How to Calculate Your Peptide Dosage: Weight-Based Guide

Key Takeaways

• Most peptides are dosed in micrograms per kilogram (mcg/kg) — Your body weight directly determines your optimal dose for many peptides.
• Start low, titrate up — Begin at the lower end of the recommended range and increase gradually based on response and side effects.
• Reconstitution math matters — Understanding concentration after reconstitution is essential for drawing accurate doses from a vial.
• Timing and frequency affect results — The same total daily dose can produce different effects depending on when and how often you administer it.
• Use a calculator — Visit peptideplaybook.health/tools to automatically calculate your personalized dose based on weight and peptide choice.

Why Accurate Dosing Matters

Peptide dosing isn't like taking a multivitamin where "close enough" works fine. These are bioactive compounds that interact with specific receptors in your body, and the dose-response relationship is often non-linear. Too little and you won't see results. Too much and you increase side effects without proportional benefits — or worse, you can trigger receptor desensitization where your body stops responding to the peptide altogether.

The difference between an effective dose and a wasteful one can be as small as 50 micrograms. That's why understanding dosing principles, doing the math correctly, and measuring precisely are foundational skills for anyone using peptides.

This guide will teach you the core concepts behind peptide dosing, walk you through the math step by step, and give you practical frameworks for the most popular peptides. No advanced math degree required — just basic arithmetic and a willingness to be precise.

Understanding Peptide Dosing Units

Before diving into calculations, let's clarify the units you'll encounter:

Micrograms (mcg or μg)

The standard unit for peptide dosing. One microgram is one-millionth of a gram (1/1,000,000 g) or one-thousandth of a milligram (1/1,000 mg). Most peptide doses fall in the range of 100–2,000 mcg per administration.

Milligrams (mg)

Peptide vials are typically labeled in milligrams. A common vial size is 5 mg, meaning the vial contains 5,000 mcg of peptide. Some peptides like semaglutide are dosed in milligrams rather than micrograms because effective doses are in the mg range.

International Units (IU)

Some peptides — particularly HGH and HCG — are measured in International Units rather than weight-based units. IU is a standardized measure of biological activity. The conversion between IU and milligrams varies by compound.

Micrograms per Kilogram (mcg/kg)

The gold standard for individualized dosing. This approach scales the dose to your body weight, accounting for the fact that a 60 kg person and a 100 kg person have very different physiology. Research protocols typically report doses in mcg/kg to enable accurate replication across different body sizes.

The Weight-Based Dosing Principle

Weight-based dosing is simple in concept: multiply a per-kilogram dose by your body weight to get your total dose.

Formula: Total Dose (mcg) = Dose per kg (mcg/kg) × Body Weight (kg)

For example, if a peptide is recommended at 1 mcg/kg and you weigh 80 kg:

Total Dose = 1 mcg/kg × 80 kg = 80 mcg per administration

Converting Pounds to Kilograms

If you know your weight in pounds, divide by 2.205 to get kilograms:

• 150 lbs ÷ 2.205 = 68 kg
• 180 lbs ÷ 2.205 = 81.6 kg
• 200 lbs ÷ 2.205 = 90.7 kg
• 220 lbs ÷ 2.205 = 99.8 kg

Or use a simpler approximation: divide your weight in pounds by 2.2. Close enough for peptide dosing purposes.

When Weight-Based Dosing Applies

Not every peptide uses strict weight-based dosing. Some have flat dose recommendations (e.g., "take 250 mcg" regardless of body weight). However, even with flat-dose peptides, your body weight influences the effective concentration in your system. Heavier individuals may need doses at the higher end of the recommended range, and lighter individuals may do well at the lower end.

Here's a general framework:

• Strict mcg/kg dosing: Research peptides where clinical trials used weight-based protocols (e.g., some GH secretagogues, AOD-9604).
• Range-based dosing: Peptides with a recommended range (e.g., CJC-1295 at 100–300 mcg). Your body weight helps you choose where in the range to start.
• Fixed dosing: Some peptides like semaglutide use standardized dose escalation schedules regardless of weight (0.25 mg → 0.5 mg → 1.0 mg, etc.).

Reconstitution Math: From Vial to Syringe

Once you know your target dose in micrograms, you need to figure out how much liquid to draw from your reconstituted vial. This is where most dosing errors happen, so pay close attention.

