Tools/Half-life calculator
Peptide half-life
calculator
Pick a compound with a published half-life, or enter your own, and see how long it persists after a single dose, how much it accumulates when dosing is repeated at a given interval, and when the body reaches steady state. Every result is a multiple of one dose. This is an educational model of first-order elimination — it is not dosing guidance and does not recommend a compound, amount or interval.
Half-life 1 h. Human intravenous and subcutaneous studies, on the order of an hour.
Time between repeat doses. Change it to see how the interval, not the amount, sets accumulation.
One dose shows single-dose washout; more doses show accumulation towards steady state.
Accumulation ratio at steady state
1× one dose
24 half-lives per interval · t½ 1 h · every 24 h
No meaningful accumulation: each dose is essentially gone before the next.
Steady-state peak
1× one dose
Steady-state trough
0× one dose
~90% of steady state
3.3 h
~97% of steady state
5.1 h
Single-dose elimination milestones
| Cleared | Half-lives | Time after dose |
|---|---|---|
| 50% | 1 | 1 h |
| 75% | 2 | 2 h |
| 90% | 3.3 | 3.3 h |
| 97% | 5 | 5.1 h |
Every figure is a multiple of one dose, whatever that dose is. The tool never reports a concentration and never suggests an amount or an interval.
Relative amount in the body over time
8 doses every 24 h
Model: one-compartment, first-order elimination, instantaneous absorption. Real subcutaneous peptides absorb over hours and the curve is smoother; the accumulation arithmetic is unchanged.
Step 01
Half-life to rate
k = ln 2 ÷ t½. A 7-day half-life gives k ≈ 0.0041 per hour, and the fraction of a dose still present after t hours is e^(−kt). Half is gone after one half-life, 97% after five.
Step 02
Accumulation ratio
R = 1 ÷ (1 − e^(−kτ)), where τ is the interval between doses. Dosing every half-life gives R = 2; dosing every five half-lives gives R ≈ 1.03 — essentially no carry-over.
Step 03
Steady state
The approach to steady state is 1 − e^(−kt): 90% after 3.3 half-lives, 97% after 5. It depends on the half-life alone, not on how often or how much is given.
Half-lives on file
Every compound the calculator knows, with the figure its profile quotes and where that figure comes from. Compounds with no published pharmacokinetic data are deliberately absent.
| Compound | Half-life | Published range | Basis |
|---|---|---|---|
| Tesofensine | 9.2 days | — | Human oral pharmacokinetics; the active metabolite NS2360 persists longer |
| CJC-1295 with DACCJC-1295 profile | 7 days | 5.8 days – 8.1 days | Human subcutaneous pharmacokinetics, 5.8–8.1 days |
| Semaglutide | 6.9 days | — | Human subcutaneous pharmacokinetics (product monograph), about 7 days |
| Retatrutide | 6 days | — | Phase 1 subcutaneous pharmacokinetics, about 6 days |
| Tirzepatide | 4.9 days | — | Human subcutaneous pharmacokinetics (product monograph), about 5 days |
| hCGHCG profile | 30 h | 24 h – 36 h | Terminal half-life after injection in humans |
| PT-141 (bremelanotide)PT-141 profile | 2.7 h | 1.9 h – 4 h | Human subcutaneous pharmacokinetics (approved-product labelling) |
| Ipamorelin | 2 h | — | Human intravenous pharmacokinetic modelling |
| Thymosin alpha-1Thymosin Alpha-1 profile | 2 h | — | Human plasma after subcutaneous injection |
| GHRP-2 | 1 h | — | Human intravenous and subcutaneous studies, on the order of an hour |
| Melanotan II | 1 h | — | Early human pharmacokinetics, on the order of an hour |
| GHRP-6 | 30 min | 15 min – 1 h | Human intravenous pharmacokinetics, 15–60 minutes |
| CJC-1295 without DAC (Mod GRF 1-29)CJC-1295 profile | 30 min | — | Human pharmacokinetics of GRF(1-29) analogues, roughly 30 minutes |
| BPC-157 | 30 min | — | Rodent and dog plasma pharmacokinetics, under 30 minutes; no human data |
| Kisspeptin-54Kisspeptin profile | 28 min | — | Human intravenous pharmacokinetics, about 28 minutes |
| Tesamorelin | 26 min | 26 min – 38 min | Product monograph: 26 minutes in healthy adults, 38 minutes in HIV-infected patients |
| DSIP | 15 min | — | Human plasma, minutes to roughly a quarter of an hour |
| Glutathione | 12 min | 10 min – 15 min | Human intravenous pharmacokinetics, 10–15 minutes in plasma |
| Kisspeptin-10Kisspeptin profile | 4 min | — | Human intravenous pharmacokinetics, about 4 minutes |
Frequently asked questions
What is a peptide's half-life?
