Methodology & sourcing

Where these numbers come from.

Health figures should say how well established they are. Every half-life on this site carries an evidence tag, every dose ladder is reproduced from published labeling rather than invented, and where something is not known, the entry says so instead of guessing.

The short version

Every half-life figure on this site carries a tag saying how well established it is. Dose steps are reproduced from manufacturers' published labeling and are offered as presets, never as recommendations. Where something is not well characterised in humans, the entry says so rather than quoting a confident number.

The four evidence levels

Every compound in the Half-Life Data Table and the Half-Life Visualizer carries one of these.

FDA label. The figure appears in an approved product's prescribing information. This is the strongest tier — it is a regulator-reviewed number for a specific approved product.
Clinical trial. The figure comes from published human trial data, including compounds still in development that are not approved for any use. A trial figure is real data, but it is not a regulator-reviewed label claim.
PK study. The figure comes from a published pharmacokinetic study rather than a label or a registration trial. Sample sizes are often small and figures vary between studies, so these carry a wider range.
Not characterised. No reliable human pharmacokinetic data was found. The entry says so explicitly instead of quoting a number, and the visualiser flags it. If you see this tag, treat any curve as illustration only.

Where dose steps come from

And, more importantly, what they are not.

They are reproduced from published labeling. The titration ladders shown on the GLP-1 tracker pages and in the titration planner are the manufacturers' own labeled schedules for approved products.
They exist so the tracker can offer presets. Typing a dose step every week is tedious and error-prone. Presets solve that. They do not constitute advice about which step you should be on.
Your prescriber's schedule always takes precedence. If what you have been prescribed differs from a labeled ladder, that is between you and your prescriber, and the tracker records what you actually take.
Compounds without approved labeling have no dose steps here. Where a compound is not approved, we publish half-life data with its evidence tag and no dose ladder at all, because there is no labeled schedule to reproduce.

Two things worth being explicit about

Both come up often enough to state plainly.

Depot injections are release-limited, not elimination-limited. For oil-based esters — testosterone cypionate, estradiol valerate and similar — the long half-life describes how slowly the ester leaves the injection-site depot, not how fast the hormone itself clears. The hormone's own half-life is far shorter. Every affected entry carries a note saying so.
Some formats do not fit a rise-and-fall model at all. A transdermal patch delivers at a near-constant rate while worn. Fitting a curve model to it produces a shape that looks meaningful and is not, so that entry is tagged as limited and says explicitly that the curve is illustrative.

What we will not publish

Deliberate omissions, not gaps.

Dosing recommendations. Nothing on this site tells you what dose to take, when to change one, or whether a compound suits you. Those are clinical decisions and we are not qualified to make them for you.
Vendors or sourcing. We do not sell, supply, source or link to anywhere that does, and we do not take affiliate arrangements from any supplier.
Efficacy or safety claims. We do not tell you what a compound will do for you or how safe it is. We publish clearance figures and arithmetic.
Invented precision. Where the published range is wide, we show the range. A single confident number where the literature disagrees would be more readable and less honest.

Who writes this

Relevant, because health content should say who is behind it.

Peptide Plug is built by Nick Dillon, working alone. I am not a clinician, a pharmacist or a researcher, and nothing here should be read as though I were. What I am is someone who got tired of running complex protocols out of spreadsheets and screenshots, and built the tool I wanted — then found the arithmetic was the part everyone else was getting wrong too.

That background is exactly why this site does arithmetic and record-keeping rather than advice. Reconstitution math, cost per dose and interval counting are things a careful builder can get right and verify. What dose you should take is not, and any site that blurs the line between the two is doing you a disservice. More about the project →

Found an error?

Please tell us — corrections are the most useful message we get.

If a figure here looks wrong, or you have a primary source that contradicts one, get in touch through Instagram or Facebook. Include the compound and the source if you can. Figures get corrected and the evidence tag updated; the data table shows the current state rather than a frozen snapshot.

Reference information, not medical advice. Published pharmacokinetic figures are population averages drawn from specific study populations. Individual clearance varies, sometimes substantially, and no figure on this site predicts what is happening in your body. Only a blood test measures that.

Frequently Asked Questions

Are the dose steps on this site a recommendation?

No. They are the manufacturers' published labeled titration schedules, reproduced so the tracker can offer them as presets rather than making you type a step every week. Your prescriber's schedule takes precedence over any of them.

Why do some compounds show a range instead of a number?

Because the published literature reports a range. Showing a single confident figure where studies disagree would read better and be less honest, so the range stays.

What does “not characterised” mean?

That no reliable human pharmacokinetic data was found for that compound. Rather than quote a number from an unreliable source, the entry says so and the visualiser flags it. Treat any curve for such a compound as illustration only.

Is the estimated level curve a prediction of my blood levels?

No. It is a mathematical model built from a published population figure and the numbers you enter. Individual clearance varies and only a blood test measures your actual levels.

Why is a testosterone or estradiol ester half-life so long?

Because the figure describes release from the injection-site depot rather than the hormone's own clearance, which is much faster. Every affected entry carries a note saying so.

Do you take money from suppliers?

No. We do not sell or supply anything, we do not link to vendors, and we have no affiliate arrangements with any supplier. Revenue comes from Pro subscriptions only.

Who writes the content on this site?

Nick Dillon, who builds Peptide Plug, working alone. He is not a clinician, which is precisely why the site limits itself to arithmetic and record-keeping rather than advice.