How the calculator works
Every drug leaves the body at a rate described by its elimination half-life: the time it takes for the amount in your blood to drop by half. Semaglutide, the molecule in Ozempic and Wegovy, has a half-life of about 7 days. Tirzepatide, the molecule in Zepbound and Mounjaro, clears faster at about 5 days. Older daily liraglutide (Saxenda) is gone in roughly 3 days.
The long half-lives are not an accident. They are the entire reason these drugs work as weekly injections: the molecule was engineered to bind to albumin in your blood and hide from clearance, keeping appetite suppression continuous between doses. The same engineering means the exit is slow and quiet. There is no last-dose cliff. There is a fade.
The standard clinical rule of thumb is that a drug is essentially cleared after five half-lives: about 5 weeks for semaglutide, about 25 days for tirzepatide. The curve above applies that math to your actual last dose date.
Semaglutide vs tirzepatide: the two-week difference
| Molecule | Brands | Half-life | 50% gone | Essentially cleared |
|---|---|---|---|---|
| Semaglutide | Ozempic, Wegovy, Rybelsus, most compounds | ~7 days | ~1 week | ~5 weeks |
| Tirzepatide | Zepbound, Mounjaro, compounded tirz | ~5 days | ~5 days | ~25 days |
| Liraglutide | Saxenda, Victoza | ~13 hours | ~13 hours | ~3 days |
The practical consequence: Zepbound and Mounjaro users feel the transition about a week earlier than Ozempic and Wegovy users. If you are comparing notes with someone on a different molecule, your timelines will not line up, and neither of you is doing it wrong.
Why week one feels like nothing happened
Week one, explained before it happens
The scale will jump. It is not fat.
Typical range is 2 to 6 lb. Four shown as an example.
A week after your last semaglutide dose, roughly half the drug is still circulating. Appetite suppression is still meaningfully active. This is the most misunderstood part of stopping: people expect a withdrawal moment, feel fine for ten days, conclude they are one of the lucky ones, and then get ambushed in week three when the level finally drops below the threshold where they feel it.
The week 1 scale jump. Almost everyone sees the scale rise 2 to 6 lbs in the first two weeks off. It is water and glycogen, not regained fat. Fat regain requires a sustained calorie surplus over weeks. If you know the jump is coming, it is a data point. If you do not, it can feel like proof that everything is already falling apart. It is not.
What the fade actually feels like, week by week
Pharmacokinetics set the schedule, and thousands of community reports describe the experience. The two line up remarkably well:
- Week 1: drug still substantially active. False confidence is common. The water-weight jump lands here.
- Weeks 2-3: portions stop self-limiting. Satiety gets shorter. The first flickers of food noise return, often as idle thoughts about specific foods.
- Weeks 3-6: the hard zone. Appetite hormones rebound and hunger can temporarily run above your pre-drug baseline, aimed at a body that now burns several hundred fewer calories a day than it did before the weight loss. This is where most regain starts.
- Months 2-6: the regain window documented in the trials. In the STEP-1 extension, people who stopped semaglutide regained about two-thirds of their lost weight within a year, without structured support. That number is the argument for having a plan, not a prophecy.
The counterweight matters just as much: in Cleveland Clinic real-world data from roughly 8,000 discontinuers, about 45% maintained or kept losing at one year. Maintainers exist at scale. The difference is behavior and support, not luck.
What changes the timeline
- Your dose when you stopped. Stopping from 15mg of Zepbound is a taller cliff than stopping from 5mg. Lower final doses mean a gentler fade.
- Tapering. Stepping down before stopping lowers the height you fall from, spreading the appetite transition over months instead of weeks. Whether that improves long-term weight outcomes is still unproven in trials, though many clinicians favor it. Dose changes are a prescriber conversation.
- Time on the drug. Longer use means steadier levels and, often, more lost weight to defend, which raises the stakes of the transition without changing its speed.
- Kidney function and body size shift individual clearance modestly. The curve here is a population estimate, not a lab result.
The part nobody tells you: the drug was a signal, not a repair
GLP-1 drugs work mostly in the brain, quieting appetite circuits, not by changing your metabolism. When the molecule leaves, nothing is broken. Your brain simply returns to its baseline setting, which after major weight loss is tuned hungrier than before. The silence you got used to was borrowed. The good news is that the things that replace it are boring, proven, and entirely in your control: a protein floor, two or three short strength sessions a week, and a smoothed weight trend watched closely enough to catch drift at 4 lbs instead of 20.
That protocol, matched to your washout curve week by week, is exactly what Ellie is built to run.