The half-lives of the peptides in our range run from a few minutes to eight days. Ipamorelin clears from the blood within two hours, CJC-1295 with DAC needs close to a week, and for MOTS-c and BPC-157 nobody has measured it in humans. Below are the figures from published studies, the source of each one, and why the effect can last longer than the molecule stays in the blood.
What half-life means
Half-life is the time after which the concentration of a substance in the blood falls by half. After two half-lives a quarter is left, after three an eighth. The figure describes the molecule itself, not its effect in the body.
The distinction matters with peptides that release growth hormone. A molecule can clear from the blood in an hour while raised IGF-1 lasts for many days. That is why the table below has a second column next to half-life, with the duration of the measured effect.
Figures from human studies
| Compound | Half-life | How long the effect lasted |
|---|---|---|
| Ipamorelin | 2 hours | a single growth hormone release peaking after 40 minutes |
| CJC-1295 with DAC | 5.8 to 8.1 days | growth hormone raised for over 6 days, IGF-1 for 9 to 11 days |
| Semaglutide | 145 to 168 hours | peak concentration 30 to 36 hours after injection |
| Tirzepatide | about 5 days | once-weekly dosing keeps a steady concentration |
| Retatrutide | about 6 days | once-weekly dosing keeps a steady concentration |
| GHK-Cu | under 30 minutes | no measured duration of effect after systemic administration |
| MGF | minutes | no completed human study |
Where the figures come from
Ipamorelin was measured in a study published in Pharmaceutical Research in 1999. Eight healthy men at each of five dose levels received a fifteen-minute infusion. The terminal half-life was 2 hours, clearance 0.078 litres per hour per kilogram, and the volume of distribution 0.22 litres per kilogram. Growth hormone was released once, peaking after 0.67 hours and then declining exponentially.
CJC-1295 was studied in 2006 in the Journal of Clinical Endocrinology and Metabolism, in healthy adults aged 21 to 61. After a single subcutaneous injection growth hormone rose 2 to 10 times for more than six days, and IGF-1 rose 1.5 to 3 times for 9 to 11 days. After multiple doses IGF-1 stayed above baseline for up to 28 days. These figures apply to the version with DAC technology and must not be carried over to the version without it, as the guide to CJC-1295 with and without DAC explains.
Semaglutide has a pharmacokinetic review published in 2024 that gathered 17 studies. The half-life after subcutaneous administration fell between 145 and 168 hours, roughly a week. Tirzepatide was described by a population model built from 19 studies, with a half-life of about 5 days. Retatrutide has a mean half-life of about 6 days in a 2024 review. The three molecules are compared in the guide to semaglutide, tirzepatide and retatrutide.
HCG: the route changes the curve, not the result
With chorionic gonadotropin something more interesting than half-life alone was measured. In a study in Fertility and Sterility from 1991, twenty-four healthy men received 5000 units, one group subcutaneously, the other intramuscularly. After subcutaneous administration the peak concentration came later and the half-life was longer.
The response of testosterone, LH and FSH was identical in both groups. The authors therefore considered the subcutaneous route as effective as the intramuscular one. The substance itself is described on the HCG page.
Peptides nobody has measured
For a good part of the catalogue the answer is: not known. No human pharmacokinetic studies have been published for BPC-157, TB-500, MOTS-c or SLU-PP-332, so we give no figure here. The data come only from animals and cell cultures, and converting them to humans would be guesswork.
MGF is a separate case. The natural molecule clears from the blood within minutes, and that is exactly the problem the pegylated version was meant to solve. The difference is explained in the guide to MGF and PEG-MGF.
Why this is not a protocol of use
Half-life does not tell you how often to give anything, and we draw no such conclusions. The studies above were run in clinical centres, on small groups, with intravenous or subcutaneous administration under supervision. Everything in our range is sold as material for laboratory research, as the guide to the legal status of peptides explains.
The number that matters more when buying is the shelf life of the vial, not of the blood. A dissolved peptide keeps in the fridge for a limited time, and that is covered in the guide to storing powder and solution. Prices for every item are on the price list.
Frequently asked questions
Which peptide in the range has the longest half-life?
CJC-1295 with DAC, at 5.8 to 8.1 days. Close behind are retatrutide and tirzepatide, at about six and five days.
Does a short half-life mean a short effect?
Not always. Ipamorelin clears in two hours, while CJC-1295 raises IGF-1 for more than a week after one dose.
What is the half-life of BPC-157?
Not known. No human pharmacokinetic study of this peptide has been published.
Does HCG work better subcutaneously or intramuscularly?
In the 1991 study the testosterone, LH and FSH response was the same in both groups.
Do these figures tell you how often to give a peptide?
No. Half-life describes how a substance clears from the blood, not a protocol of use.
Sources
- Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical Research, 1999, 16(9): 1412-1416. https://doi.org/10.1023/a:1018955126402
- Teichman SL, Neale A, Lawrence B et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. Journal of Clinical Endocrinology and Metabolism, 2006, 91(3): 799-805. https://doi.org/10.1210/jc.2005-1536
- Yang XD, Yang YY. Clinical Pharmacokinetics of Semaglutide: A Systematic Review. Drug Design, Development and Therapy, 2024, 18: 2555-2570. https://doi.org/10.2147/DDDT.S470826
- Schneck K, Urva S. Population pharmacokinetics of the GIP/GLP receptor agonist tirzepatide. CPT: Pharmacometrics and Systems Pharmacology, 2024, 13(3): 494-503. https://doi.org/10.1002/psp4.13099
- Tetelbaun L, Mullally JA, Frishman WH. The First Triple Agonist for Antiobesity: Retatrutide. Cardiology in Review, 2024. https://doi.org/10.1097/CRD.0000000000000793
- Saal W, Glowania HJ, Hengst W, Happ J. Pharmacodynamics and pharmacokinetics after subcutaneous and intramuscular injection of human chorionic gonadotropin. Fertility and Sterility, 1991, 56(2): 225-229. https://pubmed.ncbi.nlm.nih.gov/1712735/