Half-Life Visualizer & Calculator

See how medication levels rise and fall between injections. Switch compounds, change the dose and schedule, watch the curve respond in real time.

Active levels

Semaglutide

Half-life 7.0 days·tMax 34h

SourceFDA Ozempic label (NDA 209637)

Compound

Dose per injection

Schedule

Window

Estimated active level

Dose

Steady-state band

Steady-state peak

1.79mg

Trough

1.03mg

Trough as % of peak

58%

Time to steady state

~5wks

Keep your compounds in Regimen and see your levels between doses.Add to Regimen

Population-average pharmacokinetic model. Individual variation is significant. Not medical advice. See the methodology.

This tool is for informational purposes only, so always double-check your result with a healthcare provider. Levels shown are estimates from a population-average pharmacokinetic model, not a dosing recommendation, and individual variation is significant. We assume no liability for dosing errors.

The tool

How it works, what it tells you, what it doesn't.

The half-life visualizer maps the pharmacokinetic curve: how drug levels in your blood peak after injection, then gradually decline until the next dose. Understanding this curve helps you choose an injection frequency, time bloodwork meaningfully, and explain why you feel different at different points in your dosing cycle. Testosterone cypionate (half-life about 6.9 days) produces wider swings on weekly injections than on every-other-day or daily protocols. GLP-1s like semaglutide (half-life around 7 days) are remarkably stable week to week. This calculator uses the same Bateman model the Regimen app uses, calibrated to each compound's published half-life and time-to-peak.

How to use it

How to Use This Visualizer

01

Select a compound

Choose from semaglutide, tirzepatide, testosterone, BPC-157, and more
02

Enter your dose

The amount you take per administration in mg, mcg, or IU
03

Set frequency and start date

How often you dose and when you started your protocol
04

View the curve

See blood concentration with peak, steady state, and clearance estimates

How This Visualizer Works

This tool uses the Bateman equation, a one-compartment pharmacokinetic model that accounts for both absorption and elimination phases. Unlike simple exponential decay calculators, the Bateman model creates a realistic curve that starts at zero, rises as the compound absorbs into your bloodstream, peaks at Tmax, and then gradually declines.

When you dose repeatedly, the tool uses superposition to sum the contribution of every previous dose at each point in time. This shows how levels accumulate with consistent dosing and eventually reach a steady state where peak and trough levels stabilize.

The key parameters for each compound are half-life (how quickly the compound is eliminated), Tmax (time to peak absorption), and the absorption rate constant (derived from these values). All parameters are based on published clinical data and FDA prescribing information.

Data Sources

This tool uses dosing information from official prescribing information:

Semaglutide - FDA NDA 209637 (Ozempic prescribing information), half-life ~7 days
Tirzepatide - FDA NDA 215866 (Mounjaro prescribing information), half-life ~5 days
Retatrutide - Phase 2 clinical trial data (Jastreboff et al., NEJM 2023), half-life ~6 days
Testosterone Cypionate - Published pharmacokinetic literature (PMC5915615, DrugBank), terminal half-life ~6.9 days (166 hours). Enanthate uses the same value.
BPC-157 - Published research literature, estimated half-life ~5 hours
TB-500 - Published research literature (Thymosin Beta-4), estimated half-life ~2 hours
HGH (Somatropin) - FDA-approved prescribing information, half-life ~4 hours

Get the app

See your personal curve in the app

Regimen logs every injection and builds your personal pharmacokinetic curve, with site rotation, lab work tracking, and Apple Health correlation.

Visualize any compound you're tracking
See current blood levels and clearance
Smart injection reminders
Private, secure health data

Free to download. Free for your first compound.

Regimen app Today view with doses and estimated levels

Questions

Frequently Asked Questions

What is a half-life?

Half-life is the time it takes for the concentration of a substance in your body to decrease by 50%. After one half-life, half the dose remains. After two half-lives, 25% remains. This determines how often you need to dose to maintain therapeutic levels.

How does this visualizer calculate blood levels?

This tool uses the Bateman equation, a pharmacokinetic model that accounts for both absorption and elimination. Unlike a simple decay curve, the Bateman model realistically shows your levels starting at zero, rising as the compound absorbs, peaking at Tmax, and then gradually declining. Multiple doses are layered (superposition) to show how levels accumulate over days or weeks of consistent dosing.

Why does the curve rise before it falls?

After you take a dose, the compound needs time to absorb into your bloodstream. This absorption phase creates the upward slope. The peak (Tmax) is when absorption rate equals elimination rate. After that, elimination dominates and levels decline. For example, semaglutide takes about 2 days to reach peak levels after injection.

What is steady state and how long does it take?

Steady state occurs when the amount of compound being absorbed from new doses equals the amount being eliminated. At steady state, your peak and trough levels remain consistent between doses. It takes approximately 5 half-lives of regular dosing to reach steady state. For semaglutide (7-day half-life), that is about 5 weeks.

How long until a compound is fully out of my system?

A compound is considered effectively cleared after about 5 half-lives, when less than 3% remains. For BPC-157 (5-hour half-life), that is about 25 hours. For semaglutide (7-day half-life), that is about 5 weeks. For testosterone cypionate (~6.9-day half-life), that is about 5 weeks.

Why does BPC-157 need to be dosed more frequently?

BPC-157 has a very short half-life of approximately 5 hours, meaning it clears your system relatively quickly. This is why it is typically dosed twice daily (every 12 hours) to maintain more consistent levels throughout the day, unlike weekly compounds like semaglutide.

What does the peak level number mean?

The peak level shown represents the highest estimated concentration in your system based on your dose and the compound's absorption profile. The Y-axis shows relative concentration scaled to your dose amount, not an actual blood test number. Real blood levels depend on individual factors like metabolism, body composition, and injection site.

Can I use this for compounds not listed?

This web tool includes the 7 most commonly tracked compounds. If you need to visualize other compounds, the Regimen app lets you track any compound with custom half-life and dosing parameters, and see your real-time blood levels based on your actual logged doses.

How accurate is this visualization?

This tool uses a simplified one-compartment pharmacokinetic model based on published half-life and absorption data. It provides a useful approximation, but real blood levels vary based on individual metabolism, body composition, injection site, formulation, and other factors. Always consult your healthcare provider for clinical decisions.