Peptide Dosing Guide

This guide provides graduate-level coverage of peptide dosing principles, from fundamental pharmacokinetic concepts to practical clinical dosing tables for 20+ peptides.

Dose Calculation Principles

Fundamental Pharmacokinetic Relationships

Peptide dosing is governed by the relationship between dose, concentration, and volume of distribution:

Where:

• = plasma concentration (ng/mL)
• = dose (mg or mcg)
• = bioavailability (fraction)
• = volume of distribution (L)

For peptides, bioavailability varies dramatically by route:

• Intravenous: (100%)
• Subcutaneous: (50–100%)
• Intramuscular: (70–100%)
• Intranasal: (1–15%)
• Oral: (0.1–10%)

Clearance and Half-Life

The dosing interval is determined by the elimination half-life ():

Where:

• = clearance (L/hr)
• = volume of distribution (L)

At steady state, the accumulation factor () for repeated dosing is:

Where = elimination rate constant and = dosing interval.

Target Concentration Approach

For peptides with well-defined therapeutic windows, dosing targets a specific plasma concentration range:

This equation enables calculation of the dose required to achieve and maintain a target concentration, accounting for the peptide’s pharmacokinetic properties and desired dosing interval.

Body Weight-Based Dosing

Many peptides are dosed on a microgram-per-kilogram (mcg/kg) basis, particularly those with narrow therapeutic windows or when initiated in diverse patient populations.

Standard Weight-Based Dosing Formula

Example Calculations

Example 1: CJC-1295 DAC

• Target dose: 30 mcg/kg SC daily
• Patient weight: 80 kg
• Dose = 80 × 30 = 2,400 mcg = 2.4 mg

Example 2: Ipamorelin

• Target dose: 200 mcg SC 2× daily
• Patient weight: 70 kg
• Dose = 200 mcg per injection (fixed dose, not weight-adjusted)

When to Use Weight-Based vs Fixed Dosing

Factor	Weight-Based	Fixed Dose
Narrow therapeutic index	Preferred	Less appropriate
Extreme body weights	Preferred	May be inaccurate
Pediatric patients	Required	Not appropriate
Elderly patients	Preferred (adjusted)	May be acceptable
Wide therapeutic window	Either	Often preferred
Convenience	Less convenient	More convenient

Fixed Dosing Protocols

Fixed dosing simplifies administration and improves adherence by eliminating dose calculations. Fixed dosing is appropriate when:

1. The therapeutic window is wide
2. Efficacy is not strongly weight-dependent
3. Pharmacokinetic variability exceeds body weight effects
4. Patient convenience is a priority

Examples of Fixed-Dose Peptides

Peptide	Fixed Dose	Rationale
Semaglutide	0.25–2.4 mg weekly	Wide therapeutic window
Liraglutide	0.6–3.0 mg daily	Weight-independent efficacy ceiling
BPC-157	250–500 mcg 2× daily	Wide safety margin
TB-500	2.5–5 mg 2× weekly	Dose-response plateau

Dose Escalation Strategies

Dose escalation serves two purposes:

1. Mitigating side effects (start low, go slow)
2. Reaching therapeutic targets (titrate to effect)

Escalation Schedules

Standard Escalation (GLP-1 Receptor Agonists)

Week	Semaglutide SC	Liraglutide	Tirzepatide
1–4	0.25 mg weekly	0.6 mg daily	2.5 mg weekly
5–8	0.5 mg weekly	1.2 mg daily	5 mg weekly
9–12	1.0 mg weekly	1.8 mg daily	10 mg weekly
13–16	1.7 mg weekly	2.4 mg daily	15 mg weekly
17+	2.4 mg weekly	3.0 mg daily	15 mg weekly

Conservative Escalation (GH Secretagogues)

Week	CJC-1295 DAC	Ipamorelin
1–2	15 mcg/kg daily	100 mcg 1× daily
3–4	30 mcg/kg daily	200 mcg 1× daily
5–6	30 mcg/kg daily	200 mcg 2× daily
7+	30–60 mcg/kg daily	200–300 mcg 2× daily

Aggressive Escalation (When Rapid Titration Needed)

Week	Peptide	Dose
1	Starting dose	50% of target
2	Target dose	100%

Escalation Decision Points

Factor	Escalate If	Hold/Reduce If
Efficacy	Suboptimal response at current dose	Target achieved
Tolerability	Side effects resolved	Intolerable side effects
Biomarkers	Target not met (e.g., IGF-1, HbA1c)	Target exceeded
Time at dose	≥4 weeks at current dose	<2 weeks at current dose

