Peptide Half-Life Tracker
Visualize peptide decay curves and compare half-lives side by side. Select up to 5 peptides to see how their concentrations change over time.
Tap to select or deselect. Maximum 5 peptides at a time.
Select one or more peptides above to visualize their decay curves.
What is Peptide Half-Life?
Half-life is the time it takes for the concentration of a peptide in your bloodstream to drop to 50% of its initial level after administration. For example, if you inject a peptide with a 4-hour half-life, after 4 hours only half the original amount remains active. After another 4 hours (8 hours total), only 25% remains, and so on. This exponential decay pattern is fundamental to understanding how peptides behave in the body and directly determines how long their effects last.
Half-life is the most important factor in determining dosing frequency. Peptides with short half-lives (under 2 hours) like CJC-1295 (no DAC), Semax, and Selank require multiple daily administrations to maintain therapeutic levels. Peptides with longer half-lives such as semaglutide (7 days) or CJC-1295 with DAC (8 days) only need to be injected once per week. Understanding half-life helps you plan an effective and convenient dosing schedule while avoiding both underdosing and unnecessary excess.
It is important to distinguish between plasma half-life and the duration of biological effect. Plasma half-life measures how quickly the peptide is cleared from your blood, but many peptides trigger downstream cellular processes that continue long after the compound itself has been eliminated. BPC-157, for example, has a relatively short plasma half-life of about 4 hours, yet the healing cascades it initiates (including angiogenesis, collagen repair, and growth factor upregulation) persist well beyond that window. This is why some peptides appear to "work" for much longer than their half-life would suggest. When building a peptide stack, comparing decay curves helps align injection schedules across compounds. For dosage specifics, check our dosage charts.
How to Read the Chart
- 1.The vertical axis (Y-axis) represents the concentration of the peptide as a percentage of the initial dose, ranging from 100% (full dose at time of injection) down to 0%. The horizontal axis (X-axis) represents time elapsed since administration.
- 2.Each colored curve represents a different peptide. The steeper the curve drops, the shorter the half-life and the faster the peptide is cleared from the body. A flat, slowly declining curve indicates a long half-life.
- 3.Find the point where a curve crosses the 50% line on the Y-axis. The corresponding time on the X-axis is that peptide's half-life. For example, if a curve hits 50% at 4 hours, its half-life is 4 hours.
- 4.Use the time range buttons to zoom in or out. Short-acting peptides (Semax, CJC-1295 no DAC) are best viewed on the 12-hour scale, while long-acting peptides (Semaglutide, CJC-1295 DAC) are best compared on the 7-day or 14-day scale.
Half-Life Quick Reference
| Peptide | Half-Life | Typical Dosing |
|---|---|---|
| BPC-157 | 4h | 2-3x daily |
| TB-500 | 3 days | 2-3x per week |
| Semaglutide | 7 days | Once weekly |
| Tirzepatide | 5 days | Once weekly |
| CJC-1295 (DAC) | 8 days | Once weekly or less |
| CJC-1295 (no DAC) | 30 min | Multiple times daily |
| Ipamorelin | 2h | 2-3x daily |
| HGH Fragment 176-191 | 1h | 2-3x daily |
| Retatrutide | 6 days | Once weekly |
| PT-141 | 4h | 2-3x daily |
| Semax | 20 min | Multiple times daily |
| Selank | 30 min | Multiple times daily |
| Epitalon | 2h | 2-3x daily |
| AOD-9604 | 1h | 2-3x daily |
Frequently Asked Questions
Does a longer half-life mean the peptide is better?
Not necessarily. A longer half-life simply means the peptide stays active in your body for a longer period, which typically translates to less frequent dosing. However, effectiveness depends on many factors including receptor affinity, bioavailability, and how well the peptide matches your specific goals. Short-acting peptides like CJC-1295 (no DAC) can be advantageous because they mimic the body's natural pulsatile release patterns, which may be more physiologically beneficial for certain applications like growth hormone stimulation.
Why do some peptides seem to work longer than their half-life suggests?
A peptide's half-life measures how quickly its concentration drops in the bloodstream, but this does not always correlate directly with its duration of effect. Some peptides trigger downstream biological processes that continue long after the peptide itself has been cleared. For example, BPC-157 has a plasma half-life of about 4 hours, but it initiates healing cascades (angiogenesis, collagen synthesis, growth factor upregulation) that persist for much longer. Similarly, growth hormone secretagogues cause a pulse of GH release that has metabolic effects lasting well beyond the peptide's presence in the blood.
How does half-life affect injection frequency?
Half-life is the primary factor determining how often you need to dose a peptide to maintain effective blood levels. The general rule is that you want to redose before the peptide drops below its therapeutic threshold. For short half-life peptides (under 2 hours), this means multiple daily injections. For medium half-life peptides (4-24 hours), once or twice daily dosing is typical. For long half-life peptides (several days), weekly or even less frequent dosing is sufficient. Semaglutide's 7-day half-life is what makes once-weekly injection possible.
Does the half-life change with repeated dosing?
The intrinsic half-life of a peptide does not change with repeated dosing, but the effective concentration profile does. With repeated dosing, each new dose adds to the remaining concentration from previous doses, creating an accumulation effect until the body reaches what is called steady state. At steady state, the amount of peptide eliminated between doses equals the amount administered. This is why some peptides like semaglutide require a titration period, as the drug accumulates over several weeks before reaching its full therapeutic level.
What is steady state and why does it matter?
Steady state is the point at which the rate of peptide administration equals the rate of elimination, resulting in a consistent average concentration in the body. It typically takes about 4-5 half-lives to reach steady state. For a peptide like semaglutide (half-life of 7 days), this means approximately 4-5 weeks of consistent weekly dosing. Understanding steady state is important because it explains why some peptides take weeks to reach full effectiveness and why dose changes take time to manifest. It also explains why you should not judge a peptide's effectiveness until you have been using it long enough to reach steady state.
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