Estimate how much GLP-1 medication remains after the last dose, compare semaglutide and tirzepatide half-life timing, and see the usual washout milestones used to discuss Ozempic, Wegovy, Mounjaro, Zepbound, Saxenda, and Rybelsus.
Educational pharmacokinetic model This first-order elimination model explains timing concepts such as half-life, steady state, and washout. It does not decide when to stop, restart, switch, combine, or change a prescribed medicine.
Quick scenarios
Result
6.3% remaining after day 28
About 93.7% is eliminated under a simple first-order model for Wegovy (semaglutide 2.4 mg).
168h
Half-life
7 days
Half-life (days)
35 days
To steady state
30.3 days
95% eliminated
50%
Remaining at next scheduled dose
Concentration after stopping (Wegovy)
Day 0
100%
Day 7
50%
Day 14
25%
Day 21
12.5%
Day 28
6.3%
Day 35
3.1%
Day 42
1.6%
Selected checkpoint
6.3% remaining after 28 days
Elimination half-life
168 hours (7 days)
Steady-state reached (≈5 × t½)
35 days after starting
95% eliminated after stopping
30.3 days
99% eliminated after stopping
46.5 days
Usual dosing interval residual
50% remains after 7 days
Washout milestone
Remaining amount
Approximate timing
50% eliminated
50% remaining
7 days
75% eliminated
25% remaining
14 days
90% eliminated
10% remaining
23.3 days
95% eliminated
5% remaining
30.3 days
97% eliminated
3% remaining
35.4 days
99% eliminated
1% remaining
46.5 days
Clinical note First GLP-1 approved for chronic weight management in non-diabetic adults (2021).
Understanding the half-life of GLP-1 medications helps explain dosing frequency, time to steady state, and how long a drug remains in your system after stopping. This GLP-1 half-life calculator models the medication elimination curve for semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound), and liraglutide (Saxenda).
Why semaglutide and tirzepatide have weekly dosing
Semaglutide (Wegovy, Ozempic) has an exceptionally long half-life of ~7 days (168 hours), achieved through fatty acid modification that enables albumin binding — this slows renal filtration and enzymatic degradation. At a 7-day half-life, once-weekly dosing maintains relatively stable plasma concentrations. Tirzepatide (Zepbound, Mounjaro) has a half-life of ~5 days (120 hours), similarly supporting weekly dosing.
Liraglutide (Saxenda) has a much shorter half-life of ~13 hours, requiring daily injections. Despite similar mechanisms, the structural differences between GLP-1 receptor agonists produce markedly different PK profiles.
How long does Ozempic or Wegovy stay in your system?
Using the 5 half-life rule: semaglutide (7-day t½) reaches 95% elimination approximately 24 days after the last dose and 99% elimination in about 47 days. In practice, detectable semaglutide levels persist for 4–7 weeks post-injection.
Liraglutide (Saxenda) with its 13-hour t½ is essentially eliminated within 3–4 days. Tirzepatide (5-day t½) clears within approximately 17 days to 95% and 33 days to 99%.
Time to steady state
Steady-state plasma concentrations (within ~3% of true steady state) are reached after approximately 5 half-lives. For semaglutide (7-day t½), this is ~35 days (5 weekly injections). For tirzepatide (5-day t½), this is ~25 days. Weekly GLP-1 injections therefore achieve relatively stable plasma levels within 4–5 weeks.
How to use the GLP-1 half-life calculator
Choose the GLP-1 or GIP/GLP-1 medicine, then enter how many days have passed since the last dose. The result shows the estimated percentage remaining at that checkpoint, the percentage eliminated, the usual time to steady state, the 95% and 99% washout estimates, and the amount expected to remain at the next scheduled dose.
This makes the tool different from a simple article answer such as "Ozempic stays in your system for about five weeks." You can compare a 28-day semaglutide checkpoint with a 28-day tirzepatide checkpoint, see why Saxenda falls much faster, and use the washout milestone table to understand what 50%, 75%, 90%, 95%, 97%, and 99% elimination mean.
