Overview
Accurate dose calculation is fundamental to reproducible peptide research. Errors in concentration math lead to under- or over-dosing in animal models, which compromises experimental validity and wastes expensive research compounds. This reference covers the core calculations used in peptide research protocols.
Core Formula
The fundamental equation for determining injection volume:
Volume to inject (mL) = Desired dose (mg) ÷ Reconstituted concentration (mg/mL)
In research, doses are typically expressed in micrograms (µg), so the formula becomes:
Volume to inject (µL) = Desired dose (µg) ÷ Concentration (µg/mL)
Step-by-Step Example
Scenario: A 5mg vial of BPC-157 is reconstituted with 2.5 mL bacteriostatic water. The research protocol specifies 250 µg per kg body weight for a 300g rat.
- Calculate reconstituted concentration: 5,000 µg ÷ 2.5 mL = 2,000 µg/mL
- Calculate animal dose: 250 µg/kg × 0.300 kg = 75 µg
- Calculate injection volume: 75 µg ÷ 2,000 µg/mL = 0.0375 mL = 37.5 µL
Unit Conversion Reference
| Unit | Equivalent |
|---|---|
| 1 mg | 1,000 µg |
| 1 mL | 1,000 µL |
| 1 mg/mL | 1,000 µg/mL |
| 1 IU (peptide hormones) | Compound-specific; check CoA |
Common Reconstitution Concentrations
| Vial size | Solvent added | Concentration | 200 µg dose volume |
|---|---|---|---|
| 5 mg | 1.0 mL | 5,000 µg/mL | 40 µL |
| 5 mg | 2.5 mL | 2,000 µg/mL | 100 µL |
| 5 mg | 5.0 mL | 1,000 µg/mL | 200 µL |
| 10 mg | 2.0 mL | 5,000 µg/mL | 40 µL |
| 10 mg | 5.0 mL | 2,000 µg/mL | 100 µL |
| 2 mg | 1.0 mL | 2,000 µg/mL | 100 µL |
Body Weight Scaling for Animal Models
Most preclinical peptide research doses are expressed per kilogram of body weight (µg/kg or mg/kg). Weigh research animals on the day of administration for accuracy. Dose volume should generally not exceed 0.1 mL per 10g body weight for subcutaneous injection in rodents (1 mL/100g for oral gavage) to avoid volume-induced stress artifacts.
Common Calculation Errors
- mg/mL vs µg/mL confusion: Always confirm units before calculating. A concentration of 2 mg/mL = 2,000 µg/mL.
- Forgetting to account for dead volume: Insulin syringes retain 5–8 µL of dead volume in the needle hub. For very small dose volumes (<50 µL), account for dead volume in syringe preparation.
- Using vial label weight as exact: Lyophilized peptide weight can vary ±5–10% from the nominal label amount. For precision studies, weigh vial contents before and after lyophilization or use manufacturer CoA reported mass.
- Not adjusting for purity: If the peptide is 95% pure, the active amount is 95% of the weighed mass. For high-precision pharmacological studies, adjust the dose calculation accordingly.
Research Disclaimer: All protocols described are intended for qualified laboratory researchers working with research-grade peptides. This content does not constitute medical advice. Bastion Peptides products are for research purposes only and are not approved for human use or therapeutic application.
