GLP-1 plotter tools compared: features, models and limits

A plotter turns a dose schedule into a curve. People use one to see when levels peak, how much carries over from week to week and what a missed or late dose does. The tools below all offer some version of that for retatrutide, tirzepatide or semaglutide, alone or inside a dose-tracking app. We list them alphabetically, describe each with the same fields and do not score or rank them. GLP Ladder’s own multi-compound plotter is one row, described by the same fields as the others.

The tools side by side

Each entry reflects what the tool’s own website or app store listing said when checked on Oct 19, 2026. “Not stated” means we did not find the feature described; it may still exist. Tools change often, so check the tool itself before relying on a feature.

Homepages, for checking details yourself: Glapp, GLP-1 Plotter, GLP-1 Tracker, GLP-3 Wiki, Pep on the App Store, PeptideCalc, Regimen, Retadose and Shotsy. GLP3 Planner is described in the tables but not linked here.

A few notes the tables cannot hold. GLP-1 Plotter (glp1plotter.com) and GLP-1 Tracker (glp1plotter.app) have similar names, but neither site states a connection to the other. GLP-1 Plotter’s changelog shows its last entry in April 2024 and gives retatrutide a 6-day half-life. GLP3 Planner displayed a “site under construction” banner and states that it does not sell medication. The GLP-3 Wiki website’s calculator converts doses to syringe units and does not plot levels; only the app draws a curve. PeptideCalc shows a single-dose decay table rather than a multi-dose schedule.

What a plotter can tell you

A one-compartment plotter treats the body as one well-mixed space. Each dose is absorbed at a steady proportional rate and cleared at a steady proportional rate set by the half-life. That simple model is good at a few things:

• Timing. When the modeled amount peaks after each dose and when it bottoms out before the next.
• Build-up. With weekly doses, some of each dose is still present when the next arrives. The ratio of steady-state amount to a single dose is the accumulation ratio: 1.6101 at a 5-day half-life, 1.8033 at 6 days and 2.0000 at 7 days.
• Time to steady state. About 97% of steady state is reached after 5 half-lives, so about 25 days at 5 days and about 35 days at 7 days. The tirzepatide label says steady state is reached after 4 weeks of weekly dosing (DailyMed, Aug 28, 2026), and the Ozempic label says 4 to 5 weeks (Novo Nordisk, Jun 1, 2026).
• Schedule comparisons. How a different step length, a skipped week or a day change shifts the curve relative to another schedule.

Here is the single-dose arithmetic behind those numbers for semaglutide, using a 7-day half-life:

What a plotter cannot tell you

• Blood concentration. Turning an amount into a concentration needs a volume of distribution and bioavailability. Those vary by person. Published bioavailability under the skin is 80% for tirzepatide (DailyMed, Aug 28, 2026) and 89% for semaglutide (Novo Nordisk, Jun 18, 2026); for retatrutide we found no published figure. GLP Ladder therefore sets bioavailability to 1 and labels its output as a relative amount in milligram-equivalents. Several other tools say the same about their curves.
• Your own half-life. Plotters use population averages. The tirzepatide figure is about 5 days, and section 12.3 of the Zepbound label says 5 to 6 days (DailyMed, Aug 28, 2026). Retatrutide’s comes from one Phase 1b study: approximately 6 days (The Lancet, Oct 27, 2022), with a single-dose study summarized as about 5 to 7 days (Eli Lilly, hosted on ClinicalTrials.gov, Aug 29, 2022). Tools pick different points in those ranges; Retadose, for example, states an assumption of about 144 to 165 hours.
• Effect or side effects. A higher modeled amount does not translate into a predicted weight change, appetite level or nausea risk. No plotter here models outcomes.
• Absorption differences. Most models use one fixed absorption rate. The labels report a range: tirzepatide peaks at a median of 24 hours with a range of 8 to 72 hours (DailyMed, Aug 28, 2026), and semaglutide at 1 to 3 days (Novo Nordisk, Jun 18, 2026).
• Anything about product quality. A plotter assumes the labeled amount of drug in every dose. That assumption fails for products outside the regulated supply chain, including research-use retatrutide.

None of the tools, including ours, gives dosing advice, and none should be used to choose a dose. For approved drugs, talk to your prescriber. Retatrutide is investigational and not approved anywhere, so any retatrutide curve models how trials were run, not approved use.

Model choices that change the curve

Two tools using the same model can still draw different curves if they pick different inputs.

Sources: (DailyMed, Aug 28, 2026) (Novo Nordisk, Jun 18, 2026) (The Lancet, Oct 27, 2022) (Eli Lilly, hosted on ClinicalTrials.gov, Aug 29, 2022)

If two tools disagree, check these inputs first. A tool that uses 7 days for retatrutide will show more build-up than one that uses 6 days, with no difference in the underlying drug. GLP Ladder documents its choices on its model card.

Questions to ask of any tool

• Does it name its model and list the half-life and absorption values it uses?
• Does it label the y-axis as a relative amount or estimate, rather than implying a blood level?
• Can you see the numbers in a table, not just a chart, and export them?
• Where is your data stored: only in the browser or on the phone, or on the company’s servers? Does it require an account?
• Does the page carry advertising, vendor promotions or affiliate links?
• Does it list the compounds you care about, and does it say clearly when one is not approved?

Using GLP Ladder’s plotter

GLP Ladder’s plotter runs its calculations in your browser, and there is no account. The schedule is stored in the page address, so the share link reproduces it exactly; anyone you send that link to can see the schedule. The default data table renders without JavaScript, and CSV and JSON downloads give you the full series. Open the multi-compound plotter to overlay compounds, or go straight to the retatrutide plotter, tirzepatide plotter or semaglutide plotter. The half-life guides for retatrutide, tirzepatide and semaglutide explain where each input comes from, and the compound hubs collect the rest.