GLP-1 Plotter: Tirzepatide & Semaglutide Levels

What a GLP-1 plotter shows

One idea, drawn out: each weekly injection lands before the last one has cleared, so the leftovers stack. Pick a medication and a number of weeks, and the tool adds up the decay curve of every dose given so far, normalised so a single first dose peaks at 1. The result is a rising sawtooth — a peak after each shot, a trough just before the next — that climbs steeply for the first few weeks and then stops climbing.

It stops because clearance catches up. Once the amount your body removes over seven days equals the amount you inject, the peaks stop getting higher. That flat ceiling is steady state, and everything useful about this page follows from when it arrives.

The arithmetic behind the plateau

How high the plateau sits depends on one thing: how much of each dose is still there when the next one goes in. That fraction is 0.5 raised to the power of 7 divided by the half-life in days. Plug in the half-lives the tool uses and the whole curve falls out.

The longer half-life is why semaglutide stacks higher and takes a week longer to settle. Those plateau multiples are this model's own arithmetic, not figures printed in any drug label — read the shape, not the decimal. What the labels do report is the timing, and it matches: steady state at 4 weeks of once-weekly tirzepatide, and 4–5 weeks for semaglutide.

How many weeks until you are actually on the top dose

Every plotter draws the curve for a dose you have already chosen. Almost none of them answers the question underneath it: so when do I get there? The labels do, and the answer is a calendar.

The Wegovy label prints those week numbers directly in its escalation table. For Zepbound and Ozempic the weeks are the label's own minimum intervals added up. Either way these are floors, not schedules — a prescriber can hold you longer at any step, and many do, particularly where side effects or supply intervene. Wegovy's 7.2 mg step sits above the table: it is permitted only after at least 4 weeks tolerating 2.4 mg, so week 21 at the very earliest.

The tirzepatide row is also why vial strength keeps changing on the way up — Zepbound vial sizes covers what each rung is dispensed as. To put real dates against the rungs, map the titration ladder onto real dates.

Why two GLP-1 plotters draw different curves

Run the same query and you will get visibly different curves for the same drug from different tools. Here is the reason nobody discloses: the tirzepatide half-life is a range on the label — approximately 5 to 6 days on the US Zepbound label, about 5 days on the UK Mounjaro SmPC — and which end you pick changes the answer.

At 5 days, 38% of a dose is still present when the next is due and the plateau settles near 1.6× a single dose. At 6 days it is 45% and about 1.8×. Same drug, same arithmetic, a 12% difference in the ceiling purely from which label number the tool picked up. This one uses 5 days — which is why the shape, not the decimal, is the readable part. If a plotter will not tell you its half-life input and where it came from, it is asking you to trust an unlabelled axis; the Sources block below is this tool's answer to that. For the doses themselves rather than the curve, see the GLP-1 dose conversion chart.

Why every step of the ladder waits four weeks

This is the thing the curve explains better than any paragraph. Tirzepatide climbs from 2.5 mg to 15 mg in 2.5 mg steps, with at least four weeks at each step. Ozempic runs 0.25 mg to a 2 mg maximum. Wegovy runs 0.25 mg to 2.4 mg, with a further 7.2 mg step permitted since 2026 and 1.7 mg allowed as a maintenance dose. In every case the hold is about as long as it takes to reach the new steady state.

So a verdict formed in week one or two of a new dose is a verdict on a level you have not settled at yet — you are still on the climbing part of the curve, and the peaks are still rising underneath you. It is also why the first fortnight after a step-up is the roughest part: when Zepbound side effects peak tracks that window, and what to expect when you increase your Ozempic dose does the same for semaglutide. Sitting out the full interval is what turns "how do I feel on this dose" into a question with a real answer. Dose changes are your prescriber's call; the plot only explains why the interval exists.

The trap: reading it as a blood level

The vertical axis is relative and has no units. There is no mg/L on it, and nothing in the model knows your weight, your kidney function, your injection site, or the milligrams you are actually on. Two consequences. Your curve is not comparable with anyone else's. And the plot holds one dose constant for the whole window: a step up simply lifts the whole curve to a proportionally higher plateau and restarts the same 4–5 week climb, which is why the top-dose table above tells you more than an animated step would.

A related misreading: a bigger dose does not take longer to reach steady state. Time to plateau is set by the half-life alone. Double the dose and the plateau doubles; it still arrives in the same four to five weeks.

Stopping is not instant either

Run the same arithmetic backwards and the tail is long. Semaglutide is still present in the circulation about 5 weeks after a last dose on the Ozempic label, and the Wegovy label puts it at about 5–7 weeks. Tirzepatide clears faster — a half-life of roughly 5 to 6 days on the Zepbound label, about 5 days on the Mounjaro and UK labels — but is still measurable for weeks. That is why appetite does not come back the morning after a missed shot, and why a side effect that started this week may belong to a level built up over the last month.

Like the plateau table, those figures are this model's own arithmetic on the label half-lives — 0.5 raised to days ÷ half-life — not numbers printed in any label. But they check out against one: five weeks is five halvings of a roughly week-long half-life, leaving about 3% of a dose, which is the arithmetic behind the Ozempic label's own statement that semaglutide is present in the circulation for about 5 weeks after the last dose. For a shot that is merely late rather than stopped, see what the labels say when you miss a dose; for a planned exit, weaning off semaglutide.

Where this tool does not apply

It models once-weekly injection only. Daily oral dosing has a different shape entirely and this curve says nothing about it, and splitting a weekly dose across the week changes the sawtooth rather than the plateau — splitting a weekly GLP-1 dose goes through what that actually does. Retatrutide is investigational and not approved anywhere; the ~6-day half-life is a reported figure with no approved label behind it, so treat that line as illustrative only. And the model has no absorption phase — it places each peak at the instant of injection, whereas a real peak arrives some time after the shot. It is a teaching diagram for the shape of accumulation, not a pharmacokinetic prediction for you.