Which peptide has the longest half-life?

Among commonly used peptides and compounds, semaglutide has the longest half-life at approximately 161 hours (6.7 days), which allows for once-weekly dosing. CJC-1295 with DAC has a half-life of about 192 hours (8 days). Among testosterone esters, testosterone undecanoate has the longest at approximately 1,272 hours (53 days).

Peptide & Compound Half-Life Chart — Complete Comparison

What Is Half-Life?

In pharmacokinetics, half-life is the time it takes for the concentration of a compound in your blood to decrease by exactly 50%. It is one of the most important parameters governing how a compound behaves in your body.

Half-life directly determines dosing frequency. Compounds with short half-lives (like BPC-157 at 30 minutes) are typically dosed daily because they clear quickly. Compounds with long half-lives (like semaglutide at 6.7 days) can be dosed once a week because they remain active for extended periods.

Time to Steady State ≈ 5 × t½

Steady state is reached after approximately 5 half-lives of consistent dosing. At this point, the amount of compound entering your system equals the amount being cleared with each dose cycle. This is when blood levels stabilize into a predictable pattern and the compound reaches its full pharmacokinetic potential.

The range of half-lives across commonly used compounds is enormous — from 15 minutes (glutathione) to 53 days (testosterone undecanoate). This 5,000x range is why dosing frequency varies so dramatically between compounds and why tracking levels matters.

Steady-State Reference Table

Time to reach steady state (5 × half-life) and typical dosing frequency for each compound.

Compound ▲	Half-Life ▼	Steady State ▲	Typical Frequency
Testosterone Undecanoate	1,272h (53d)	265 days	Every 10-14 weeks
CJC-1295 with DAC	192h (8d)	40 days	1-2x per week
Testosterone Cypionate	192h (8d)	40 days	1-2x per week
Semaglutide	161h (6.7d)	33.5 days	Once weekly
Tirzepatide	120h (5d)	25 days	Once weekly
Retatrutide	120h (5d)	25 days	Once weekly
Testosterone Enanthate	108h (4.5d)	22.5 days	1-2x per week
Testosterone Propionate	19h	4 days	Every other day
GHK-Cu	4h	20 hours	Once daily
PT-141	2.5h	12.5 hours	As needed
TB-500	2h	10 hours	Once daily
Ipamorelin	2h	10 hours	2-3x daily
NAD+	45 min	3.75 hours	Once daily
BPC-157	30 min	2.5 hours	1-2x daily
CJC-1295 no DAC	30 min	2.5 hours	2-3x daily
Glutathione	15 min	1.25 hours	Once daily

Frequently Asked Questions

Common questions about compound half-lives and pharmacokinetics.

What is a compound half-life?

A compound's half-life is the time it takes for the concentration in your body to decrease by 50%. For example, if a peptide has a 2-hour half-life, half of the administered dose will be cleared after 2 hours, 75% after 4 hours, 87.5% after 6 hours, and so on. This is a fundamental pharmacokinetic parameter that determines how long a compound remains active and how frequently it needs to be administered.

How does half-life affect dosing frequency?

Compounds with shorter half-lives need more frequent dosing to maintain stable blood levels. A peptide with a 30-minute half-life (like BPC-157) is typically dosed daily, while a GLP-1 agonist with a 161-hour half-life (like semaglutide) can be dosed once weekly. The goal is to maintain therapeutic levels without excessive peak-to-trough variation. Shorter half-life compounds naturally have wider swings between peak and trough levels.

How long does it take to reach steady state?

Steady state is reached after approximately 5 half-lives of consistent dosing. At this point, the amount entering the body equals the amount being cleared with each dose cycle. For testosterone enanthate (108h half-life), steady state takes about 22.5 days. For semaglutide (161h half-life), it takes approximately 33.5 days or about 5 weeks. This is why it often takes several weeks before you can fully evaluate how a protocol is performing.

Why do some peptides have such short half-lives?

Many peptides are rapidly broken down by enzymes in the blood (proteases) and cleared by the kidneys due to their small molecular size. This is why peptides like BPC-157 (30 min), glutathione (15 min), and CJC-1295 without DAC (30 min) have very short half-lives. Modified versions — like CJC-1295 with DAC — use chemical modifications (Drug Affinity Complex) to resist enzymatic breakdown, extending the half-life dramatically from 30 minutes to 8 days.

Which compound has the longest half-life?

Among the compounds tracked in this chart, testosterone undecanoate has the longest half-life at approximately 1,272 hours (53 days), primarily used in long-acting injectable TRT formulations. Among peptides and GLP-1 agonists, CJC-1295 with DAC (192h / 8 days) and semaglutide (161h / 6.7 days) have the longest half-lives, which is why both can be administered on a weekly or less frequent schedule.

Does route of administration affect half-life?

The route of administration can influence the effective half-life by changing the absorption rate. Subcutaneous injections create a depot effect that slows absorption, effectively extending the duration of action compared to intravenous administration. Oral peptides generally have shorter effective half-lives due to first-pass metabolism in the liver. The half-life values shown in this chart reflect the most common route of administration for each compound.

CompoundHalf-Life Chart

What Is Half-Life?

Steady-State Reference Table

Frequently Asked Questions

Compound Pages

Compound
Half-Life Chart