Half-Life Chart
Half-life is how long it takes for half the peptide to clear your system. It determines how often you need to dose. Here are the numbers for common peptides:
| Peptide | Approximate Half-Life | Typical Dosing Frequency |
|---|---|---|
| Semaglutide | 7 days (165-184 hours) | Weekly |
| Tirzepatide | ~5 days (120 hours) | Weekly |
| CJC-1295 (with DAC) | 6-8 days | Weekly |
| BPC-157 | Plasma t½ under 1 hour in rodent PK; effect window 4-6 hours | Daily or twice daily |
| TB-500 | No published synthetic human PK; community estimates 24-72 hours | 2-3x weekly |
| AOD-9604 | 6-8 hours | Daily |
| PT-141 | 2-3 hours | As needed (up to daily) |
| CJC-1295 (no DAC) / Ipamorelin | 30 minutes to 2 hours | Daily (often divided doses) |
| GHK-Cu | 1-2 hours | Daily or twice daily |
| Sermorelin | 30 minutes to 1 hour | Daily (often before sleep) |
| Selank | 2-3 hours | 2-3 times daily |
| Semax | 20-40 minutes | Multiple times daily |
| MOTS-c | 2-4 hours (limited data) | Daily |
These values are approximate. Your metabolism, injection site, and specific formulation will shift them.
How This Affects Your Schedule
Longer half-life means less frequent dosing. That part is obvious. The less obvious part: peptides clear on an exponential curve, not a cliff. After one half-life, 50% remains. After two, 25%. After three, 12.5%. A peptide is roughly 95% gone after 4-5 half-lives.
This matters for two reasons. First, short half-life peptides can still build up with repeated daily dosing. You're adding a new dose before the previous one fully clears, so tissue levels accumulate. Second, if you get side effects from a long half-life peptide (say, semaglutide at 7 days), those effects stick around for weeks after you stop.
Loading Phases
Some protocols use higher initial doses to saturate tissue faster, then drop to maintenance. This makes sense for peptides like TB-500 where you want to front-load tissue levels. For short half-life peptides like BPC-157, loading is less useful because steady-state levels build within a few days of consistent dosing anyway.
Stacking Different Half-Lives
When you combine peptides with different half-lives, keep the schedules separate. Example: Sermorelin (30-minute half-life) goes nightly before bed. Semaglutide (7-day half-life) goes once a week on whatever day you pick. Don't try to sync them.
Peptide-by-Peptide Breakdown
Weekly Dosing (7+ day half-life)
Semaglutide and Tirzepatide bind to albumin, which slows their clearance and keeps them active for about a week. One subcutaneous injection per week is all you need. The Semaglutide calculator handles the dose math.
CJC-1295 with DAC lasts 6-8 days thanks to its acylation modification. The non-DAC version (Mod GRF 1-29) has a half-life under 30 minutes and needs daily dosing. Same peptide name, completely different schedule.
Every 1-3 Days
TB-500 lacks published synthetic-peptide human pharmacokinetics. Community protocols estimate the effective window at 24-72 hours, which is why weekly doses are typically split across 2-3 injections (e.g., Monday/Wednesday/Friday). The TB-500 calculator helps with scheduling.
BPC-157 has a very short plasma half-life (under 1 hour in rodent PK; no published human PK), but its pharmacodynamic effects on tendon/gut tissues extend the practical dosing window. Daily or twice-daily dosing is the convention. The BPC-157 calculator covers reconstitution and dosing.
AOD-9604 at 6-8 hours fits here too. Daily dosing.
Daily or Multiple Times Daily
CJC-1295 without DAC + Ipamorelin: Both clear in under 2 hours. Daily dosing, often split morning and evening. The CJC-1295 Ipamorelin calculator covers this stack.
PT-141: 2-3 hour half-life, but used as-needed rather than on a fixed schedule. Effects last several hours. Once daily max. PT-141 calculator.
GHK-Cu: 1-2 hours. Daily or twice daily. GHK-Cu calculator.
Sermorelin: 30-60 minutes. Daily, usually before bed.
Selank: 2-3 hours. Two to three times daily.
Semax: 20-40 minutes. Multiple times daily.
MOTS-c: Limited data, but daily dosing is standard. MOTS-c calculator.
DSIP: Short half-life, dosed daily, typically before sleep.
Planning a Multi-Peptide Schedule
If you're running more than one peptide, group them by frequency:
- Weekly peptides (semaglutide, tirzepatide, CJC-1295 DAC): Pick a day and stick with it.
- Every-other-day peptides (TB-500): Set 2-3 fixed days per week.
- Daily peptides (BPC-157, AOD-9604, Ipamorelin): Same time each day.
- Multiple-daily peptides (Semax, Selank): Space evenly through the day.
If a peptide needs an empty stomach (most GH secretagogues do), schedule it 30-60 minutes before meals. If one causes drowsiness (DSIP, Sermorelin), move it to bedtime.
Storage Note
Daily-dosed peptides burn through vials faster. A 5mg BPC-157 vial at 500mcg/day lasts 10 days. A weekly semaglutide vial lasts a month or more. Plan your reconstitution accordingly, and check our storage guide for shelf life by peptide.
Missed Doses
If you miss a dose of a short half-life peptide, just take the next one on schedule. Don't double up. The peptide clears fast enough that doubling gives you a spike, not a catch-up.
With long half-life peptides (semaglutide, tirzepatide), a day or two late doesn't matter much. There's still plenty in your system. Take it when you remember and resume your normal schedule.
References
- Gobburu JV et al. "Pharmacokinetic-pharmacodynamic modeling of ipamorelin in human volunteers." Pharm Res, 1999. PubMed
- Teichman SL et al. "Prolonged stimulation of growth hormone and IGF-I by CJC-1295." J Clin Endocrinol Metab, 2006. PubMed
Disclaimer: These peptides are not FDA-approved for therapeutic use. Consult a healthcare provider before starting any peptide protocol.