Peptide Half-Life Calculator
A peptide's half-life determines how quickly it is eliminated from the body and directly influences dosing frequency. This calculator helps you understand peptide decay curves and optimal injection timing.
Half-life is the time required for the concentration of a peptide in the bloodstream to decrease by 50%. After one half-life, 50% of the peptide remains; after two half-lives, 25% remains; after five half-lives, the compound is considered effectively eliminated (less than 3.125% remaining). This calculator models the decay curve for any peptide based on its known half-life, showing you the remaining concentration at any time point. It also calculates steady-state levels for repeated dosing protocols, helping optimize injection frequency for consistent blood levels.
How to Use
Select your peptide from the database or enter a custom half-life value in hours or minutes.
Enter your dose amount to see concentration levels over time.
View the decay curve graph showing peptide levels declining over time.
For repeated dosing, enter your injection frequency to see the steady-state concentration curve.
The calculator highlights the optimal dosing window to maintain therapeutic levels without excessive accumulation.
Formula
Remaining Amount = Initial Dose x (0.5)^(Time Elapsed / Half-Life). Steady State Level = Dose / (1 - 0.5^(Dosing Interval / Half-Life)).Example
BPC-157 has an estimated half-life of approximately 4 hours. Starting with a 250mcg dose: after 4 hours, 125mcg remains; after 8 hours, 62.5mcg remains; after 12 hours, 31.25mcg remains. This short half-life is why many protocols call for twice-daily dosing to maintain consistent levels.
Frequently Asked Questions
How does half-life affect dosing frequency?
Shorter half-life peptides require more frequent dosing to maintain stable blood levels. For example, a peptide with a 2-hour half-life may need dosing 2-3 times daily, while CJC-1295 with DAC has a half-life of 6-8 days and is typically dosed once or twice weekly. The general rule is to dose at intervals of 1-2 half-lives for consistent levels.
What is steady state in peptide dosing?
Steady state occurs when the rate of peptide administration equals the rate of elimination. At steady state, blood levels fluctuate within a predictable range with each dose. Most peptides reach approximate steady state after 4-5 half-lives of repeated dosing. This is why some protocols have a loading phase with higher initial doses.
Why do some peptides have different half-lives by route of administration?
The route of administration affects absorption rate and bioavailability. Subcutaneous injection creates a depot effect where the peptide is slowly absorbed from the injection site, effectively extending the apparent half-life compared to intravenous administration. Oral peptides typically have much shorter effective half-lives due to digestive degradation.