How long does a compound stay in your system based on its half-life?

After each half-life, half of the remaining amount is gone: one half-life leaves 50%, two leave 25%, three leave 12.5%, and roughly five half-lives leave about 3% — the point where a drug is usually considered practically cleared.

Why do peptide half-lives vary so much?

Half-life depends on the molecule and how it is engineered. Native peptides are often cleared in minutes, while modified analogues designed to resist enzymes or bind albumin — such as the once-weekly GLP-1 drugs — can persist for days.

Peptide Half-Life Visualizer

Half-life

Preset (approximate)Presets are approximate; always prefer a value you trust.

Half-life value

Half-life unit

Time since dose

Read the amount remaining at this point.

Remaining after 5 hr

50 %

of the original dose

50% remaining (1 half-life)—

25% remaining (2 half-lives)—

10% remaining (~3.3 half-lives)—

1% remaining (~6.6 half-lives)—

Practically cleared (~5 half-lives)—

How this works

Methodology reviewed July 2026

The tool models a single dose leaving the body by first-order (exponential) clearance, the standard textbook approximation for most drugs once absorption is complete. The elimination rate constant λ is derived from the half-life as ln(2) divided by t½, and the fraction remaining at any time is 100·e^(−λt). Every milestone follows directly: 50% remains after one half-life, 25% after two, and because each half-life removes half of what is left, roughly five half-lives bring the amount to about 3% — the conventional point at which a drug is treated as practically eliminated. The curve simply plots that equation from the moment of dosing out to about 5.5 half-lives.

Formula

λ            = ln(2) / half_life
remaining(t) = 100 × e^(−λ·t)          (percent of original dose)
time to X%   = half_life × ln(100 / X) / ln(2)

Inputs

Half-life (min · hours or days) · Time since dose · Optional approximate preset

Outputs

Clearance curve · Percent remaining at a chosen time · Time to 50% · 25% · 10% and 1% remaining

Assumptions

Clearance is first-order and mono-exponential, so a fixed fraction is removed per unit time regardless of the starting amount.
The model starts after absorption is complete; it does not draw the rise to peak concentration that follows a subcutaneous injection.
The half-life entered is the elimination half-life and is constant across the concentration range shown.
The amount in the body is treated as a single well-mixed pool; distribution between tissues is ignored.

Limitations

Real pharmacokinetics are often multi-phase (a fast distribution phase then a slower elimination phase), so a single exponential is an approximation.
Preset half-lives are approximate values from labels and published literature; many research peptides have poorly characterized or highly variable human half-lives, and some values are debated.
The visualizer shows clearance from the bloodstream, which is not the same as duration of biological effect — a compound can act after most of it has cleared, or persist in effect beyond measurable levels.
It models one dose in isolation; repeated dosing accumulates and is better explored with the dose interval visualizer.

Safety

Half-life is not a measure of safety or of when a compound is "safe" to redose; use it to understand clearance, not to schedule doses.
Clearance from blood does not equal loss of effect or of risk — do not infer that a drug is inactive simply because levels are low.
Many research peptides are not approved for human use; this tool is a clearance model for education only and not a recommendation to obtain, prepare, or use any peptide.

This calculator is for educational purposes only and is not medical advice, diagnosis, or treatment. Results are estimates based on published formulas and population averages — your individual values may differ. Nothing here is calculated on a server: everything runs in your browser and no data is stored or sent anywhere. Always consult a qualified clinician before making health, medication, or training decisions.