Compare half-lives, dosing frequency, and what each peptide is commonly used for at a glance.
| Peptide | Half-Life | Typical Dosing Frequency |
|---|---|---|
| RetatrutideUsed for: weight loss | ~6 days | Once weekly |
| SemaglutideUsed for: weight loss and appetite control | ~7 days | Once weekly |
| TirzepatideUsed for: weight loss and blood sugar control | ~5 days | Once weekly |
| CJC-1295 with DACUsed for: growth hormone support | ~8 days | 2x weekly |
| TB-500Used for: recovery and tissue repair | ~24 hours | 2-3x weekly |
| MOTS-cUsed for: metabolic support and energy | ~12-24 hours | 3-5x weekly |
| AOD-9604Used for: fat-loss support | ~4-6 hours | 1x daily |
| GHK-CuUsed for: skin, hair, and tissue repair | ~4-6 hours | 1x daily |
| BPC-157Used for: healing and gut support | ~4 hours | 1-2x daily |
| PT-141Used for: sexual health support | ~2-4 hours | As needed |
| IpamorelinUsed for: growth hormone pulses | ~2 hours | 1-3x daily |
| CJC-1295 no DACUsed for: GH pulse support | ~30 min | 1-3x daily |
A peptide's half-life determines how often you need to inject it to maintain effective levels in your body. Peptides with short half-lives (like CJC-1295 no DAC at ~30 minutes) need to be dosed multiple times per day, while long half-life peptides (like semaglutide at ~7 days) only require weekly injections.
Understanding half-life also helps with timing. Short half-life peptides produce sharp, pulsatile effects that are ideal when you want to mimic natural hormone patterns (like the growth hormone pulse from CJC+Ipamorelin before bed). Long half-life peptides create steady, sustained levels that provide consistent appetite suppression (like semaglutide).
Half-life and duration of effect are not the same thing. A peptide's effects can last well beyond its half-life because the biological processes it triggers continue after the peptide itself has been cleared. For example, BPC-157 has a ~4 hour half-life but its healing effects accumulate over weeks of consistent dosing.
Half-life is the time it takes for the concentration in the bloodstream to fall by half. It is not the time until the compound is gone. After one half-life you have 50 percent remaining, after two you have 25 percent, after three about 12.5 percent, and so on.
The practical rule that follows: a compound is essentially cleared after roughly four to five half-lives. For semaglutide at about 7 days, that means something in the range of 5 weeks before it is substantially out of the system. For BPC-157 at about 4 hours, it is under a day. This is why stopping a weekly GLP-1 does not produce an immediate change, while stopping a short-acting peptide does.
The same math explains why steady levels take time to build. Reaching a stable concentration on a repeated schedule also takes about four to five half-lives. A weekly compound with a 7 day half-life is therefore still climbing toward its plateau more than a month into a protocol, which is one reason dose escalation schedules are spread over months rather than weeks.
If frequency were purely a function of half-life, everything in the table above would line up neatly. It does not, and the exceptions are informative.
CJC-1295 no DAC has a roughly 30 minute half-life but is dosed one to three times daily, not hourly. That is deliberate. The goal is to trigger a growth hormone pulse that mimics natural secretion, and natural GH release is pulsatile rather than continuous. A short half-life is the feature, not a limitation to be worked around. Continuous elevation would actually defeat the purpose, since the receptors respond to the pulse pattern.
BPC-157 has a roughly 4 hour half-life but is commonly dosed once or twice daily. Here the reasoning is that the repair processes it is thought to influence, such as angiogenesis and tissue remodeling, operate on a timescale of days and weeks. Keeping blood levels constant is not the objective, so the dosing interval is set by the biological process rather than by plasma concentration.
The GLP-1 compounds are the case where half-life genuinely drives the schedule. Semaglutide at about 7 days and tirzepatide at about 5 days are both long enough that once-weekly administration keeps levels within a workable band. That is a design goal of those molecules rather than an accident, since weekly dosing improves adherence substantially compared to daily injections.
The right response to a missed dose depends heavily on where the compound sits in this table, which is another reason the number matters.
For a short half-life peptide, a missed dose is largely self-correcting. Levels were going to fall to near zero between doses anyway, so resuming on the next scheduled dose returns you to the normal pattern without any accumulation concern.
For a long half-life weekly compound the situation is different, because doses overlap. Levels from the previous injection are still meaningful when the next one is due. Taking a missed dose late and then taking the next one on the original schedule can stack them closer than intended. Approved GLP-1 labeling gives specific guidance on this, generally allowing a late dose within a defined window and otherwise skipping to the next scheduled one. That guidance belongs to the product labeling and to a prescribing clinician, not to a chart.
Related references: storage guide, injection sites, and the reconstitution calculator.