From MG to IU: The Retatrutide Conversion Formula for Any Vial Concentration

Calculating your peptide dosage can feel like solving a puzzle. You have a prescription for a specific milligram (mg) amount, but your syringe is marked in units (IU), and your vial’s concentration varies depending on how much bacteriostatic water you added. This confusion often leads to hesitation or, worse, incorrect dosing.

A reliable retatrutide dosing calculator simplifies this process, but understanding the underlying math ensures you are in full control of your protocol. This step-by-step guide will teach you the universal formula to convert milligrams to units, regardless of whether your vial is 5mg, 10mg, or 15mg.

This article is part of our comprehensive retatrutide dosage calculator guide.

By the end of this article, you will be able to confidently prepare your injection without relying on external tools.

What You Need Before You Start

Before performing the calculation, gather the following three pieces of information. You can usually find these on your vial label or your prescription instructions.

1. The Total Milligrams (mg) in the Vial: This is the total peptide powder amount (e.g., 5mg, 10mg, 12mg, or 15mg).
2. The Amount of Bacteriostatic Water (mL): This is the liquid you add to the vial. Common amounts are 1mL, 2mL, or 3mL.
3. Your Prescribed Dose in Milligrams (mg): This is the amount of Retatrutide you intend to take per injection.

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Note: For this guide, we assume you are using an insulin syringe, where 100 units (IU) = 1mL.

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The Universal Retatrutide Dosing Formula

To calculate your injection volume, we first need to determine the Concentration of your solution (how much peptide is in a single drop of liquid).

Step 1: Calculate Concentration (mg per mL)

Divide the total milligrams of peptide by the total milliliters of water added.

$$ \text{Concentration} = \frac{\text{Total Peptide (mg)}}{\text{Total Water (mL)}} $$

Result: This tells you how many milligrams of Retatrutide are in one milliliter of liquid.

Step 2: Calculate Units per Milligram

We need to know how many units of the syringe equal one milligram of the medication. Since 1mL = 100 units, we use this formula:

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$$ \text{Units per mg} = \frac{100 \text{ units}}{\text{Concentration (mg/mL)}} $$

Step 3: Calculate Your Final Injection Dose

Multiply your prescribed dose by the "Units per mg" value found in Step 2.

$$ \text{Final Dose (Units)} = \text{Prescribed Dose (mg)} \times \text{Units per mg} $$

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Practical Examples: Applying the Formula

Let’s look at three common scenarios to see how this works in practice.

Scenario A: The Standard 5mg Vial

You have a 5mg vial and add 2mL of bacteriostatic water. Your prescribed dose is 2mg.

1. Calculate Concentration:
   $$ 5\text{mg} / 2\text{mL} = 2.5\text{mg/mL} $$
2. Calculate Units per mg:
   $$ 100\text{ units} / 2.5\text{mg} = 40\text{ units per mg} $$
3. Calculate Final Dose:
   $$ 2\text{mg (prescribed)} \times 40 = \mathbf{80\text{ units}} $$

You will draw up to the 80-unit mark on your syringe.

Scenario B: The Concentrated 10mg Vial

You have a 10mg vial and add 1mL of bacteriostatic water. Your prescribed dose is 2mg.

1. Calculate Concentration:
   $$ 10\text{mg} / 1\text{mL} = 10\text{mg/mL} $$
2. Calculate Units per mg:
   $$ 100\text{ units} / 10\text{mg} = 10\text{ units per mg} $$
3. Calculate Final Dose:
   $$ 2\text{mg (prescribed)} \times 10 = \mathbf{20\text{ units}} $$

You will draw up to the 20-unit mark on your syringe.

Scenario C: The Large 15mg Vial

You have a 15mg vial and add 3mL of bacteriostatic water. Your prescribed dose is 4.5mg.

1. Calculate Concentration:
   $$ 15\text{mg} / 3\text{mL} = 5\text{mg/mL} $$
2. Calculate Units per mg:
   $$ 100\text{ units} / 5\text{mg} = 20\text{ units per mg} $$
3. Calculate Final Dose:
   $$ 4.5\text{mg (prescribed)} \times 20 = \mathbf{90\text{ units}} $$

You will draw up to the 90-unit mark on your syringe.

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Actionable Takeaways

• The "Divide by 5" Shortcut: If you add 2mL of water to any vial size, simply divide the total mg by 2 to get your concentration. Then, divide 100 by that number to find your units per mg.
• Double-Check Your Water: If you accidentally add too much or too little water, the concentration changes. Always recalculate your dose if the water volume differs from your plan.
• Micro-Dosing Adjustments: If you are on a low starting dose (e.g., 0.5mg), the calculation remains the same; just ensure your syringe is a 100-unit (1mL) syringe to accurately measure small amounts like 10 or 20 units.
• Safety First: Never guess your dose. If the math seems confusing, write it down or use a verified retatrutide dosing calculator tool to verify your manual calculation before drawing up the medication.