Therapeutic Window Concepts

Therapeutic Index

The therapeutic index (TI) determines dosing flexibility:

Where:

• = dose producing toxicity in 50% of patients
• = dose producing efficacy in 50% of patients

Peptide Class	Typical TI	Dosing Implications
Insulins	Narrow (2–5×)	Precise dosing required
GLP-1 agonists	Wide (10–20×)	Flexible dosing, escalation tolerated
GH secretagogues	Moderate (5–10×)	Monitor IGF-1
Thymic peptides	Wide (>20×)	Dose flexibility acceptable
BPC-157	Very wide (>50×)	Wide dosing range acceptable

Therapeutic Drug Monitoring

For peptides with narrow therapeutic windows, therapeutic drug monitoring (TDM) guides dosing:

Peptide	Therapeutic Range	Monitoring Frequency
Insulin	Glucose-guided	Daily (self-monitoring)
Semaglutide	Weight/HbA1c-guided	Every 4–12 weeks
CJC-1295 + Ipamorelin	IGF-1: 150–300 ng/mL	Every 4–8 weeks
Thymosin Alpha-1	CD4/CD8 ratio	Every 4–12 weeks

Dose-Response Relationships

Linear Dose-Response

Some peptides exhibit linear dose-response curves where increasing dose proportionally increases effect:

Example: Insulin glucose lowering (within physiological range)

Emax Dose-Response (Saturation)

Most peptides exhibit saturable dose-response curves:

Where = Hill coefficient (steepness of curve)

Example: Semaglutide weight loss (plateaus at higher doses)

Practical Implications

Dose-Response Type	Clinical Implication
Linear	Dose increases produce proportional benefit
Emax (flat curve)	Dose increases beyond ED50 produce diminishing returns
Emax (steep curve)	Small dose changes produce large effect changes

Clinical Dosing Tables

Insulin Analogs

Insulin	Route	Onset	Peak	Duration	Typical Dose
Lispro	SC	5–15 min	1–2 hrs	3–5 hrs	Per carb ratio
Aspart	SC	10–20 min	1–2 hrs	3–5 hrs	Per carb ratio
Glulisine	SC	10–20 min	1–2 hrs	3–5 hrs	Per carb ratio
Glargine U-100	SC	1–2 hrs	8–12 hrs	24 hrs	10–80 U daily
Glargine U-300	SC	2–6 hrs	12–18 hrs	30–36 hrs	10–80 U daily
Degludec	SC	1–2 hrs	Flat	>42 hrs	10–80 U daily
Detemir	SC	1–2 hrs	3–8 hrs	16–24 hrs	10–80 U 1–2× daily

GLP-1 Receptor Agonists

Peptide	Route	Frequency	Starting Dose	Target Dose	Max Dose
Semaglutide (SC)	SC	Weekly	0.25 mg	1.0–2.4 mg	2.4 mg
Semaglutide (oral)	Oral	Daily	3 mg	7–14 mg	14 mg
Liraglutide	SC	Daily	0.6 mg	1.8–3.0 mg	3.0 mg
Dulaglutide	SC	Weekly	0.75 mg	1.5 mg	4.5 mg
Tirzepatide	SC	Weekly	2.5 mg	10–15 mg	15 mg
Exenatide ER	SC	Weekly	2 mg	2 mg	2 mg
Exenatide IR	SC	Twice daily	5 mcg	10 mcg	10 mcg

GH Secretagogues

Peptide	Route	Frequency	Starting Dose	Target Dose	Max Dose
CJC-1295 DAC	SC	Daily	15 mcg/kg	30 mcg/kg	60 mcg/kg
Ipamorelin	SC	1–3× daily	100 mcg	200 mcg	300 mcg
GHRP-2	SC	1–3× daily	100 mcg	200 mcg	300 mcg
GHRP-6	SC	1–3× daily	100 mcg	200 mcg	300 mcg
Sermorelin	SC	Daily (bedtime)	100 mcg	300 mcg	500 mcg
Tesamorelin	SC	Daily	0.5 mg	2 mg	2 mg
MK-677	Oral	Daily	10 mg	25 mg	50 mg