Step 1: Know Your Vial Content

Check the vial label for the total peptide content. Common sizes:

• 2 mg vial = 2,000 mcg
• 5 mg vial = 5,000 mcg
• 10 mg vial = 10,000 mcg

Step 2: Choose Your Reconstitution Volume

You'll add bacteriostatic water (BAC water) to the lyophilized peptide powder. The amount of water you add determines the concentration. Common reconstitution volumes:

• 1 mL (most concentrated — for small doses)
• 2 mL (standard for most protocols)
• 3 mL (more dilute — easier to measure small doses)
• 5 mL (very dilute — useful for very small or precise doses)

Step 3: Calculate Concentration

Formula: Concentration (mcg per unit) = Total Peptide (mcg) ÷ Total Units on Syringe

An insulin syringe is marked in "units" where 100 units = 1 mL. So:

• 5,000 mcg peptide + 2 mL BAC water = 5,000 mcg in 200 units = 25 mcg per unit
• 5,000 mcg peptide + 1 mL BAC water = 5,000 mcg in 100 units = 50 mcg per unit
• 10,000 mcg peptide + 2 mL BAC water = 10,000 mcg in 200 units = 50 mcg per unit

Step 4: Calculate Units to Draw

Formula: Units to Draw = Desired Dose (mcg) ÷ Concentration (mcg per unit)

Example: You want 200 mcg from a 5 mg vial reconstituted with 2 mL BAC water:

• Concentration = 5,000 mcg ÷ 200 units = 25 mcg/unit
• Units to draw = 200 mcg ÷ 25 mcg/unit = 8 units on the insulin syringe

Always double-check your math before drawing. A common mistake is confusing mg and mcg, which results in a 1,000x dosing error. Write down your calculations and keep them with your supplies.

For instant calculations, use our peptide dosage calculator — enter your vial size, reconstitution volume, and desired dose, and it tells you exactly how many units to draw.

Dosing Guidelines for Popular Peptides

Here are evidence-based dosing ranges for commonly used peptides. Always start at the lower end and titrate up based on your response.

CJC-1295 (no DAC) / Ipamorelin

• Dose: 100–300 mcg of each peptide per administration
• Frequency: 1–3 times daily
• Timing: Before bed (primary dose), optional morning and post-workout doses
• Weight consideration: Lighter individuals (under 70 kg) start at 100 mcg; heavier individuals (over 90 kg) may use 200–300 mcg
• Notes: Administer on an empty stomach (no food for 1–2 hours before and 30 minutes after). GH release is blunted by elevated blood sugar and insulin.

BPC-157

• Dose: 250–500 mcg per administration
• Frequency: 1–2 times daily
• Timing: Morning and evening, or as close to the injury site as possible for injectable use
• Weight consideration: Research often uses ~10 mcg/kg. An 80 kg person would calculate 800 mcg/day, split into two 400 mcg doses.
• Notes: Can be administered subcutaneously near the injury or orally for systemic and gut benefits.

Semaglutide

• Dose: Standard escalation — 0.25 mg/week (weeks 1–4) → 0.5 mg/week (weeks 5–8) → 1.0 mg/week (weeks 9–12) → up to 2.4 mg/week
• Frequency: Once weekly
• Weight consideration: Fixed dose escalation, not weight-based. However, higher body weight may require progression to the higher end of dosing for full effect.
• Notes: Slow titration is essential to minimize GI side effects (nausea, etc.). Don't rush the escalation.

MK-677 (Ibutamoren)

• Dose: 10–25 mg daily (oral)
• Frequency: Once daily
• Timing: Evening or before bed to align with natural GH pulse
• Weight consideration: Start at 10 mg regardless of weight. Increase to 25 mg only if well-tolerated and IGF-1 levels remain in range.
• Notes: Monitor fasting glucose closely. MK-677 can significantly impact blood sugar in sensitive individuals.

TB-500 (Thymosin Beta-4)

• Dose: Loading phase: 750–2,000 mcg twice weekly for 4–6 weeks. Maintenance: 750 mcg once or twice weekly.
• Frequency: 2x/week (loading), 1–2x/week (maintenance)
• Weight consideration: Heavier individuals generally use the higher end of loading doses.
• Notes: Often stacked with BPC-157 for synergistic healing effects.

Timing and Frequency Principles

When and how often you dose affects results as much as the dose itself: