- STACK
- Free tools
- Level simulator
Level simulator: how a half-life shapes the curve
Pick a reference compound or type a half-life, choose a schedule, and watch the estimated level build toward a steady state. It is the same first-order decay model the STACK app draws from your logged doses — shown here as an illustration, not a measurement.
Estimated level
once a day, half-life 24 h, for 4 weeks · 28 doses
Estimate only. Modelled from the published half-life you selected and the doses you logged — not a measured blood level. Do not use it to make medication decisions.
What the curve is
A single dose is modelled as decaying by half every half-life. Repeated doses add up: each new dose lands on top of what is left from the earlier ones. The curve is the sum, sampled hour by hour and scaled to the steady-state peak, which is why the y-axis reads in percent and not in any unit of concentration.
The half-life fully determines how much accumulates. Dosed more often than one half-life, the level stacks well above a single dose; dosed less often, it almost clears between doses. Reaching 90% of steady state takes about 3.3 half-lives; 97% takes about 5, whatever the compound.
What it is not
- Not a blood level. Real pharmacokinetics involve absorption, distribution and individual variation that a one-compartment sketch ignores.
- Not a target. There are no ranges, thresholds or alerts here, and none in the STACK app.
- Not dosing guidance. The schedule you pick is an input to the drawing, not a suggestion.
Published half-lives in the reference set
Each value below links to the compound page with its source. Compounds without a published human value are listed on the compounds index with that stated plainly.
| Compound | Class | Reference half-life |
|---|---|---|
| Tirzepatide | GLP-1/GIP | 120 h (5 days) |
| Semaglutide | GLP-1 | 168 h (7 days) |
| Retatrutide | GLP-1/GIP/GCG | 144 h (6 days) |
| CJC-1295 with DAC | peptide | 167 h (7 days) |
| Ipamorelin | peptide | 2 h |
| Liraglutide | GLP-1 | 13 h |
| Cagrilintide | amylin analogue | 177 h (7.4 days) |
| Sermorelin | GHRH analogue | 6.6 min |
| Tesamorelin | GHRH analogue | 30 min |
| PT-141 (bremelanotide) | melanocortin agonist | 2.7 h |
| Thymosin alpha-1 | thymic peptide | 2 h |
| Kisspeptin-10 | KISS1R agonist | 3.8 min |
| Glutathione | tripeptide antioxidant | 14.1 min |
In the app, the curve is drawn from your log
STACK builds this curve from the doses you actually logged, at the times you logged them, with the half-life you set for each compound. Today shows a compact 7-day view; Pro adds 30-day, 90-day and all-time ranges and overlays.
Estimate only. Modelled from the published half-life you selected and the doses you logged — not a measured blood level. Do not use it to make medication decisions.