GLP-1 Reconstitution & Dose Calculator: Semaglutide & Tirzepatide

Enter your vial size, BAC water, and weekly dose, get the exact mL and insulin syringe units for compounded semaglutide, tirzepatide, or retatrutide.

Last updated August 2026 · Reviewed by the Regimen Team

Peptide reconstitution

Peptide Reconstitution Calculator

Calculate your exact dose

Enter your vial details to calculate how many units to draw for your dose.

Peptide Amount (mg)

Bacteriostatic Water (mL)

Desired Dose

Common doses: Semaglutide (0.25-2.4mg), Tirzepatide (2.5-15mg)

This calculator is for informational purposes only, so always double-check your result with a healthcare provider. Compounded medications should only be obtained from licensed compounding pharmacies. We assume no liability for dosing errors.

How to use it

How to Use This Calculator

01

Enter vial size

The mg amount on your GLP-1 vial (e.g., 5mg, 10mg)
02

Enter BAC water

How much bacteriostatic water you added (typically 2mL)
03

Enter weekly dose

Your target dose in mg (e.g., 0.25mg, 0.5mg, 2.5mg)
04

Read your result

See exactly how many units to draw on your syringe

How to Calculate Your GLP-1 Injection Dose

If you’re using compounded semaglutide or tirzepatide (not pre-filled pens like Ozempic or Mounjaro), you need to calculate how many units to draw on your insulin syringe based on your vial’s concentration and your prescribed dose.

The formula:

Units to draw = Prescribed dose (mg) ÷ Concentration (mg/mL) x 100

Example: Your compounded semaglutide is 5mg/2mL (2.5mg/mL). Your prescribed dose is 0.25mg.

0.25 ÷ 2.5 x 100 = 10 units

Semaglutide Titration Schedule

Semaglutide is typically titrated (gradually increased) to reduce side effects. Here’s the standard titration:

Week	Weekly Dose	Purpose
Weeks 1-4	0.25mg	Starting dose, let your body adjust
Weeks 5-8	0.5mg	First increase
Weeks 9-12	1.0mg	Second increase
Weeks 13-16	1.7mg	Third increase (Wegovy protocol)
Week 17+	2.4mg	Maintenance dose (Wegovy protocol)

Your provider may adjust this schedule based on your response and tolerance. Use the calculator above to recalculate your syringe units at each dose increase. Regimen’s GLP-1 titration planner maps out your full titration schedule with dates.

Tirzepatide Titration Schedule

Week	Weekly Dose	Purpose
Weeks 1-4	2.5mg	Starting dose
Weeks 5-8	5mg	First increase
Weeks 9-12	7.5mg	Second increase
Weeks 13-16	10mg	Third increase
Weeks 17-20	12.5mg	Fourth increase
Week 21+	15mg	Maximum dose

Titrate only when your provider recommends it. Not everyone reaches the maximum dose.

Track Your GLP-1 Progress

Calculating your dose is step one. Tracking whether it’s working is step two.

Log every injection in Regimen - dose, timing, and injection site.
Track your weight and body fat automatically through Apple Health or Google Health Connect.
Monitor side effects over time - see if nausea decreases as your body adjusts to each dose level.
Visualize your medication levels between weekly injections with Regimen’s half-life visualizer.

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Example GLP-1 Calculations

Common dosing scenarios for compounded semaglutide and tirzepatide

	Vial	Water	Weekly dose
Semaglutide	5mg	2mL	0.5mg	20 units	10 weeks per vial
Tirzepatide	10mg	2mL	2.5mg	50 units	4 weeks per vial
Semaglutide	10mg	3mL	1mg	30 units	10 weeks per vial

What This GLP-1 Calculator Does

This calculator is designed for compounded versions of GLP-1 receptor agonists - the kind that come as lyophilized powder in vials rather than pre-filled pens. If you’re using compounded semaglutide (the active ingredient in Ozempic and Wegovy) or compounded tirzepatide (Mounjaro and Zepbound), you need to reconstitute the powder with bacteriostatic water before injecting.

Enter your vial size, how much BAC water you added, and your prescribed dose. The calculator converts your dose into exact insulin syringe units so you draw the right amount every time. It also works for retatrutide and other emerging GLP-1 compounds.

Semaglutide reconstitution calculator

For compounded semaglutide, the most common vials are 2 mg, 5 mg, and 10 mg. The 5 mg vial reconstituted with 2 mL of BAC water gives a clean 2.5 mg/mL concentration that maps neatly to every standard titration step (0.25 mg = 10 units, 0.5 mg = 20 units, 1.0 mg = 40 units, 2.4 mg = 96 units on a 100-unit insulin syringe). Larger 10 mg vials in 2 mL or 3 mL are common for maintenance doses.

