Pick a compound, set a dose and schedule, and this tool models an estimated relative-level curve using a two-phase absorption/elimination (Bateman) equation — the same superposition principle the in-app Estimated Levels feature uses, extended here with an absorption phase for a more realistic peak. See the full compound list in the Half-Life Data Table.
Level estimator
A one-off estimate — nothing here is saved or sent anywhere.
Absorption half-life defaults to a rough estimate (elimination half-life ÷ 10) since published absorption-rate data is rare for most of these compounds — edit it if you have a better figure.
How to Use This Tool
Five inputs drive the whole model — compound, half-life (auto-filled), dose, frequency and schedule length.
Pick a compoundSelecting one auto-fills a published elimination half-life and shows its evidence tag — how solid that number actually is.
Check (or edit) the half-life fieldsThe elimination half-life comes from the reference library; the absorption half-life is a rough estimate you can adjust if you have a better figure for your specific route of administration.
Enter your dose and frequencyThis models a fixed, repeating schedule — not variable dosing — so pick the frequency you'd actually be using.
Read the chart and statsThe curve shows relative level over your chosen schedule length; peak, trough and steady-state average are calculated from the final dosing cycle, once the curve has stabilized.
How the Model Works
This uses a two-compartment absorption/elimination (Bateman) equation rather than the simpler single-exponential decay used elsewhere on this site, to better reflect that an injected dose doesn't appear in the body instantly — it's absorbed over time, then eliminated.
The Bateman equation. For a single dose, relative level at time t is: Level(t) = Dose × [ka / (ka − ke)] × (e^(−ke·t) − e^(−ka·t)), where ke is the elimination rate constant (ln 2 ÷ elimination half-life) and ka is the absorption rate constant (ln 2 ÷ absorption half-life). This produces a curve that rises to a peak as the dose absorbs, then falls as it's eliminated — rather than jumping instantly to a peak. Standard one-compartment pharmacokinetic model with first-order absorption and elimination, described in pharmacokinetics textbooks (e.g. Rowland & Tozer, Clinical Pharmacokinetics and Pharmacodynamics).
Multiple doses (superposition). For a repeating schedule, the total estimated level at any time is the sum of the still-active contribution from every dose given up to that point — the same superposition principle the in-app Estimated Levels feature uses with its simpler single-exponential model. Linear pharmacokinetics superposition principle — standard for repeated first-order dosing.
Where half-life numbers come from. Elimination half-life figures are pulled from FDA labels where a compound is approved, published clinical-trial data for investigational compounds, or peer-reviewed PK studies — see the evidence tag next to each compound, and the full Half-Life Data Table for sourcing on every entry. See Half-Life Data Table for compound-by-compound sourcing.
Why the absorption half-life is a rough default. Published absorption-rate (ka) data is rare for most peptides — far rarer than elimination half-life data. The default here (elimination half-life ÷ 10) is a simplifying assumption, not a cited figure, and mainly affects how sharp the peak looks shortly after each dose rather than the overall trend. Simplifying assumption, disclosed here rather than presented as sourced data.
Units shown. The y-axis is a relative "level" in the same dose units you entered — not an actual blood concentration, since that would require a volume-of-distribution figure this tool doesn't have. It's useful for comparing peak vs. trough vs. steady-state shape, not for reading off a real concentration. No claim of absolute concentration; relative-unit convention matches the in-app Estimated Levels feature.
Estimate only — not medical advice. This is a mathematical estimate built from public reference data and the numbers you enter — it is not a measurement of your actual blood level and cannot account for your individual absorption, metabolism, body composition, kidney or liver function, or interactions with other compounds. Individual variation can be substantial. This tool is not a substitute for actual blood testing and is not medical advice. See the full methodology page for more detail.
Frequently Asked Questions
What is the Bateman equation?
It's a standard pharmacokinetic formula that models a dose as being absorbed into the body over time (at a rate governed by an absorption half-life) and then eliminated over time (at a rate governed by an elimination half-life). It produces a curve that rises to a peak and then falls, which is more realistic for an injected dose than assuming the peak happens instantly.
Why does this tool use a different model than the in-app Estimated Levels feature?
The in-app feature uses a simpler single-exponential decay model for a lightweight daily-tracking view. This standalone visualizer adds an absorption phase (the Bateman equation) for a more detailed, textbook-style curve — both use the same superposition principle for multiple doses and the same underlying half-life reference data.
Where does the absorption half-life number come from?
For most compounds, we don't have a published absorption-rate figure, so this tool defaults to roughly one-tenth of the elimination half-life as a simplifying placeholder — clearly labeled as such. If you have a better absorption-rate figure for your specific compound and route, edit that field directly.
Is the y-axis a real blood concentration?
No. It's a relative level in the same units as your entered dose, useful for comparing the shape of peaks, troughs, and steady-state across different schedules — not a substitute for an actual lab test of your blood concentration.
What does "steady-state" mean on this chart?
With repeated dosing, levels build up over the first several half-lives until each new dose's contribution roughly balances what's eliminated between doses — that plateau is "steady-state." This tool estimates it from the final dosing cycle in your selected schedule length, so a longer schedule gives a more settled steady-state read.
Why does my chart look almost flat for a fast-clearing compound?
If a compound's elimination half-life is much shorter than your dosing interval (e.g. a 2-hour half-life dosed once daily), the level returns close to zero between doses — the chart correctly shows sharp spikes rather than a sustained curve. That's expected behavior, not a bug.
Can I compare two compounds at once?
Not on this page — it models one compound and one schedule at a time. Open two browser tabs to compare compounds side by side, or use the Half-Life Data Table to compare raw half-life figures directly.
How accurate is this for a blend, like a CJC-1295/Ipamorelin combination?
This tool models a single half-life value per run. A blend contains multiple compounds with different clearance rates, so you'd need to run this tool once per component to see each one's individual curve — combining them into one number (as some reference entries do) loses that distinction.
Does this tool save my inputs anywhere?
No — everything runs locally in your browser and nothing is stored or transmitted. To track your actual dose history and see this same style of estimate built from your real logged doses, see the full Peptide Plug app.
Why should I trust the half-life number this tool defaults to?
Check the evidence tag shown next to your selected compound — it ranges from "FDA label" (highest confidence) down to "Not characterized in humans" (essentially a rough approximation). The Half-Life Data Table shows the sourcing reasoning for every compound in one place.
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