What Is the Half-Life of a Peptide and Why Does It Matter?
A peptide's half-life is the time it takes for half the dose to break down in your body. This number tells you how often to inject and when to time doses so the peptide is actually active when you need it.
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What Does Half-Life Actually Mean?
When you inject a peptide, your body starts breaking it down right away.
After one half-life, half the dose is gone. After two half-lives, three-quarters is gone. After five half-lives, almost nothing remains.
A short half-life means the peptide clears quickly. A long half-life means it stays active for days.
Why Does Half-Life Shape Your Injection Schedule?
If a peptide clears in 2 hours, a single daily injection may not keep it active long enough to matter.
For short-half-life peptides, 2 or 3 injections per day is common. For long-half-life peptides, once or twice per week is enough.
Getting this wrong means either too little time in your system to work, or wasteful overlap between doses.
What Are the Half-Lives of Common Peptides?
These are general estimates. Half-life depends on the specific form, your metabolism, and how the peptide is made.
| Peptide | Estimated half-life | Typical injection frequency |
|---|---|---|
| BPC-157 | 30 minutes to 2 hours | 1 to 2 times daily |
| Ipamorelin | Roughly 2 hours | 2 to 3 times daily |
| CJC-1295 (no DAC) | Roughly 30 minutes | 2 to 3 times daily |
| CJC-1295 (with DAC) | Roughly 6 to 8 days | Once weekly |
| TB-500 | Several days | Once or twice weekly |
| Semaglutide | Roughly 7 days | Once weekly |
| Tirzepatide | Roughly 5 days | Once weekly |
Note: CJC-1295 "with DAC" stands for Drug Affinity Complex, a modification that extends the half-life dramatically by binding the peptide to albumin (a protein in your blood).
How Does Half-Life Affect Timing Around Training and Sleep?
For growth hormone (GH) releasing peptides, many users time injections to hit during deep sleep. This lines up the artificial GH pulse with the natural overnight GH release your body already makes.
That only works if you understand the half-life and inject at the right time before bed. Inject too early and the peak has already passed by the time you are in deep sleep.
For recovery peptides like BPC-157, timing is less critical because the goal is sustained tissue exposure, not a sharp pulse.
Half-life tells you whether spacing injections 4 hours apart or 24 hours apart makes more sense for what you are trying to accomplish.
Managing peptides with different half-lives at the same time can get complicated fast. DoseVault lets you log each peptide separately with its own timing and dose so you can see your full protocol in one place without things getting tangled.
Does the Injection Method Change the Half-Life?
Yes. A shot under the skin (subcutaneous) keeps a peptide active longer than a shot directly into a vein (intravenous) because the absorption is slower and more gradual.
Nasal sprays and oral forms of peptides generally have much shorter effective durations because the gut and nasal lining break them down quickly.
Most peptide users inject subcutaneously, which is why the estimates in the table above apply to that method specifically.
Disclaimer: This page is for educational purposes only and is not medical advice. Nothing here is intended to diagnose, treat, cure, or prevent any health condition. Consult a licensed clinician before using any peptide.
Managing multiple peptides with different timing needs? Keep it organized on DoseVault.