How often should you inject Zepbound?

Zepbound is typically injected once weekly due to its long half-life of approximately 5 days.

How long until Zepbound reaches steady state?

With a half-life of approximately 5 days, Zepbound reaches steady state after about 4-5 weeks of consistent weekly dosing. Steady state means drug levels stabilize with consistent peaks and troughs.

Stability Window Details

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Average stable amount: - mg

Stable window days

Date	Day	Amount in Body

Zepbound Calculator: Track Dose Levels & Reach Steady State

// HOW IT WORKS

How the Zepbound Calculator Works

This free Zepbound calculator uses pharmacokinetic modeling to track your tirzepatide levels over time. Enter your dose and schedule to see how the drug builds up in your system.

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Zepbound Half-Life Calculator

With a 5-day half-life, see how concentration peaks after each injection and decreases between doses.

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Steady State Prediction

Know when you'll reach steady state (typically 4 weeks on Zepbound) where drug levels stabilize for optimal weight loss.

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Visualize Drug Levels

Interactive chart shows tirzepatide concentration from 2.5mg through your target maintenance dose.

Zepbound Dosing Guide

Zepbound (tirzepatide) is an FDA-approved once-weekly injectable for chronic weight management. It's the same active ingredient as Mounjaro, but approved for adults with obesity (BMI ≥30) or overweight (BMI ≥27) with at least one weight-related condition. In the SURMOUNT-1 trial, the 15mg dose produced 22.5% average weight loss at 72 weeks. Dosing starts at 2.5mg weekly and titrates up gradually. With a 5-day half-life, Zepbound reaches steady state after about 4 weeks at each dose level.

Standard Zepbound Dosage Chart

Tier	Weekly Dose	Duration	Pen Color
1	2.5 mg	4 weeks	Purple pen
2	5 mg	4 weeks	Brown pen
3	7.5 mg	4 weeks	Light green pen
4	10 mg	4 weeks	Dark green pen
5	12.5 mg	4 weeks	Gray pen
6	15 mg	Maintenance	Blue pen

Key Facts About Zepbound

Active Ingredient: Tirzepatide
Half-life: Approximately 5 days
FDA Approval: Chronic Weight Management (2023)
Maximum Dose: 15mg weekly
Administration: Once weekly subcutaneous injection
Mechanism: Dual GLP-1/GIP receptor agonist
Pen Options: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, 15mg (color-coded)

Zepbound vs Mounjaro

Zepbound and Mounjaro contain the same active ingredient (tirzepatide) manufactured by Eli Lilly. Zepbound is specifically approved for chronic weight management in adults with obesity or overweight with weight-related conditions. Mounjaro is approved for type 2 diabetes. The dosing schedule is identical, but they are prescribed for different indications.

Note: Individual dosing may vary. Always follow guidance from your healthcare provider.

// FAQ

Zepbound Calculator FAQ

What is the half-life of Zepbound?

Zepbound (tirzepatide) has a half-life of approximately 5 days. This means after 5 days, about 50% of the drug remains in your system. The dual GLP-1/GIP mechanism provides appetite suppression throughout the week.

How long does Zepbound stay in your system?

After stopping Zepbound, it takes approximately 5 half-lives (about 25 days) for the drug to be essentially cleared from your system. Weight management effects may continue during this washout period.

When do I reach steady state on Zepbound?

You reach steady state after approximately 4 weeks of consistent weekly dosing at the same dose level. At steady state, appetite suppression and weight loss effects become more consistent.

How long until Zepbound is out of my system?

Zepbound (tirzepatide) takes approximately 25 days to fully clear your system after your last dose. This is based on the 5-day half-life: after each 5-day period, half the remaining drug is eliminated. After 5 half-lives (25 days), less than 3% remains. Side effects typically diminish within the first 1-2 weeks after stopping.

Can I use this calculator for compounded tirzepatide?

Yes. This Zepbound calculator works for any tirzepatide formulation including compounded versions. Simply enter your dose amount and schedule. For reconstituted compounded tirzepatide, use our reconstitution calculator to determine your injection volume, then enter the mg dose here to track your levels.

Get started in seconds with our pre-built titration templates, or build your own custom schedule below.

Statistics

Peak Amount

Today's Amount

Average Stable Amount

Days until stable Click to learn how stability is calculated

Total Administered Complete Plot

Total Administered so far

Out of System (<0.02mg)

Weight Trend

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Drug Amount Plot

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Generate a schedule and click "Generate Plot" to visualize

What's a half-life?

The time your body needs to clear half a dose. After about five half-lives, a single dose is essentially gone. Tirzepatide has a half-life of roughly 5 days, so one dose takes about 25 days to clear; Semaglutide is closer to 7 days; Retatrutide is about 6 days.

Read the full half-life guide

What's steady state?

The point where what you take in each week equals what your body clears. Most weekly GLP-1s reach it after 4–5 weeks of consistent dosing — that's when blood levels stop climbing and the chart flattens out.

Read the full steady-state guide

Dose Schedule

Week	/Week	Date	Day	Time	Vial	IU	Dose (mg)	Weight (kg)	Journal	Actions

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