Missed a Tirzepatide Dose? What to Do and Why It Matters

What happens pharmacokinetically when you miss a dose

Tirzepatide has a ~5-day half-life with once-weekly dosing. At steady state (reached after ~5 weeks), active concentrations sit at a plateau between weekly injections — each new dose replaces exactly what cleared since the last dose.

When you miss a dose, the clearance clock keeps running but no replacement dose arrives. By the time you're 2 weeks from your last injection:

• After 7 days (1 missed dose): ~50% of steady-state trough remaining
• After 10 days: ~35% remaining
• After 14 days (2 weeks from last dose): ~25% remaining

The practical consequence: appetite suppression fades noticeably within 7–10 days after a missed dose, because active concentrations drop below the therapeutic threshold for many users.

The 5-day rule: prescribing guidance

FDA-approved labeling for tirzepatide (Zepbound/Mounjaro) provides the following missed dose guidance:

• If fewer than 4 days (96 hours) have passed since the scheduled injection: take the missed dose as soon as possible. Resume weekly dosing from the new injection date.
• If 4 or more days have passed since the scheduled injection: skip the missed dose. Wait and take your next dose on the regularly scheduled day.

The 4-day cutoff prevents inadvertently doubling up — if you're close to your next scheduled dose, taking the missed one would create two doses within a few days, which could significantly increase GI side effects.

Semaglutide missed dose: the same framework

Semaglutide (Wegovy/Ozempic) has a ~7-day half-life. Prescribing labeling:

• If fewer than 5 days have passed: take the missed dose.
• If 5 or more days have passed: skip it and resume the regular schedule.

The longer half-life gives semaglutide a slightly longer window before skipping becomes necessary.

After missing a dose: GI side effects on resumption

A commonly reported experience: resuming a GLP-1 after a 1–2 week gap produces stronger GI side effects than had been experienced at that dose during steady state. This is pharmacokinetically expected — concentrations dropped below steady state, and resuming the full maintenance dose produces a steeper rise than the gradual accumulation pattern your body adapted to.

Some providers instruct patients to step back one dose level after a gap of 2+ weeks, then re-escalate. This is a protocol design decision for your prescribing provider — don't self-adjust dose levels after a gap without checking with them.

If you've missed multiple doses

After a gap of 4+ weeks (approximately 5 half-lives), you're effectively starting over pharmacokinetically. Some providers restart the escalation protocol from the beginning or from a lower step. Others resume the previous maintenance dose with awareness that GI side effects may recur temporarily.

The reason to flag multi-week gaps to your provider: GI side effect tolerance developed during initial escalation is not permanent. It reflects adaptation to sustained drug levels. After a full washout, that adaptation resets.

Why logging injection dates prevents this problem

"I think I missed last week's dose but I'm not sure" is a common clinical conversation that a dose log eliminates. My Pep Calc records each injection with date, dose, and site — so you always have an accurate record of when the last injection was, enabling the correct missed-dose decision (under 4 days → inject now; over 4 days → skip).

The half-life chart shows the active concentration curve from your actual logged doses. A missed dose shows up as a visible concentration drop in the chart — useful context for your provider during clinical visits.