Weight-Based Peptide Dosing — mcg/kg Calculator

Published 2026-08-28 · Lyophile Editorial

mcg/kg Dose Calculator for Research Peptides

Enter subject weight and protocol dose to get absolute dose, volume, and syringe units instantly.

The math: Dose (mcg) = Body Weight (kg) × Protocol Dose (mcg/kg)

For an 80 kg subject at 2 mcg/kg: 80 × 2 = 160 mcg. At 2,500 mcg/mL (5 mg in 2 mL), that's 160 ÷ 2,500 = 0.064 mL = 6.4 units on a U-100 insulin syringe.

mcg/kg to Absolute Dose Table (70–100 kg)

Multiply weight by protocol dose — no unit shifting, no constants. Read your absolute dose directly from the table below.

| Body Weight (kg) | 1 mcg/kg | 2 mcg/kg | 3 mcg/kg | 5 mcg/kg | 10 mcg/kg | |---|---|---|---|---|---| | 70 | 70 mcg | 140 mcg | 210 mcg | 350 mcg | 700 mcg | | 75 | 75 mcg | 150 mcg | 225 mcg | 375 mcg | 750 mcg | | 80 | 80 mcg | 160 mcg | 240 mcg | 400 mcg | 800 mcg | | 85 | 85 mcg | 170 mcg | 255 mcg | 425 mcg | 850 mcg | | 90 | 90 mcg | 180 mcg | 270 mcg | 450 mcg | 900 mcg | | 95 | 95 mcg | 190 mcg | 285 mcg | 475 mcg | 950 mcg | | 100 | 100 mcg | 200 mcg | 300 mcg | 500 mcg | 1,000 mcg |

A 100 kg subject at 10 mcg/kg needs 1,000 mcg — a full milligram. At 2,500 mcg/mL, that's 0.4 mL = 40 units. Won't fit in a 0.3 mL syringe in one draw.

Practical check: Most mcg/kg protocols sit in the 1–10 mcg/kg range. Above 20 mcg/kg, verify the source — it may be mg/kg, a 1,000× difference.

Reconstitution Calculator: Peptide + Bacteriostatic Water

Select peptide mass and diluent volume to get concentration and mcg per U-100 unit.

The math: 5 mg = 5,000 mcg. Divide by 2 mL → 2,500 mcg/mL. A U-100 syringe has 100 units per mL, so each unit delivers 25 mcg.

| Peptide Mass | Diluent Volume | Concentration (mcg/mL) | mcg per U-100 unit | |---|---|---|---| | 5 mg | 1 mL | 5,000 | 50 | | 5 mg | 2 mL | 2,500 | 25 | | 5 mg | 3 mL | 1,667 | 16.7 | | 10 mg | 2 mL | 5,000 | 50 | | 10 mg | 3 mL | 3,333 | 33.3 | | 10 mg | 4 mL | 2,500 | 25 |

Why 2 mL for a 5 mg vial: 2,500 mcg/mL puts a 200 mcg dose at 8 units — readable on any insulin syringe. At 1 mL, that same dose is 4 units — less forgiving. At 3 mL, odd doses like 225 mcg land at 13.5 units — half-unit estimating.

Failure mode: 10 mg in 1 mL = 10,000 mcg/mL = 100 mcg per unit. A 150 mcg dose is 1.5 units. A half-unit error is a 33% dose error. Use more diluent for small doses.

Syringe Volume Calculator

Enter dose and concentration to get recommended syringe size and draw volume.

Rule: Keep dose volume between 20–80% of barrel capacity. For most 70–100 kg mcg/kg protocols, a 0.5 mL (50 unit) syringe covers the range; use 1 mL for doses above 400 mcg.

| Dose (mcg) at 2,500 mcg/mL | Volume (mL) | U-100 units | Recommended syringe | |---|---|---|---| | 50 | 0.02 | 2 | 0.3 mL | | 100 | 0.04 | 4 | 0.3 mL | | 150 | 0.06 | 6 | 0.3 mL | | 200 | 0.08 | 8 | 0.3 mL | | 300 | 0.12 | 12 | 0.5 mL | | 500 | 0.20 | 20 | 0.5 mL | | 750 | 0.30 | 30 | 0.5 mL or 1 mL | | 1,000 | 0.40 | 40 | 1 mL |

Dead-space problem: Standard insulin syringes hold 2–4 units of residual liquid in the needle hub after full depression. Fine for a 20-unit dose (10–20% loss), catastrophic for a 2-unit dose (100–200% loss). Low dead-space syringes reduce this to under 1 unit. For doses under 5 units, use low dead-space or accept the variance.