Tissue Repair Peptides

Peptide	Route	Frequency	Typical Dose	Duration
BPC-157	SC/IM/Oral	1–2× daily	250–500 mcg	2–12 weeks
TB-500	SC/IM	2× weekly	2.5–5 mg	4–8 weeks
GHK-Cu	SC/Topical	1–2× daily	1–5 mg	4–12 weeks
Thymosin Beta-4	SC/IM	Daily	2.5–5 mg	4–8 weeks

Thymic Peptides

Peptide	Route	Frequency	Typical Dose	Duration
Thymosin Alpha-1	SC/IM	1–2× daily	1.6 mg	1–6 months
Thymulin	SC/IM	1–2× daily	50–100 mcg	1–3 months

Metabolic Peptides

Peptide	Route	Frequency	Starting Dose	Target Dose
Tesamorelin	SC	Daily	0.5 mg	2 mg
AOD-9604	SC	Daily	250 mcg	500 mcg
5-Amino-1MQ	Oral	Twice daily	50 mg	100 mg

Sexual Health Peptides

Peptide	Route	Frequency	Typical Dose	Timing
PT-141 (Bremelanotide)	SC/IN	As needed	1.75 mg SC / 7.5 mg IN	45 min before
Oxytocin	IN	As needed	24–40 IU	15–30 min before

Melanocortin Peptides

Peptide	Route	Frequency	Loading Dose	Maintenance
Melanotan I	SC	Daily → 2–3×/wk	0.5–1 mg daily × 10–14 days	0.5–1 mg 2–3× weekly
Melanotan II	SC	Daily → 2–3×/wk	0.5–1 mg daily × 10–14 days	0.5–1 mg 2–3× weekly
Afamelanotide	Implant	Every 2 months	16 mg	16 mg q2 months

Conversion Between Mass, Volume, and Units

Mass-to-Volume Conversion

For reconstitution, the relationship between mass, concentration, and volume is:

Common Reconstitution Examples

Vial Size	BAC Volume	Concentration	100 mcg	250 mcg	500 mcg
1 mg	1 mL	1 mg/mL	0.1 mL	0.25 mL	0.5 mL
2 mg	1 mL	2 mg/mL	0.05 mL	0.125 mL	0.25 mL
5 mg	2 mL	2.5 mg/mL	0.04 mL	0.1 mL	0.2 mL
10 mg	2 mL	5 mg/mL	0.02 mL	0.05 mL	0.1 mL
50 mg	2 mL	25 mg/mL	—	—	0.02 mL

Unit Conversion Reference

Conversion	Formula	Example
mg to mcg	× 1,000	0.5 mg = 500 mcg
mcg to mg	÷ 1,000	250 mcg = 0.25 mg
mL to uL	× 1,000	0.5 mL = 500 uL
IU to mg	Peptide-specific	100 IU insulin = 3.47 mg

Insulin Unit Conversion

Insulin units are defined by biological activity, not mass. Conversion factors:

Insulin	Units per mg
Regular (human)	26 U/mg
Lispro	26 U/mg
Aspart	26 U/mg
Glargine	26 U/mg
Degludec	26 U/mg
Detemir	26 U/mg

Therefore: 100 units ≈ 3.47 mg for all standard insulin formulations.

Special Populations

Renal Impairment

GFR (mL/min)	Dose Adjustment
>50	No adjustment
30–50	Reduce dose by 25–50%
<30	Reduce dose by 50–75%
Dialysis	Avoid or use with caution

Hepatic Impairment

Severity	Dose Adjustment
Mild	No adjustment
Moderate	Reduce dose by 25%
Severe	Reduce dose by 50% or avoid

Elderly (≥65 years)

Factor	Adjustment
Renal function	Check CrCl, adjust accordingly
Body composition	May need lower doses (less lean mass)
Sensitivity	Often increased sensitivity
Starting dose	Reduce by 25–50%

Pediatric

Age	Considerations
Neonates	Weight-based dosing required
Children	Weight-based; adjust for development
Adolescents	Adult dosing may be appropriate

Key Principles Summary

1. Start low, go slow — Begin at 50% of target dose and escalate over 2–4 weeks
2. Monitor biomarkers — IGF-1 for GH secretagogues, glucose for insulins, HbA1c for GLP-1 agonists
3. Account for bioavailability — Route-dependent F values dramatically affect effective dose
4. Consider accumulation — Long half-life peptides require 4–5 half-lives to reach steady state
5. Adjust for organ function — Renal and hepatic impairment require dose reduction
6. Individualize — Population averages are starting points; individual response varies