Tirzepatide reconstitution calculator

Compounded tirzepatide ships in larger vials - typically 10 mg, 15 mg, 30 mg, and 60 mg. A 30 mg vial in 1.5 mL gives 20 mg/mL, where 2.5 mg = 12.5 units and 15 mg = 75 units. Enter your specific vial size and BAC water volume above to skip the math.

On a brand KwikPen there is no vial math at all, since each pen delivers one preset weekly dose. See all six Mounjaro doses and where each one sits in the titration schedule.

Need help building a dose escalation timeline? Learn more in our GLP-1 tracker guide

GLP-1 Titration Planner

Get a personalized dose escalation schedule with exact dates

Tirzepatide-specific reconstitution calculator

Vial size and BAC water to insulin units, with a draw-to-here syringe diagram

Retatrutide-specific reconstitution calculator

5-30mg vial presets, U-100 syringe selector, and a draw-to-here syringe diagram

Peptide Calculator

Calculate doses for BPC-157, TB-500, and other peptides

Data Sources

This tool uses dosing information from official prescribing information:

Reconstitution Math - Standard concentration and volume calculations for peptide reconstitution
GLP-1 Dosing Guidelines - Typical titration schedules for semaglutide and tirzepatide
Insulin Syringe Standards - U-100 syringe conversion: 100 units = 1mL

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Questions

GLP-1 Dosing Questions

How do I calculate my compounded semaglutide injection volume?

Divide your target dose in mg by your vial concentration in mg/mL. For example: 0.25mg dose ÷ 5mg/mL concentration = 0.05mL. Enter your vial concentration and target weekly dose into the GLP-1 dose calculator to get the exact injection volume. Always confirm your vial's concentration on the pharmacy label before calculating.

What concentration is compounded semaglutide?

Compounded semaglutide vials vary by pharmacy. Common concentrations are 2.5mg/mL, 5mg/mL, and 10mg/mL. Higher concentrations mean smaller injection volumes for the same dose. Always check your pharmacy label - entering the wrong concentration gives you the wrong dose.

How do I calculate my tirzepatide dose volume?

Tirzepatide (Mounjaro/Zepbound) dosing follows the same calculation: Volume = Dose ÷ Concentration. The standard starting dose is 2.5mg per week. If your vial is 10mg/mL, that is 0.25mL per injection. The GLP-1 calculator supports tirzepatide at any concentration.

What is the starting dose for compounded semaglutide?

The standard starting dose for semaglutide is 0.25mg per week for the first 4 weeks, matching Ozempic's approved titration schedule. After 4 weeks, most protocols increase to 0.5mg/week, then titrate upward based on tolerability and response. Your prescriber sets the schedule; the GLP-1 calculator tells you how much to draw at each dose.

How is compounded GLP-1 different from brand-name Ozempic or Mounjaro pens?

Compounded GLP-1 medications contain the same active ingredient (semaglutide or tirzepatide) but are prepared by compounding pharmacies in multi-dose vials rather than pre-filled injection pens. You draw your dose from the vial using an insulin syringe, which requires calculating the exact volume - which is what this calculator is for.

How do I calculate my compounded semaglutide dose?

Enter your vial concentration (mg/mL) and prescribed dose (mg) in the calculator above. It converts your dose into insulin syringe units. Example: for 2.5mg/mL compounded semaglutide at a 0.5mg dose, draw 20 units.

How do I calculate tirzepatide injection dose?

Same process - enter your vial concentration and prescribed dose. Compounded tirzepatide concentrations vary by pharmacy, so always check your vial label. Common concentrations include 5mg/mL and 10mg/mL.

What's the difference between compounded and brand-name GLP-1 medications?

Brand-name (Ozempic, Wegovy, Mounjaro, Zepbound) comes in pre-filled pens with preset doses - no calculation needed. Compounded semaglutide and tirzepatide comes in multi-dose vials that require you to draw your own dose with an insulin syringe. This calculator is for the compounded vial form.

How do I know when to increase my GLP-1 dose?

Follow your provider's titration schedule. Standard protocols increase every 4 weeks. Use Regimen's GLP-1 titration planner to map out your full schedule with dates, and recalculate your syringe units at each new dose.

Can I track my GLP-1 weight loss progress with Regimen?

Yes. Regimen syncs weight and body fat data from Apple Health or Google Health Connect and plots it alongside your GLP-1 injection timeline. You can see exactly how your medication correlates to your weight loss trajectory. Free for one compound, plus a two-week trial.