frozen or has particles in it. A pen that has been dropped on a hard surface is not used either.

Where the medicine is kept before any of that is section 16 of each label, set out on refrigeration and storage; the day of the week the injection belongs to, and what the labels say when it is missed, is on missed dose rules.

What the instructions do not say

Three questions readers arrive with are not answered in these documents, and the honest answer is that they are for a prescriber or a pharmacist rather than for a website.

• Whether to pinch the skin. The vial instructions say only that “Your healthcare provider should tell you if you should pinch the skin before injecting”. The pen instructions do not raise it at all.
• Which needle to use with a vial. The needle and syringe are not supplied, and the document points at the prescriber: use, for example, “a 1 mL syringe and needle as recommended by your healthcare provider”.
• What to do about a dose you are unsure of. Both pen documents send the reader to the manufacturer’s number rather than to a rule of thumb, and the KwikPen instructions say plainly not to start over or repeat an injection.

Every device also comes with diagrams beside each step, and this page has none of them. The Instructions for Use for the pen, the KwikPen and the vial are printed in full with each label, and both labels are linked below.

Sources

Zepbound’s pen instructions carry their own revision date, April 2026, inside a label whose own effective date is 2026-08-28; Mounjaro’s label is effective 2026-08-27. Open the label itself for the diagrams.

See the providers

The device a prescription arrives in is set by what is dispensed, not by the seller’s marketing. The boards list who sells tirzepatide and what each one publishes.

• Tirzepatide providersprovider board

  Readers who have settled on tirzepatide and are choosing who to buy it from.

• Semaglutide providersprovider board

  Readers who have settled on semaglutide and are choosing who to buy it from.

More, read from the same labels

• Semaglutide vs tirzepatidereading the label

  What the four FDA-approved labels say each molecule is, what each is approved to treat, and where the two differ.

• How they workreading the label

  The receptor each molecule switches on, what the labels say that does to appetite, blood sugar and the stomach, and why one dose lasts a week.

• Is Ozempic insulin?reading the label

  What the Ozempic label calls semaglutide, how that differs from insulin, and where insulin appears on these labels as a separate medicine.

• Zepbound vs Ozempicreading the label

  Four brand names, two molecules and two kinds of approval: which of these products are the same drug, and what each one is actually approved to do.

• Dose escalation schedulesreading the label

  The starting dose, the escalation interval and the maximum dose each label sets, and why they are not interchangeable.

• Side effect ratesreading the label

  What each label reports for nausea, vomiting, diarrhea and constipation — and the sentence every label prints above those numbers.

• Hair lossreading the label

  Which labels report hair loss, the rate against placebo where a trial measured it, and why two of them put no number on it.

• Fatigue and tirednessreading the label

  Which labels list fatigue, the rate against placebo where a trial measured it, and what each label counts as fatigue.

• Missed dose rulesreading the label

  The window each label gives for a late dose, and the minimum gap it requires when the injection day changes.

• Drug interactionsreading the label

  Insulin and sulfonylureas, oral medications, and the oral-contraceptive precaution that appears on two of these four labels and not the other two.

• Buying one onlinereading the label

  The agency's own warning signs for a telehealth GLP-1 seller, its 28-day vial rule, and what it says about drugs that arrive warm.

• Zepbound by dosereading the label

  What each Zepbound dose achieved in the trials printed in its label, what the label says about choosing a maintenance dose, and what the higher doses cost in side effects.

• Zepbound at 3 monthsreading the label

  What the Zepbound label reports and at which weeks it reports it, and where the label's own dose schedule puts a reader at three months.

• Refrigeration and storagereading the label

  How cold each pen is kept, how many days it can spend at room temperature, and what the labels say about heat and freezing.

• Who should not take onereading the label

  The boxed warning every one of these labels carries, the two contraindications, and which warnings appear on which product.