Peptide Half-Life Reference Guide: Complete Research Compound Duration Database

Comprehensive half-life reference table for 20+ research peptides including BPC-157, TB-500, Ipamorelin, CJC-1295 DAC, Semaglutide, Tirzepatide, and more. Understand how half-life determines dosing frequency and injection scheduling.

TL;DR

• Half-life determines how often a peptide must be dosed to maintain therapeutic plasma concentrations
• Short-acting peptides (MOD GRF, Semax) require timing precision; long-acting ones (CJC DAC, Semaglutide) allow weekly dosing
• Albumin binding and PEGylation are common strategies used to extend peptide half-lives
• After 5 half-lives, a peptide is ~97% eliminated from plasma
• Use the half-life calculator to model your specific dosing schedule

Disclaimer: For educational and research purposes only — not medical advice.

Half-life is the single most important pharmacokinetic parameter for designing a peptide research protocol. It determines injection frequency, governs whether a compound achieves steady-state or peaks and troughs, and dictates whether pulsatile or continuous receptor stimulation is occurring. Despite its importance, half-life data for research peptides is often scattered across animal studies, phase I human trials, and anecdotal reports — with wide variability depending on route of administration, formulation, and individual metabolism.

This reference compiles half-life data for more than 20 commonly researched peptides, explains the mechanisms behind half-life extension, and provides practical guidance on translating pharmacokinetic data into dosing schedules.

Understanding Peptide Half-Life: Pharmacokinetic Basics

Half-life (t½) is defined as the time required for the plasma concentration of a compound to decrease by 50%. For most peptides and proteins, elimination follows first-order kinetics, meaning the rate of elimination is proportional to the current concentration.

Key derived values:

• Time to steady-state: Approximately 4-5 half-lives of regular dosing
• Time to elimination: Approximately 5 half-lives (97% cleared)
• Trough concentration: Minimum plasma level before next dose

For peptides, half-life is determined by:

1. Proteolytic degradation — plasma and tissue peptidases cleave peptides; this is the dominant elimination route for most unmodified peptides
2. Renal filtration — small peptides (<5kDa) are filtered at the glomerulus
3. Receptor-mediated endocytosis — binding and internalization by target receptors
4. Modification strategies — DAC linkers, PEGylation, fatty acid conjugation (acylation), and cyclization all extend half-life by reducing proteolysis

Master Half-Life Reference Table

All values are approximate and derived from animal pharmacokinetic studies or limited human PK data. Individual variation is significant.

How Half-Life Engineering Works

Modern peptide pharmacology employs several strategies to extend the native half-life of peptides that would otherwise be rapidly degraded:

Albumin Binding (DAC Technology)

CJC-1295 DAC is the most prominent example in research peptide circles. The Drug Affinity Complex (DAC) technology adds a maleimide-modified lysine residue that spontaneously reacts with the free thiol on albumin's Cys-34. Since albumin has an ~19-day half-life, any compound covalently attached to it adopts a dramatically extended half-life. The result: MOD GRF (30 min) becomes CJC-1295 DAC (8 days).

Fatty Acid Acylation

Semaglutide's 7-day half-life is achieved by conjugating a C18 fatty diacid chain via a linker to GLP-1. This enables reversible albumin binding, which protects the peptide from DPP-IV degradation and renal clearance. Tirzepatide uses a similar C18 fatty diacid strategy applied to a dual GIP/GLP-1 scaffold.

PEGylation

Polyethylene glycol chains attached to peptides increase hydrodynamic radius (preventing renal filtration), reduce proteolytic access, and lower immunogenicity. PEG-MGF (PEGylated mechano growth factor) achieves a ~72-hour half-life vs. the ~minutes half-life of native MGF.

D-Amino Acid Substitution

Some research peptides incorporate D-amino acids (mirror-image enantiomers of the L-amino acids used in natural proteins). Proteases are stereospecific — they cannot efficiently cleave D-amino acid bonds, so D-substituted peptides resist enzymatic degradation. Selank and several cyclized peptides use this approach.

Cyclization

Cyclic peptides are inherently more resistant to exopeptidase degradation because they lack free N- and C-termini. Many naturally occurring bioactive peptides (oxytocin, cyclosporine) are cyclic for this reason.

Route of Administration and Half-Life

Route of administration affects both peak concentration (Cmax) and effective duration:

Subcutaneous injection creates a local depot effect that slows release into systemic circulation, effectively extending the time to peak and smoothing out the plasma concentration curve compared to IV. This is why SC half-life values often appear slightly longer than IV-derived values for the same compound.

Practical Dosing Schedule Design

Using half-life data to design a protocol:

Example: Ipamorelin + MOD GRF (the most common GHRP/GHRH pairing)

• Ipamorelin t½: ~2 hours → clears in ~10 hours
• MOD GRF t½: ~30 min → clears in ~2.5 hours
• Protocol logic: Both are dosed simultaneously to create a synergistic GH pulse; typical frequency is 2-3x daily (morning, post-workout, bedtime) because each dose is effectively eliminated before the next
• Neither compound accumulates to steady state — each injection creates an acute pulse

Example: CJC-1295 DAC (weekly protocol)

• t½: ~8 days → steady state achieved after ~5-6 weeks of weekly dosing
• Protocol logic: Weekly injection maintains sustained GHRH stimulation; GH release is not pulsatile but rather tonically elevated
• Important consideration: Tonic GHRH elevation may reduce pituitary sensitivity over time compared to pulsatile signaling

Example: Semaglutide (weekly GLP-1 protocol)

• t½: ~7 days → doses taken weekly maintain very stable plasma concentrations (< 30% peak-to-trough fluctuation)
• Steady state: Achieved at approximately week 4-5
• Protocol logic: Weekly injection on the same day each week; dose escalation typically every 4 weeks

Frequently Asked Questions

Q: Does subcutaneous injection extend a peptide's half-life? A: Subcutaneous injection does not change the intrinsic elimination half-life of a peptide, but it does create a depot from which the peptide is absorbed slowly into systemic circulation. This extends the time to peak concentration and the overall duration of action compared to IV injection, but once absorbed, the peptide clears at its characteristic rate. The practical effect is a smoother, longer plasma curve from SC compared to IV for the same dose.

Q: Why do GHRPs have such short half-lives? A: GHRPs (growth hormone releasing peptides) like GHRP-2, GHRP-6, and Ipamorelin are short oligopeptides (6-7 amino acids) that are rapidly degraded by plasma peptidases and renal filtration. Their short half-lives are actually considered a feature rather than a bug — they allow for pulsatile GH stimulation that mimics natural GH release patterns, which is physiologically important for maintaining receptor sensitivity and IGF-1 production.

Q: How long after my last dose of CJC-1295 DAC will it be cleared? A: With an ~8-day half-life, CJC-1295 DAC requires approximately 5 half-lives (40 days) to be 97% cleared from plasma. This is important context for planning protocol breaks or transitions — a single injection continues to exert GHRH-like effects for over a month.

Use the Half-Life & Dosing Calculator [→ /calculators/dosage]

For educational and research purposes only. Not medical advice.

Disclaimer: For educational and research purposes only. Nothing in this article constitutes medical advice, diagnosis, or treatment recommendation. All compounds discussed are research chemicals or investigational compounds unless explicitly noted otherwise. Consult a qualified healthcare professional before making any health-related decisions. Researchers must comply with all applicable laws and regulations in their jurisdiction.

Frequently Asked Questions