How to Calculate Your Peptide Dose: From Vial to Syringe Units

The Core Formulas

Step 1: Calculate Vial Concentration

Concentration (mcg/mL) = Vial weight (mg) × 1000 ÷ Water volume (mL)

Step 2: Convert Target Dose to Syringe Units

Units (on 100U syringe) = (Target dose in mcg ÷ Concentration in mcg/mL) × 100

Step 3: For 50U Syringes

Units (on 50U syringe) = (Target dose in mcg ÷ Concentration in mcg/mL) × 50

These formulas let you move seamlessly from vial specifications to the exact syringe marking.

Worked Example 1: BPC-157

Given:

Step 1: Calculate concentration

Concentration = (5 mg × 1000) ÷ 5 mL = 5000 mcg ÷ 5 mL = 1000 mcg/mL

Step 2: Convert to syringe units

Units = (250 mcg ÷ 1000 mcg/mL) × 100 = 0.25 × 100 = 25 units

Result: Draw to the 25-unit mark on your 100U syringe.

Worked Example 2: TB-500

Given:

Step 1: Calculate concentration

Concentration = (2 mg × 1000) ÷ 1 mL = 2000 mcg ÷ 1 mL = 2000 mcg/mL

Step 2: Convert to syringe units

Units = (2000 mcg ÷ 2000 mcg/mL) × 100 = 1 × 100 = 100 units

Result: Draw to the 100-unit mark—the full syringe capacity.

Note: If your protocol requires 5 mg and your vial is 2 mg, you'd need 250 units (exceeds one syringe). You'd either split into two injections or use a 300U syringe.

Worked Example 3: Semaglutide (Step-Up Protocol)

Given:

Step 1: Calculate concentration

Concentration = (10 mg × 1000) ÷ 1 mL = 10,000 mcg/mL

Week 1 (0.25 mg = 250 mcg):

Units = (250 mcg ÷ 10,000 mcg/mL) × 100 = 0.025 × 100 = 2.5 units

Week 2 (0.5 mg = 500 mcg):

Units = (500 mcg ÷ 10,000 mcg/mL) × 100 = 0.05 × 100 = 5 units

Week 3 (0.75 mg = 750 mcg):

Units = (750 mcg ÷ 10,000 mcg/mL) × 100 = 0.075 × 100 = 7.5 units

Result: For small doses like these, a 50U syringe gives better readability (you'd draw 1.25 units, 2.5 units, and 3.75 units respectively on a 50U syringe, making the marks larger and easier to see).

Understanding Concentration Notation

You might see concentration written as:

Always convert milligrams to micrograms (multiply by 1000) before calculating your dose.

The Importance of Accuracy

A calculation error of just 10% doubles or halves your dose, affecting safety and results. Always:

Using MyProtocolStack for Calculations

MyProtocolStack has a built-in peptide dose calculator. Enter your vial specifications and target dose, and the platform calculates the exact syringe marking automatically. This eliminates math errors and stores your calculations for future reference.

Advanced: Adjusting for Concentration Changes

If you reconstitute the same peptide vial with different water volumes, your concentration changes. Always recalculate your dose:

Same 5 mg BPC-157 vial, but reconstituted with 10 mL instead of 5 mL:

Concentration = (5 mg × 1000) ÷ 10 mL = 500 mcg/mL (half the previous concentration)

For a 250 mcg dose: Units = (250 ÷ 500) × 100 = 50 units (double the previous marking)

This is why tracking your exact reconstitution details is essential.

This article is for informational and educational purposes only and does not constitute medical advice. Always consult a licensed healthcare provider before starting, adjusting, or stopping any peptide protocol. MyProtocolStack is a protocol tracking and blood work analysis platform — it is not a medical device and does not provide clinical recommendations.