Remaining % = 100 × 0.5^(days since last dose ÷ half-life in days)
First-order elimination model used for the selected checkpoint and the visual concentration curve.
Eliminated % = 100 − remaining %
The calculator reports both perspectives because users often ask either how much remains or how much has cleared.
Steady state ≈ 5 × half-life
A practical rule for the time it takes repeated fixed dosing to approach the usual plateau.
Ozempic and Wegovy half-life: why five weeks is a practical answer
Semaglutide products such as Ozempic, Wegovy, and Rybelsus have an elimination half-life of about one week. After one week, a simple model leaves about 50% of the previous amount. After two weeks, about 25% remains. After five weeks, a little over 3% remains, which is why many clinical and pharmacy explainers use roughly five weeks as a practical "mostly out of your system" answer.
The calculator still shows a stricter 99% eliminated checkpoint because a small residual amount is not the same as zero. That distinction matters for people asking about stopping, side-effect duration, pregnancy planning, switching medicines, or why effects may taper gradually rather than stopping overnight.
Mounjaro and Zepbound half-life: tirzepatide clears faster than semaglutide
Tirzepatide products such as Mounjaro and Zepbound have a shorter half-life than semaglutide. Using a 5-day model, the 95% eliminated checkpoint arrives at about 22 days and the 99% eliminated checkpoint at about 33 days. The newer product label language describes an approximate 5- to 6-day half-life in studied obesity populations, so real timing may vary around the calculator's simplified midpoint.
That shorter tirzepatide half-life also changes the week-to-week residual pattern. After a 7-day dosing interval, less than half of a single tirzepatide dose remains under the simple model, while about half of a semaglutide dose remains. Repeated dosing still accumulates, so the single-dose residual number should not be mistaken for the total amount present after months of treatment.
Why the next-dose residual is useful
Many users are not only asking how long GLP-1 medication stays in the body after stopping. They also want to know why weekly injections still feel active near the end of the week, why appetite or side effects may fluctuate, or why a missed dose is not the same as having no medication on board. The next-dose residual estimate gives that context without pretending to provide dosing advice.
For weekly semaglutide, the model leaves about 50% of the prior dose after seven days. For weekly tirzepatide, the model leaves roughly 38% after seven days. For daily liraglutide, a 24-hour interval leaves a smaller residual because the half-life is only about 13 hours. Those residuals help explain dosing frequency and concentration stability.
What this GLP-1 washout model does not decide
A half-life calculator cannot decide whether you should stop a GLP-1, restart after a missed dose, delay surgery, plan pregnancy timing, manage side effects, or switch from semaglutide to tirzepatide. Those decisions depend on the indication, dose, duration of treatment, symptoms, blood glucose, pregnancy or contraception considerations, kidney or liver status, other medicines, and the product label.
The model also does not simulate repeated-dose accumulation, dose escalation, delayed absorption after injection, active metabolites, nausea severity, gastric-emptying effects, or weight regain after discontinuation. Treat the result as a pharmacokinetic explanation and a discussion aid for a prescriber or pharmacist, not as a medication instruction.
Worked example: semaglutide after 35 days
If the selected medicine is Wegovy or Ozempic and the days-after-last-dose field is set to 35, the calculator applies a 7-day half-life. Thirty-five days equals five half-lives. The remaining amount is therefore 100 × 0.5^5, or about 3.1%, so about 96.9% is eliminated under the simple model.
That example explains why "five half-lives" is a useful planning shorthand. It is close enough to mostly cleared for many educational discussions, but it is not literal zero and it is not a personalised medical clearance decision.
How this page differs from GLP-1 dose plotters
Full GLP-1 dose plotters can be useful when a user wants to enter dose size, dose dates, titration schedules, and repeated injections. They can also become easy to overinterpret because a plotted amount is not the same as a clinical effect, side-effect risk, or prescribing decision.
