# Peptide Half-Life Explained: Why It Matters for Your Dosing Schedule

Source: https://www.trackpep.com/blog/peptide-half-life-explained

> Educational information only. Not medical advice, and not a dosing recommendation. TrackPep records what you enter and converts a dose you were prescribed into a syringe reading; it never decides a dose for you. Talk to a licensed clinician.

Half-life determines how long a compound stays active in your body. Understanding it helps you dose smarter and avoid accumulation.

If you have spent any time reading about peptides, you have seen the term "half-life." It sounds technical, but the basic concept is simple — and it has real implications for your dosing schedule.

## What is half-life?

Half-life (t½) is the time it takes for the concentration of a compound in your blood to drop by 50%. After one half-life, 50% remains. After two, 25%. After three, 12.5%. After about five half-lives, the compound is effectively eliminated from your body.

## Why it matters for dosing

**Short half-life (≤ 2 hours)** — Compounds like GHRP-2, ipamorelin, and sermorelin need multiple daily doses to maintain effect. Dose timing relative to meals becomes critical because glucose suppresses GH release.

**Medium half-life (2–24 hours)** — Liraglutide (13 h) fits here. Once-daily dosing works. Miss a dose and you feel it the next day.

**Long half-life (≥ 100 hours)** — Semaglutide (165 h) and tirzepatide (120 h) are once-weekly. Steady state takes 4–5 weeks to reach. Dose changes take weeks to show full effect — and side effects can linger.

## Steady state

With repeated dosing at regular intervals, the drug concentration builds up until it reaches a plateau called steady state. For once-weekly GLP-1s, this happens around week 4–5. That means the full glycaemic and weight-loss benefit may not appear immediately — patience is required.

## Practical takeaways

- Map your dosing schedule to the compound's half-life — not the other way around.
- When switching doses, allow 5 half-lives to reach a new steady state before judging efficacy.
- Track consistently. A 7-day log won't tell you much about a compound with a 7-day half-life; you need 4–8 weeks of data.

TrackPep calculates half-life-based scheduling automatically when you log a compound, and it shows your estimated blood concentration over time.

By TrackPep Team.