Draw Volume Calculator

Enter dose and concentration to get mL and U-100 units.

Worked example — 225 mcg at 2,500 mcg/mL:

Concentration: 5 mg peptide + 2 mL diluent = 2,500 mcg/mL.
Dose: 225 mcg (75 kg × 3 mcg/kg).
Divide: 225 ÷ 2,500 = 0.09 mL.
Convert: 0.09 mL × 100 = 9 units on a U-100 syringe.

Second example: 10 mg vial, 3 mL diluent → 3,333 mcg/mL. Dose 500 mcg. 500 ÷ 3,333 = 0.15 mL = 15 units.

Mental math shortcut: At 2,500 mcg/mL, every unit = 25 mcg. A 200 mcg dose = 200 ÷ 25 = 8 units. Concentration per unit is always (total mcg ÷ total mL) ÷ 100.

Accuracy note: Standard syringes mark whole units only. 0.3 mL and 0.5 mL syringes have 1-unit graduations; 1 mL syringes typically have 2-unit graduations. Fractional units require rounding — or dilute further.

Bacteriostatic Water Sources

Bacteriostatic water is 0.9% benzyl alcohol in water for injection, per USP monograph. Stable for 28 days after first puncture when stored per manufacturer guidance. Choose suppliers with clear lot tracking and sterile packaging.

BAC Water Depot — sterile 0.9% benzyl alcohol water, multiple vial sizes, lot-numbered
Hospira — USP-grade bacteriostatic water, standard in clinical supply chains
Covidien — pharmaceutical-grade, commonly stocked by medical distributors

Research Peptide Sources

Research peptides are for laboratory use only — not for human or animal administration. Verify certificates of analysis with HPLC purity data and mass spectrometry confirmation.

Alpha Amino USA — per-lot HPLC/MS COA, US-shipped, research-use labeled
Peptide Sciences — third-party tested, published COAs, research-grade catalog
PureRawz — research peptide catalog, COA available per lot, US-based shipping

For research use only — not clinical guidance. Always verify your concentration math before drawing. A 10× error in reconstitution volume produces a 10× error in delivered dose.

Frequently asked questions

How do I calculate the absolute dose from a mcg/kg protocol?

Multiply the subject's body weight in kilograms by the protocol dose in mcg/kg. For example, an 80 kg subject at 2 mcg/kg requires 160 mcg. This direct multiplication yields the absolute dose without any unit shifting or additional constants, as stated in the article's core formula.

What is the concentration when 5 mg of peptide is mixed with 2 mL of bacteriostatic water?

Reconstituting 5 mg (5,000 mcg) of peptide with 2 mL of diluent yields a concentration of 2,500 mcg/mL. On a U-100 insulin syringe, each unit delivers 25 mcg, making a 200 mcg dose equal to 8 units, as shown in the article's reconstitution table.

What syringe size is recommended for a 1,000 mcg dose at 2,500 mcg/mL?

A 1,000 mcg dose at 2,500 mcg/mL requires 0.4 mL, or 40 units on a U-100 syringe. The article's syringe volume table recommends a 1 mL syringe for this dose, as it exceeds the 0.5 mL barrel's optimal 20–80% fill range.

Why is 2 mL of diluent recommended for a 5 mg peptide vial?

Using 2 mL for a 5 mg vial creates a 2,500 mcg/mL concentration, placing a 200 mcg dose at 8 units on a U-100 syringe. This volume is more readable than 4 units at 1 mL and avoids half-unit estimating required at 3 mL, per the article's reconstitution guidance.