This page focuses on the narrower half-life and washout question. It gives a fast, transparent concentration curve, a custom checkpoint, steady-state timing, next-dose residual context, and a milestone table that can be read without entering personal medication history. That makes it useful for quick education, while the limitations make clear when a prescriber or pharmacist is the right source.
Frequently asked questions
How long after stopping Ozempic until it is out of my system?
Semaglutide (Ozempic/Wegovy) has a ~7-day half-life. At 5 half-lives (~35 days), 97% is eliminated. At 99% elimination (47 days), only trace amounts remain. Most clinical effects wear off noticeably within 2–4 weeks of the last dose, and weight regain typically begins within weeks of stopping.
Why does Saxenda need to be injected daily but Wegovy is weekly?
Liraglutide (Saxenda) has a ~13-hour half-life and is cleared rapidly. Semaglutide (Wegovy) has been modified with fatty-acid conjugation to bind albumin, extending its half-life to ~7 days. This structural difference is what enables weekly dosing.
What is the half-life of Ozempic and Wegovy?
Ozempic and Wegovy both contain semaglutide, which has an elimination half-life of about one week. That means a simple first-order model leaves about half of the previous amount after seven days, about one quarter after two weeks, and about 3% after five weeks.
What is the half-life of Mounjaro and Zepbound?
Mounjaro and Zepbound both contain tirzepatide. This calculator uses a 5-day half-life model, while current prescribing information describes an approximate 5- to 6-day half-life in studied obesity populations. Under a 5-day model, 95% elimination is about 22 days and 99% elimination is about 33 days.
Does half-life tell me when side effects will stop?
Not exactly. Half-life estimates how quickly the amount in the body declines, but symptoms depend on dose, duration of treatment, hydration, food intake, blood glucose, other medicines, and individual sensitivity. Persistent vomiting, dehydration, severe abdominal pain, faintness, or concerning symptoms should be reviewed clinically rather than interpreted through a calculator alone.
Can I use this to plan pregnancy timing after GLP-1 medication?
Use the calculator only to understand washout math. Pregnancy planning depends on the exact medicine and product guidance. Semaglutide and tirzepatide labels include specific discontinuation timing before planned pregnancy, so a prescriber should interpret that guidance for the individual situation.
Why does the calculator show 95% and 99% eliminated?
Different sources use different practical thresholds. Five half-lives leaves a little over 3% remaining, 95% eliminated leaves 5% remaining, and 99% eliminated leaves 1% remaining. Showing several milestones avoids the misleading idea that a medicine is suddenly either fully present or completely gone.
Does this model account for weekly dose build-up?
No. The visible curve is a single-dose elimination model after stopping. Repeated weekly dosing accumulates toward steady state, usually over about 4 to 5 half-lives, so the total amount present after months of treatment can be higher than the residual from one recent dose alone.
Why can I still feel effects near the end of a weekly dosing interval?
Long half-life medicines decline gradually. With semaglutide, about half of a single dose remains after seven days under the simple model. With tirzepatide, a meaningful amount also remains at day seven. Prior doses may still contribute as well, especially after steady state is reached.
Can I flush Ozempic, Wegovy, Mounjaro, or Zepbound out faster?
There is no reliable way to quickly flush these medicines out of the body. The amount falls according to pharmacokinetics, and severe or persistent side effects should be managed with medical advice rather than attempting home clearance strategies.
Is Rybelsus half-life different from injectable semaglutide?
Rybelsus is oral semaglutide, so the semaglutide molecule still has a long elimination half-life of about one week. The route and bioavailability differ from injection, but the washout concept is still much closer to weekly semaglutide than to daily liraglutide.
Can I use this calculator for compounded GLP-1 products?
The calculator is based on named medication half-life values and does not verify compounded product identity, concentration, dosing accuracy, or release behaviour. If the medicine is not an FDA-approved product or the dose history is unclear, ask a qualified clinician or pharmacist before drawing practical conclusions from a half-life estimate.
