Peptide half-lives run from about 11 minutes (tesamorelin) to about a week (semaglutide). This chart puts every commonly discussed peptide in one place, and tells you what the number is based on: a human study, an animal study, or nothing at all.
Most half-life pages answer for one compound at a time, and most of them present an animal figure and a human figure with equal confidence. This page separates them, because the difference decides whether the number is worth planning anything around. If you want the wider picture first, the guide to peptides, HGH and HCG covers what those three categories actually are.
In This Guide
- The peptide half-life chart
- Read the evidence column first
- Why a 30-minute half-life can have effects that last for days
- How long until a peptide reaches steady state
- What the half-life does not tell you
- Does the route of administration change it?
- Five half-life claims that get repeated and do not hold up
- FAQ
The peptide half-life chart
Half-life here means terminal elimination half-life: the time it takes for the concentration in blood to fall by half. Where a compound has no published human figure, the row says so rather than borrowing a number from a rat study.
| Compound | Half-life | Evidence | Source |
|---|---|---|---|
| Semaglutide | About 1 week | Human, approved product label | FDA Ozempic label |
| Tirzepatide | About 5 days | Human, approved product label | Lilly prescribing information |
| Retatrutide | About 6 days | Human, phase 2 trial | Jastreboff 2023, NEJM |
| CJC-1295 with DAC | 5.8 to 8.1 days | Human study | Teichman 2006, JCEM |
| PT-141 (bremelanotide) | About 2.7 hours (range 1.9 to 4.0) | Human, approved product label | FDA Vyleesi label |
| Thymosin alpha-1 | About 2 hours | Human pharmacokinetic study | Ancell 2001, Rost 1999 |
| Ipamorelin | About 2 hours | Human, PK and PD modelling | Gobburu 1999 |
| GHRP-6 | About 2.5 hours (distribution phase 7.6 minutes) | Human pharmacokinetic study | Cabrales 2013 |
| Hexarelin | About 55 to 76 minutes | Human studies | Imbimbo 1994, Roumi 2000 |
| Sermorelin | About 11 to 12 minutes | Human product labelling | Sermorelin acetate labelling |
| Tesamorelin | About 11 minutes at the 1.28 mg dose | Human, approved product label | FDA Egrifta label |
| AOD-9604 | About 3 minutes after intravenous dosing | Single metabolism study, subcutaneous data absent | Moré 2014 |
| MK-677 (not a peptide) | 4 to 6 hours measured in animals; effects persist about 24 hours | Animal pharmacokinetics, human effect data | Chapman 1996 |
| BPC-157 | Under 30 minutes | Animal pharmacokinetics only | He 2022, PMC |
| GHK-Cu | Estimated hours; no formal human figure | Limited human data | Pickart 2018 review |
| TB-500 (thymosin beta-4 fragment) | Not established in humans | No human pharmacokinetic data | McGuire 2026 scoping review |
| IGF-1 LR3 | Not established; native IGF-1 is about 6 hours | No human data for the analogue | Grahnén 1993 (native IGF-1) |
| Melanotan II | Not established in humans | No formal human PK study; related compound measured at 0.8 to 1.7 hours | Ugwu 1997 (related peptide) |
Half-lives are the figures reported in the sources listed at the end of this page. They are not dosing instructions, and where a label publishes a figure at one specific dose, the dose is stated.
Read the evidence column first
Three kinds of row sit in that chart, and they are not equivalent.
Approved products and human studies. Semaglutide, tirzepatide, tesamorelin and bremelanotide are approved medicines, so their half-lives come from label pharmacokinetics in humans. CJC-1295, ipamorelin, GHRP-6, hexarelin and thymosin alpha-1 have published human studies. These numbers are solid, and they mean what they say: the drug leaves the blood at that rate.
Animal pharmacokinetics. BPC-157 is the important example. The figure under 30 minutes comes from rodent and dog studies, and there is no published human pharmacokinetic study of BPC-157 at all. That does not make the compound inert, for reasons in the next section, but it does mean nobody knows the human half-life, whatever a forum post claims.
No published figure. TB-500, IGF-1 LR3 and melanotan II have no human pharmacokinetic data, and AOD-9604 has one metabolism study with intravenous dosing. On the pages that cover these compounds, the numbers you see are frequently estimates that have been copied between sites until they look established. Marking that difference is the entire reason this chart exists in this format.
