Peptide half-life calculator
Choose a compound, a dose, and a dosing interval. The chart shows how the estimated amount in your system builds across repeated doses, where it levels off, and how long it takes to clear.
Estimates for education — not a clinical measurement.
This model uses published population half-lives and simple one-compartment maths. It is not a plasma concentration, it does not know your body, and it is not dosing advice. Confirm anything that matters with your prescriber or pharmacist.
Your schedule
Half-life: 6.9 d · Time to peak: 24 h
FDA prescribing information for Ozempic/Wegovy: terminal half-life ≈ 1 week (~165 h); Tmax 1–3 days after subcutaneous dosing.
Estimated amount in system
Relative active amount from your dose, summed across repeated doses. The dashed line is the steady-state average.
- Steady-state peak
- 1.81 mg
- Steady-state trough
- 1 mg
- Accumulation factor
- 1.98×
- Time to steady state
- 34.4 d
- Time to clear
- 34.4 d
- Peak to trough drop
- 45%
Estimates only. Values are relative amounts, not plasma concentrations.
How the calculation works
A half-life is the time it takes for half of what is in your system to be eliminated. After one half-life about 50% remains, after two about 25%, after three about 12.5%. The decline is exponential, which is why a compound never quite reaches zero — it just becomes negligible.
When you dose again before the previous dose has cleared, the leftovers stack. The model adds each dose's remaining amount together, which is what the shaded area on the chart shows. Where a time-to-peak is known, an absorption phase is included too, so the curve rises to a peak instead of jumping instantly.
Accumulation and steady state
The accumulation factor is 1 / (1 − e^(−ke·τ)): the ratio between the level at steady state and the level after a single dose, where τ is your interval. Dosing at intervals shorter than the half-life produces more accumulation; dosing far apart produces almost none. Levels stop climbing at roughly five half-lives — that is steady state, where the amount going in each interval matches the amount cleared.
How long a compound takes to clear
The five-half-life rule works in reverse too: about five half-lives after the last dose, roughly 97% has been eliminated. For a compound with a one-week half-life that is over a month; for one with a two-hour half-life it is most of a day.
What this tool does not do
It does not recommend a dose, an interval, or a compound. It does not model your kidney or liver function, body weight, injection site, or product quality. Half-life values are population estimates from published literature and vary between people.
Related tools: peptide dose calculator, reconstitution calculator, and the full free tool index.
FAQ
- How long does it take to reach steady state?
- About five half-lives of repeated dosing on the same schedule. For a compound with a half-life near one week, that is roughly four to five weeks.
- What does the accumulation factor mean?
- It is how many times higher the level sits at steady state compared with a single dose on the same schedule. A factor of 2 means the level plateaus at about twice the single-dose peak.
- Is this the same as a blood concentration?
- No. The chart shows a relative amount-in-system estimate scaled to the dose you enter, not a measured plasma concentration. Only bloodwork measures that.
- My compound isn't in the list. Can I still use this?
- Yes. Choose "Custom half-life" and enter the value in hours from your own source. The maths is identical — the compound list is only a convenience so you do not have to look the number up.
Half-life values are literature estimates used for educational modelling and are reviewed periodically. Nothing here is medical advice.