Drug facts

A missed dose

Reviewed August 2026

Quick answer

The label’s rule is a deadline, not a judgment call. If a dose is missed, it is taken as soon as possible within 4 days (96 hours) of the missed dose. If more than 4 days have passed, that dose is skipped and the next one is taken on the regularly scheduled day. Either way, the regular once-weekly schedule then resumes.

The rule, as written1

Section 2.3 is short enough to state without paraphrase. It instructs that if a dose is missed, patients administer the product as soon as possible within 4 days (96 hours) after the missed dose; that if more than 4 days have passed, the missed dose is skipped and the next dose administered on the regularly scheduled day; and that in each case patients can then resume their regular once-weekly dosing schedule.

Section 2.3, in table form

Within 4 days
Take the missed dose as soon as possible.
More than 4 days
Skip it. Take the next dose on the regular day.
Afterwards
Resume the regular once-weekly schedule.

Note what the rule does not say. It does not say to double the next dose, and it does not say to restart the escalation from the beginning. It also does not change the size of any dose — the schedule of strengths and the four-week steps between them are a separate matter, set out in the approved dosing schedule and its four-week steps.

Moving your weekly day1

The same section covers the related question. The day of weekly administration can be changed if necessary, as long as the time between the two doses is at least 3 days (72 hours). That 72-hour floor is the constraint; the day of the week itself is not.

Why four days and not a week2

The pharmacokinetics section reports an elimination half-life of approximately 5 to 6 days in patients with overweight or obesity, and steady-state concentrations reached after 4 weeks of once-weekly administration. A drug that clears that slowly is still substantially present several days after a missed injection, which is the context in which a 96-hour window and a 72-hour minimum gap make sense as written. The underlying pharmacology is covered in what tirzepatide does and how long it stays in the body.

A compounded vial has no rule of its own3

On the label — Mounjaro / Zepbound

Supplied with FDA-approved prescribing information and a Medication Guide, and dispensed as a specific presentation — vial, single-dose pen, autoinjector or KwikPen — that patients and caregivers are trained on before initiation.

In a compounded vial

Not established.

Nothing on this page was written about a compounded preparation, because no approved labeling exists for one. If your vial came from a compounding pharmacy, the instructions that govern it are the ones your prescriber gave you and the ones printed on the label the pharmacy attached. Where those and this page differ, theirs is the document that applies to the thing in your fridge — and how that vial should be kept between doses is its own question, covered in storage and the beyond-use date on a compounded vial.

Sources

  1. FDA prescribing information for ZEPBOUND (tirzepatide), section 2.3 Recommendations Regarding Missed Dose, revision 4/2026 DailyMed
  2. FDA prescribing information for ZEPBOUND (tirzepatide), section 12.3 Pharmacokinetics, revision 4/2026 DailyMed
  3. FDA prescribing information for ZEPBOUND (tirzepatide), section 2.4 Important Administration Instructions, revision 4/2026 DailyMed