Why a 30-minute half-life can have effects that last for days
The most common mistake with half-lives is treating them as a measure of how long something works. They are not. Half-life describes how quickly the compound leaves the bloodstream, and that is only part of the story.
BPC-157 again: cleared in under 30 minutes in animal studies, yet the same body of research reports effects that outlast the exposure by a wide margin. That gap between how long a drug is present and how long its effects persist is called a pharmacokinetic and pharmacodynamic disconnect, and it is common in peptides. The mechanism is usually one or more of these:
- Downstream signalling. The peptide triggers a cascade that keeps running after the peptide is gone, so nitric oxide, growth factor or gene expression changes persist on their own schedule.
- Receptor binding that lasts longer than the plasma curve. A compound can leave the blood quickly while remaining bound at the receptor.
- Tissue distribution. Blood concentration is not the same as concentration at the tissue where the effect happens.
This is why “the half-life is two hours, so it must be useless” and “the half-life is two hours, so inject it eight times a day” are both wrong. The half-life sets the shape of the blood curve. It does not set the length of the effect.
How long until a peptide reaches steady state
Half-life matters more when a compound is taken repeatedly, because it decides how long accumulation takes. As a rule of thumb, four to five half-lives are needed before blood levels stabilise. That is the number to use when people ask how long a peptide takes to build up.
| Compound | Half-life | Approximate time to steady state |
|---|---|---|
| Semaglutide | About 1 week | 4 to 5 weeks |
| Retatrutide | About 6 days | 4 weeks |
| CJC-1295 with DAC | 5.8 to 8.1 days | 4 to 6 weeks |
| Tirzepatide | About 5 days | 3 to 4 weeks |
| Ipamorelin, GHRP-6, hexarelin | 1 to 2.5 hours | Under a day, so accumulation is not a real concern |
The pattern is worth remembering: the long-acting compounds are the ones where a missed dose or a changed dose takes weeks to settle, and the short-acting ones clear before the next dose anyway.
What the half-life does not tell you
- How much reaches the blood. Half-life measures elimination, not absorption. A peptide with a long half-life that is poorly absorbed can still produce low exposure.
- How effective it is. Two compounds with identical half-lives can differ enormously in potency.
- How long the effect lasts. See the disconnect section above.
- Where it goes. Distribution into tissue, and whether it crosses into the compartments that matter for the effect, is a separate question.
- The right dosing interval. That is a clinical decision that depends on the effect curve, not just the elimination curve, and it belongs with a qualified clinician.
Does the route of administration change it?
Yes, and usually it changes absorption rather than elimination. A half-life measured after intravenous dosing tells you about clearance; the same compound given subcutaneously will show a later peak and a lower maximum, because uptake from the tissue is slower. That is why some labels publish different figures for different doses and routes, and why half-lives quoted from an intravenous study cannot be pasted onto a subcutaneous protocol.
| Route | What it changes | Practical consequence |
|---|---|---|
| Intravenous | No absorption step | Figures from these studies describe elimination only, and are the cleanest measures of clearance |
| Subcutaneous | Slower, more variable absorption | Later peak, and the effect can outlast the plasma curve for the reason above |
| Intramuscular | Faster absorption than subcutaneous for most compounds | Earlier peak, similar elimination once absorbed |
| Oral | Digestion and first-pass metabolism | Why almost every peptide is injected, and why the few oral exceptions are small molecules rather than peptides |
| Intranasal | Mucosal absorption, bypasses first pass | Relevant for a few compounds; absorption figures are usually much less characterised |
Five half-life claims that get repeated and do not hold up
- “MK-677 has a 24-hour half-life.” The 4 to 6 hour figure was measured in animals, and the reason once-daily dosing works is that growth hormone and IGF-1 effects persist long after the compound has cleared. The widely copied 24-hour number is an effect duration dressed up as a half-life.
- “BPC-157 clears in about two hours.” The published figure is under 30 minutes, and it comes from animals. Both the number and its origin are usually wrong in retellings.
- “IGF-1 LR3 lasts 20 to 30 hours.” No human pharmacokinetic study of the analogue supports that. Native IGF-1 has been measured at roughly 6 hours; the analogue is designed to resist binding proteins, which should extend it, but by how much in humans is not published.
- “Melanotan II has a 33-minute half-life.” There is no formal human pharmacokinetic study of melanotan II. The frequently quoted figure is imported from a related melanocortin peptide.
- “Half-life is how long it works.” The most common error of all, and the one that leads to the worst dosing decisions in both directions.
