Animal-to-Human Dose Conversion
Educational method, not a prescription
Almost all peptide efficacy data in this base is animal (rat/mouse). A human-equivalent dose (HED) is a starting estimate for understanding the literature — not a dosing recommendation. Species differ in metabolism/half-life, anecdotal human ranges often differ, and animal “no-toxicity” ≠ human safety. Research/educational only; always with a physician.
Why you can’t use the animal mg/kg directly
Metabolic rate scales with body surface area, not body weight — so a small animal needs a higher mg/kg dose than a human to reach the same exposure. Converting requires allometric scaling, then a route adjustment, then per-person scaling.
Step 1 — Allometric scaling (FDA Kₘ method)
HED (mg/kg) = Animal dose (mg/kg) × (Kₘ animal ÷ Kₘ human)
| Species | Kₘ | Shortcut ×factor → human |
|---|---|---|
| Mouse | 3 | ×0.081 |
| Rat | 6 | ×0.162 |
| Rabbit | 12 | ×0.324 |
| Dog | 20 | ×0.541 |
| Human (60 kg) | 37 | — |
(This is the source of the “×0.162” you’ll see for rat studies in the transcripts.)
Step 2 — Route / bioavailability adjustment
Most animal studies inject intraperitoneally (IP), which is ~40% more bioavailable than subcutaneous → to match exposure, SubQ dose ≈ HED × 1.4. Other routes: IV = 100%; SubQ ≈ 70% of IV; oral varies (e.g. acid-resistant BPC-157 oral ≈ half of SubQ; most other peptides far lower).
Step 3 — Per-kg → per-person
Multiply the adjusted mg/kg by body weight (typically 70–80 kg).
Step 4 — Sanity-check + safety factor
Drug development often ÷10 as a safety margin for a first human dose. Compare the result to anecdotal human ranges (which frequently run higher) and start low, titrate slow. See Dosing & Titration.
Worked examples (already derived in our transcripts)
| Peptide | Animal dose | Conversion | Human-equivalent | Anecdotal human range | Source |
|---|---|---|---|---|---|
| BPC-157 | 10 mcg/kg rat IP | ×0.162 → 1.62, ×1.4 (IP→SubQ) → 2.27 mcg/kg | ~181 mcg/day (80 kg) | 250–500 mcg/day SubQ | TRANSCRIPT-bpc157-deep-dive |
| MOTS-C | 0.5 mg/kg/day IP | → ~0.048 mg/kg SubQ | ~3.33 mg/day → ~23 mg/week | ~5 mg 3×/week | TRANSCRIPT-mots-c-deep-dive |
| TB-500 / TB4 | 6 mg/kg rat IP | ×0.162 → 0.49, ×1.4 → ~0.69 mg/kg → ~48 mg/day (impractically high) → re-anchored to human IV-safety 5 mcg/kg | ~500 mcg/day SubQ | 250–500 mcg/day | TRANSCRIPT-tb4-tb500-deep-dive |
| SS-31 | 3 mg/kg mouse (anti-aging) | allometric HED | ~17 mg/day; a 1 mg/kg study → ~6 mg/day | start 5–10 mg/day (studies used 40 mg/day in extreme-dysfunction populations) | TRANSCRIPT-ss31-deep-dive |
| Selank | 100 mcg/kg/day | →16.2 mcg/kg → ~1 mg/day; ÷10 safety → ~100 mcg/day start | 250–900 mcg intranasal (human studies) | TRANSCRIPT-selank-deep-dive | |
| GHK-Cu | 0.5 mg/kg EOD IP | allometric + IP→SubQ | ~0.6–1 mg/day SubQ | 0.5–2 mg/day | TRANSCRIPT-ghk-cu-deep-dive |
Posting convention for animal-study notes
When a kb-paper or peptide note records an animal dose, also record the HED breakdown (animal dose → Kₘ scaling → route adjustment → per-person), with the anecdotal human range and a “start-low” caveat — so the jump from animal protocol to human protocol is always explicit and traceable, never a bare number.
Caveats
HED is a modeling estimate, not a target. Half-life, receptor desensitization, and bioavailability differ by species and route. Anecdotal human doses are not validated. None of this is medical advice.