The elimination half-life is the time it takes for the amount of a compound in the body to fall by half once absorption is complete. It is a property of how the body clears the molecule — kidney filtration, enzymatic breakdown, binding to albumin — rather than of the dose. Each half-life removes half of what remains, so the decline is exponential, not linear.
How many half-lives until a peptide is gone?
After one half-life 50% remains; after two, 25%; after three, 12.5%; after five, about 3%. Pharmacology texts treat four to five half-lives as effectively cleared, because the remainder is below what most assays detect. A compound with a 7-day half-life therefore takes roughly five weeks to wash out, while one with a 30-minute half-life is essentially gone within a few hours.
What is steady state?
Under repeat dosing at a fixed interval, the amount eliminated between doses eventually equals the amount each dose adds. From that point the peak and trough repeat identically every interval — the body is at steady state. Reaching it depends only on the half-life: about 90% of the way there after 3.3 half-lives and about 97% after 5, regardless of how often the compound is given.
What is the accumulation ratio?
The accumulation ratio is the steady-state peak divided by the amount a single dose contributes. It is calculated as 1 ÷ (1 − e^(−kτ)), where k is the elimination rate constant (ln 2 ÷ half-life) and τ is the dosing interval. A ratio near 1 means each dose is essentially gone before the next; a ratio of 3 means the body carries three doses' worth at the peak once dosing has settled.
Why do weekly compounds like semaglutide build up?
Semaglutide's published half-life is about 7 days, and the studies that established it used a once-weekly interval — roughly one half-life. Half of each dose is still present when the next arrives, so the amount in the body roughly doubles at steady state and takes four to five weeks to get there. That is why trials of these compounds report a gradual build rather than an immediate plateau, and why the effect of a change persists for weeks.
Does a short half-life mean a short duration of effect?
No. Half-life describes how long the molecule circulates, not how long its effects last. BPC-157 is the standard example: rodent and dog data put its plasma half-life under 30 minutes, yet the animal studies dose it once daily and report effects on tissue that outlast the compound by days. Signalling cascades, receptor occupancy and tissue-level changes can persist long after the peptide itself is gone.
Why are some compounds missing from the list?
The calculator only lists compounds whose profile quotes a published half-life. Many research peptides — TB-500, GHK-Cu, Epithalon, MOTS-c, Semax and Selank among them — have no human pharmacokinetic study, or only fragmentary animal data. Rather than guess, those compounds are left off; use the custom half-life option if you have a figure from the literature you want to explore.
Is this medical advice?
No. The calculator applies textbook first-order elimination arithmetic to a published half-life. It does not recommend a compound, a dose or an interval, and it does not model absorption, distribution or effect. Canada Peptides compounds are sold for research use only.
Related tools and reading
Next step
Read the compound profiles
Each profile quotes the half-life used here alongside the study it comes from, the compound's mechanism, and the terms — half-life, titration, bioavailability — that explain the numbers.
Disclaimer
This calculator applies first-order elimination arithmetic to published half-lives. It does not recommend compounds, doses, intervals or protocols, and it does not model absorption, distribution or effect. Canada Peptides compounds are sold for research use only, and nothing on this page is medical advice. Consult a licensed physician before using any peptide compound in any context outside controlled research.