The calculation workspace
Peptide Half-Life Visualizer
Model how repeated doses accumulate toward steady state, or how a single dose clears.
Enter a dose, a dosing interval, and a half-life. The tool plots the modeled amount over time, adding each dose to whatever is left of the previous ones, and reports the peak and trough of every cycle. Single Dose Decay instead follows one dose down: how much is left after a given time, how long it takes to fall to a level you choose, and when 50 to 99 percent has cleared. This is a mathematical model for reference and tracking, not a dosing recommendation.
1. Model the Curve
| Milestone | Amount left | Time after dose | Half-lives |
|---|
| Dose | Time | Peak after dose | Trough before next | % of steady state |
|---|
2. The Math
A single dose decays exponentially. After a time t has elapsed, the modeled amount remaining from a dose of size D with half-life T is:
With repeated dosing, every dose you have already taken is still decaying, so the total at any moment is the sum of the leftovers of all prior doses plus whatever was just administered. That sum is what this tool plots. The full worked example, including a step-by-step table, is in the peptide half-life tracking guide.
Keep the units consistent. Mixing hours and days in the same formula is the most common error in this calculation. The tool converts both inputs to hours internally, so you can set each dropdown independently.
3. Reading the Result
- Peak is the modeled amount immediately after a dose is taken.
- Trough is the modeled amount just before the next dose is due. This is the number that tells you how much is carrying over.
- Steady state is where peaks and troughs stop climbing. It arrives after roughly four to five half-lives regardless of the dose size.
- The percentage column compares each cycle's peak against the theoretical steady-state peak, so you can see how close the curve has settled.
- In Single Dose Decay, the clearance timeline lists when 50, 75, 90, 95, and 99 percent of one dose is modeled to be gone. Those points always fall at the same number of half-lives: 1, 2, about 3.3, about 4.3, and about 6.6.
When the dosing interval is much longer than the half-life, almost nothing carries over and the curve returns near zero between doses. When the interval is shorter than or close to the half-life, the leftovers stack and the curve climbs for several cycles before flattening.
4. What This Tool Does and Does Not Do
- It applies one-compartment exponential decay to the numbers you enter.
- It does not know your absorption, metabolism, body composition, kidney or liver function, or any other individual factor.
- It assumes every dose is identical, on time, and fully absorbed. Real dosing is not.
- It does not choose a dose, an interval, or a schedule, and it is not a substitute for a prescriber.
- Half-life values are population reference figures. Published ranges vary, and individual values vary more.
5. FAQ
What does this half-life visualizer show?
It models what happens when a dose is repeated on a fixed interval. Each dose decays exponentially according to the half-life you enter, and the tool adds the leftovers together to show how the modeled amount builds up over time toward a steady state.
What is steady state?
Steady state is the point where the amount cleared between doses roughly equals the amount each new dose adds, so the peaks and troughs stop rising. As a rule of thumb it takes about four to five half-lives to get close.
Why does a long half-life cause accumulation?
If the dosing interval is shorter than or similar to the half-life, a meaningful fraction of each dose is still present when the next one arrives. Semaglutide is the common example: an elimination half-life of roughly 165 hours against a once-weekly interval of 168 hours means about half of each dose remains when the next is due. See the half-life tracking guide.
How long does a single dose take to clear?
Switch to Single Dose Decay. Each half-life removes half of what is left, so about 50 percent is cleared after one half-life, 75 percent after two, 90 percent after about 3.3, 95 percent after about 4.3, and 99 percent after about 6.6. The tool converts those milestones into hours or days for the half-life you enter, and can also tell you how much is left after a given time or how long it takes to fall to a level you choose.
Does this tool tell me what dose to take?
No. It is a model built from numbers you type in. It does not know your body, your prescription, or your clinical situation, and it does not recommend a dose or a schedule. Dosing decisions belong to your prescriber.
Where do the half-life presets come from?
Only compounds with a citable published value are offered as a preset, and each preset displays its source when selected. Everything else is entered by hand, which keeps the tool from implying a reference value that does not exist.