Usually very little. The Ozempic label says to take a missed dose within 5 days [1]. After 5 days, skip it and inject on the regular day. Semaglutide has a half-life of about 1 week [2]. Half of the last dose is still circulating 7 days later. In a simulation, taking 80% of doses kept about 90% of the weight loss [5].
So one late dose inside the window is mostly a scheduling problem. Two or more in a row is different. That case is covered in how to restart a GLP-1 after stopping.
The rule on each label
Each label sets its own window. They are not interchangeable.
Ozempic: take the dose as soon as possible within 5 days after the missed dose [1]. If more than 5 days have passed, skip it. The next dose goes on the regularly scheduled day.
Wegovy injection: the test is the gap to the next dose [3]. If that dose is more than 2 days away, inject now. If it is less than 2 days away, skip the missed dose.
Zepbound: take the dose within 4 days, or 96 hours [4]. After 4 days, skip it. Two Zepbound doses must also sit at least 3 days, or 72 hours, apart.
On a 7-day cycle the Ozempic and Wegovy rules land in the same place. Five days late leaves 2 days to the next dose. The Zepbound cutoff is a day earlier.
Why a week-long half-life buys time
Half-life is the time for half the drug to clear. For Ozempic, the label gives about 1 week [1]. It adds that semaglutide stays in circulation for about 5 weeks after the last dose.
A trial in healthy Japanese and Caucasian men measured the same thing [2]. Accumulation matched a half-life of about 1 week and a weekly dosing interval. Weekly dosing builds a steady level. One late dose dents that level. It does not empty it.
Tirzepatide clears faster. The Zepbound label puts its half-life at about 5 to 6 days in people with overweight or obesity [4]. That is one reason its window is shorter.
The Hero figure shows the arithmetic at a 7-day half-life. About 61% of the last dose remains on day 5. That is a calculation from the label, not a measured blood level.
What missed doses cost in weight
One study modeled the question directly [5]. It used validated pharmacokinetic and pharmacodynamic models of semaglutide and tirzepatide. Simulated patients missed doses at random.
Taking 80% of prescribed doses yielded around 90% of the weight loss of perfect adherence [5]. Put another way, 80% adherence kept around 90% of the loss versus nearly 70% at 50% adherence. Body weight fluctuated only slightly, as long as patients did not miss more than several doses in a row.
The limit is plain: these are simulated patients. The result comes from a model, not from people who skipped doses in a trial. The authors’ own conclusion is that the common 80% adherence threshold needs revision.
What a skipped dose does to the bill
A skipped dose is not lost. It stays in the pen or the carton for the next scheduled day. The supply stretches by one week.
One limit applies to multi-dose pens. After first use, an Ozempic pen may be kept for 56 days [1]. A pen that sits unused for a week still counts those days.
The larger cost is a restart. Restarting at a lower dose can mean buying a starter strength again. What each strength costs across sellers is in how much a GLP-1 costs per month.
Missing a dose on purpose
Skipping weeks on purpose to stretch a supply is a separate question. No trial has tested an every-other-week schedule. That gap is covered in whether a GLP-1 can be taken every two weeks.
Moving the injection day is allowed under the labels, within limits. Ozempic needs at least 2 days between doses [1]. Zepbound needs at least 3 [4]. The choice of day is covered in what day to take a weekly GLP-1 shot.
For what happens to weight after a full stop, see the pooled regain data across 17 studies.