FAQ
What is the half-life of BPC-157?
Under 30 minutes in animal studies. There is no published human pharmacokinetic study, so any firm human figure you see quoted is an estimate rather than a measurement.
How long do peptides stay in your system?
It depends entirely on the compound. Tesamorelin and sermorelin are cleared in minutes, ipamorelin and GHRP-6 in around two hours, and the long-acting GLP-1 class in days to a week. The chart above gives the figure and the evidence behind it for each one.
Does a short half-life mean a peptide does not work?
No. Half-life describes how fast the compound leaves the blood, not how long its effects last. Several peptides with very short elimination half-lives produce effects that persist long after the compound has cleared, because the signalling they start keeps running.
Why do different websites give different half-life numbers?
Three reasons, in order of how often they occur: a figure from an animal study is presented as a human one, an effect duration is mistaken for a half-life, and an estimate from one site gets copied by others until it looks established. This page labels which of the three applies.
How long until a peptide reaches steady state?
Four to five half-lives. That is under a day for the short-acting compounds and four to six weeks for the long-acting ones such as semaglutide, retatrutide and CJC-1295 with DAC.
Does the route of administration change the half-life?
It changes absorption more than elimination. A figure measured after intravenous dosing describes clearance; the same compound given subcutaneously will peak later and may produce a flatter curve.
Which peptides have the longest half-life?
Among the compounds people actually search for: semaglutide at about a week, CJC-1295 with DAC at 5.8 to 8.1 days, retatrutide at about 6 days, and tirzepatide at about 5 days.
Is there a published half-life for every peptide?
No, and that is the honest answer for a large part of this category. TB-500, IGF-1 LR3 and melanotan II have no human pharmacokinetic data, and BPC-157 has only animal figures. Rows without a source in the chart above are rows where the number does not exist.
The bottom line
Half-life tells you one useful thing: how fast a compound leaves the blood, and therefore how long accumulation takes when you use it repeatedly. It does not tell you how long the effect lasts, how strong the compound is, or what schedule makes sense.
When you see a half-life quoted, check three things before you use it for anything: is it a human figure or an animal one, is it a measured half-life or an effect duration, and does the source actually say what the site says it says. Those three checks separate this chart from most of what is written on the subject.
Last reviewed: October 2026 by Julian Hart. This page is educational and is not medical advice. Dosing, bloodwork and any health condition belong with a qualified clinician. More guides are collected in the peptides section.
Sources
- FDA. Ozempic (semaglutide) prescribing information.
- Lilly. Mounjaro (tirzepatide) prescribing information.
- Jastreboff AM, et al. Triple hormone receptor agonist retatrutide for obesity: a phase 2 trial. NEJM, 2023.
- Teichman SL, et al. Prolonged stimulation of growth hormone and IGF-I secretion by CJC-1295 in healthy adults. JCEM, 2006.
- FDA. Vyleesi (bremelanotide) prescribing information.
- Ancell CD, et al. Thymosin alpha-1. 2001; Rost KL, et al. Pharmacokinetics of thymosin alpha-1 after subcutaneous administration. 1999.
- Gobburu JV, et al. Pharmacokinetic and pharmacodynamic modelling of ipamorelin in healthy volunteers. 1999.
- Cabrales A, et al. Pharmacokinetic study of GHRP-6 in nine healthy male volunteers. 2013.
- Imbimbo BP, et al. Growth hormone releasing activity of hexarelin in humans. 1994; Roumi M, et al. Kinetics and disposition of hexarelin. 2000.
- Sermorelin acetate product labelling, half-life 11 to 12 minutes after intravenous or subcutaneous administration.
- FDA. Egrifta (tesamorelin) prescribing information, 2025.
- Moré MI, et al. Safety and metabolism of AOD9604. 2014.
- Chapman IM, et al. Stimulation of the GH and IGF-I axis by daily oral administration of MK-677 in older adults. 1996.
- He L, et al. Pharmacokinetics, distribution, metabolism and excretion of BPC-157 in rats and dogs. 2022.
- Pickart L, et al. Regenerative and protective actions of the GHK-Cu peptide. 2018.
- McGuire F, et al. Thymosin beta-4 and TB-500 in tissue healing: a scoping review. 2026.
- Grahnén A, et al. Pharmacokinetics of recombinant human insulin-like growth factor I. 1993.
- Ugwu SO, et al. Skin pigmentation and pharmacokinetics of melanotan-I in humans. 1997.
