Dose Tracking Calculator

GLP-1 & Retatrutide (GLP-3) Calculator & Dosage Chart

See exactly when your medication reaches full strength and plan your doses with confidence. Know your peak medication levels, optimize your injection timing, and track your titration progress, all in one place.

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Quick Access: Reconstitution Calculator | Retatrutide Dosing Guide | microdosing retatrutide guide

Drug Amount Plot
Retatrutide • 12 weeks
7 Days 30 Days 90 Days
2.0mg 1.5mg 1.0mg 0.5mg Today Dec 1 Dec 15 Jan 1 Jan 8
Jan 8, 2026
1.85mg ↑ 12%
● Peak: 2.1mg ● Avg: 1.65mg
Steady state in 3 days
3 research compounds
120-168 hr half-life modeling
Built on clinical trial data
// Half-Life Science and why it matters

How GLP-1 Half-Life Calculations Work

Understanding medication half-life helps you predict drug levels, optimize dosing timing, and know when you'll reach steady state. Our calculator uses exponential decay formulas based on published clinical trial data.

This matters because titrating up gets tricky with half-lives this long. It's easy to lose track of how much is actually in your system, especially when dosing multiple times per week. For example, if you take 2mg of Retatrutide and don't feel much, you might bump up to 3mg the following week, but there's still approximately 1mg left from your previous dose. So now you have 4mg in your body, not 3mg. This compounds week after week. GLP3 Planner helps you visualize the total amount in your system and track how you feel, so you can make informed titration decisions.

Retatrutide
~6 days
144 hours half-life

Triple agonist (GLP-1/GIP/Glucagon). Steady state reached in 4-5 weeks of weekly dosing.

Tirzepatide
~5 days
120 hours half-life

Dual agonist (GLP-1/GIP). Available as Mounjaro and Zepbound. Steady state in ~4 weeks.

Semaglutide
~7 days
168 hours half-life

GLP-1 agonist. Available as Ozempic and Wegovy. Steady state in 4-5 weeks.

Steady-state is typically reached after 4-5 half-lives of consistent dosing. This is when peak and trough concentrations stabilize at predictable levels.

// Standard Titration

GLP-1 Dosing Schedules

Retatrutide Titration

Standard weekly escalation protocol

  • 2mg Weeks 1-4
  • 4mg Weeks 5-8
  • 6mg Weeks 9-12
  • 8mg Weeks 13-16
  • 12mg Maintenance
  •  
Retatrutide standard titration →
Retatrutide microdosing guide →
Retatrutide calculator →
Retatrutide reconstitution calculator →
Retatrutide side effects →

Tirzepatide (Mounjaro/Zepbound)

FDA-approved escalation schedule

  • 2.5mg Weeks 1-4
  • 5mg Weeks 5-8
  • 7.5mg Weeks 9-12
  • 10mg Weeks 13-16
  • 12.5mg Weeks 17-20
  • 15mg Maintenance
Tirzepatide standard titration →
Tirzepatide microdosing guide →
Tirzepatide calculator →
Tirzepatide reconstitution calculator →
Tirzepatide side effects →

Semaglutide (Ozempic/Wegovy)

Standard escalation for weight management

  • 0.25mg Weeks 1-4
  • 0.5mg Weeks 5-8
  • 1mg Weeks 9-12
  • 1.7mg Weeks 13-16
  • 2.4mg Maintenance (Wegovy)
  •  
Semaglutide standard titration →
Semaglutide microdosing guide →
Semaglutide calculator →
Semaglutide reconstitution calculator →
Semaglutide side effects →
// Features

Built for precision

01

Pharmacokinetic Modeling

Our GLP-1 half-life calculator uses two-compartment pharmacokinetic models based on published clinical research data. Understand exactly how retatrutide, tirzepatide, and semaglutide behave in your body over time. The calculator factors in absorption rates, distribution volumes, and elimination half-lives specific to each compound.

Learn about PK modeling →
02

Visual Drug Concentration Tracking

Interactive charts show your medication journey from first dose to steady state. Visualize peak concentrations after each injection, trough levels before your next dose, and the gradual accumulation over weeks. Perfect for understanding why GLP-1 medications take 4-5 weeks to reach full effect.

Use the full calculator →
03

Flexible Dosing Schedules

Create custom dosing schedules with tiered escalation protocols for any GLP-1 medication. Plan your titration strategy from starting dose through maintenance phase. Supports both standard weekly dosing and microdosing protocols. Save multiple schedules to compare different approaches.

Retatrutide dosing guide →
// Supported

Research Compounds

Retatrutide Tirzepatide Semaglutide Ozempic Wegovy Mounjaro Zepbound
// FAQ

Common questions

Do I need an account?
No account required to use the calculator. Creating an account lets you save schedules, track your weight progress, and share dosing plans with your healthcare provider.
Is this medical advice?
No. GLP3 Planner is an educational tool for visualizing pharmacokinetics. Always consult your healthcare provider before making any changes to your medication regimen.
What happens if I miss a dose?
If you miss a dose, take it as soon as you remember, as long as your next scheduled dose is at least 3 days away. If it's closer than that, skip the missed dose and resume your regular schedule. Don't double up to make up for a missed dose. GLP-1 medications have long half-lives, so a single missed dose won't dramatically affect your overall levels, but try to stay consistent for best results.
Do I need to cycle retatrutide? Or can I keep taking it the whole year?
Based on current clinical data, retatrutide does not require cycling. Phase 2 trials ran for 48 weeks with continued efficacy and no evidence of tolerance buildup. Most GLP-1 agonists are designed for long-term use. However, FDA approval and long-term safety data (beyond 48 weeks) are still pending. Consult your healthcare provider about your specific treatment duration.
How do I calculate my retatrutide dose?
Use our retatrutide calculator to model your dosing schedule. Enter your starting dose and escalation plan, and the calculator will show drug concentration levels over time. Retatrutide has a ~6 day half-life, meaning it takes about 4-5 weeks to reach steady state at each dose tier.
What is the half-life of tirzepatide?
Tirzepatide (sold as Mounjaro and Zepbound) has an elimination half-life of approximately 5 days (120 hours). This means half the drug is eliminated from your system every 5 days. The long half-life allows for convenient once-weekly dosing and means tirzepatide reaches steady state after about 4 weeks of consistent dosing.
How long does semaglutide stay in your system?
Semaglutide (Ozempic/Wegovy) has a half-life of approximately 7 days (168 hours). After stopping the medication, it takes about 5 half-lives (35 days) for semaglutide to be effectively eliminated from your system. This long half-life is why side effects may persist for several weeks after discontinuation.
Can I use this calculator for compounded tirzepatide?
Yes, the pharmacokinetic calculations work for both brand-name and compounded tirzepatide since the active molecule is identical. Our reconstitution calculator can also help you calculate BAC water volumes for reconstituting lyophilized peptides.
What is steady-state and why does it matter?
Steady-state occurs when the amount of drug entering your system equals the amount being eliminated. For weekly GLP-1 medications, this happens after 4-5 half-lives of consistent dosing. At steady-state, drug levels stabilize with predictable peaks and troughs. This is why titration schedules keep you at each dose for 4 weeks before escalating.
How accurate are the calculations?
Our calculations use published half-life data from clinical trials. While individual pharmacokinetics may vary based on body weight and metabolism, the models provide a reliable approximation of drug concentration over time.

Disclaimer: GLP3 Planner is for educational purposes only and does not provide medical advice. Consult your healthcare provider before making any changes to your medication regimen.