Does my body weight affect peptide dosing?
Sometimes. Most strength peptides use fixed doses regardless of body weight, but IGF-1 LR3, Tesamorelin, and a few others scale with size. Here's the breakdown.
Updated May 27, 2026 · 5 min read
Sometimes. Most strength peptides use fixed doses regardless of body weight — BPC-157 at 250 mcg, Ipamorelin at 200 mcg, Sermorelin at 200–500 mcg. These work essentially the same across a 120-lb athlete and a 240-lb athlete because they act on receptors that don't scale linearly with body mass.
A smaller set of peptides — IGF-1 LR3, Tesamorelin, and dose-sensitive systemic compounds — do warrant some scaling with body weight. The honest answer is that the strength-peptide community's dosing conventions are mostly empirical and weight-independent, and the cases where weight matters are specific rather than general.
Why most peptides use fixed doses
Drug dosing scales with body weight when the drug:
- Distributes throughout body water or lean mass
- Acts at concentrations proportional to plasma levels
- Has a narrow therapeutic window where overshooting matters
Most strength peptides don't meet all three criteria:
- They often act through specific receptors where binding saturates at therapeutic doses
- Plasma concentrations matter less than tissue-level effects
- The therapeutic window is wide for most healing peptides
For BPC-157, doubling the dose in a heavier user doesn't double the tendon-healing effect — the receptor or local concentration where the peptide does its work is already saturated at the lower dose.
For the broader dosing framework see BPC-157 dosing protocols and math basics for reconstitution.
Peptide-by-peptide guide
| Peptide | Dose adjustment for weight? | Notes |
|---|---|---|
| BPC-157 | No | 250 mcg standard; site-specific scaling matters more than body weight |
| TB-500 | Minor | 2–5 mg per dose; heavier users sometimes use upper range |
| GHK-Cu | No | Standard doses; topical use is per-area not per-weight |
| KPV | No | Standard 250–500 mcg |
| Ipamorelin | No | 200–300 mcg regardless of weight |
| CJC-1295 (no DAC) | No | 100–200 mcg standard |
| CJC-1295 with DAC | Minor | Heavier users may use 2 mg vs 1 mg per weekly dose |
| Sermorelin | No | 200–500 mcg standard |
| Tesamorelin | Yes | 1–2 mg standard; some clinical use scales with body composition |
| MK-677 | Minor | 12.5–25 mg range may scale modestly with body mass |
| IGF-1 LR3 | Yes | Often dosed in mcg/kg in research; community sometimes follows |
| IGF-1 DES | Yes | Site-specific dosing matters more than body weight |
| MOTS-c | Minor | 5–10 mg standard, some scaling for very heavy users |
| SS-31 | Minor | Similar to MOTS-c |
| AOD-9604 | No | 300 mcg fasted AM standard |
| HGH Frag 176-191 | No | 250–500 mcg fasted AM standard |
| DSIP | No | 100–300 mcg pre-bed |
| Selank / Semax | No | Standard intranasal or SubQ doses |
| Hexarelin | Minor | 100 mcg standard, lower in lighter users |
The cases where weight matters
IGF-1 LR3 is the clearest example. Research protocols often dose IGF-1 LR3 in mcg/kg rather than fixed doses. Community use sometimes follows this convention:
- Light user (60 kg / 130 lb): 20–30 mcg/day
- Mid user (80 kg / 175 lb): 30–40 mcg/day
- Heavy user (100 kg / 220 lb): 40–60 mcg/day
The scaling is loose — IGF-1 LR3 has a wide therapeutic window — but heavier users do tend to use higher doses to achieve similar circulating IGF-1 elevation.
Tesamorelin is dosed at 1 mg or 2 mg per day standard. Heavier users with significant visceral adipose may benefit from the 2 mg dose; lighter users do fine on 1 mg. The dose-response was studied in heterogeneous body sizes in the original trials.
MK-677 at 12.5 mg vs 25 mg sometimes scales with body weight, though the dose-response is more about side-effect tolerance (hunger, water retention) than therapeutic effect.
TB-500 at the upper end of its 2–5 mg range may serve heavier users better in injury protocols.
What about very lean or very heavy users?
Very lean users (low BMI, low body fat):
- Standard doses often work fine
- Reduced subcutaneous tissue may make injection slightly more uncomfortable
- Visceral effect peptides (Tesamorelin) have less work to do — lower doses may suffice
Very heavy users (high BMI, high body fat):
- Standard doses still typically work
- For visceral fat-targeted compounds (Tesamorelin), heavier users may need the higher dose range
- Caloric intake and metabolic context matter more than body weight for adjustment
Bodybuilders and very muscular users:
- IGF-1 LR3 is the peptide where their higher muscle mass may warrant slightly higher doses
- GH secretagogues remain at standard doses — the pituitary's secretory capacity isn't directly proportional to skeletal muscle
For dosing math see the reconstitution math basics and the site's calculator.
The "more is better" mistake
A common mistake: "I'm 220 lbs so I should double the dose."
This usually doesn't work because:
- Most peptide receptors saturate at therapeutic doses — doubling produces diminishing returns
- Higher doses increase side-effect probability (water retention, hunger, headaches) more than they increase benefit
- Faster receptor downregulation occurs at higher doses (especially for GH-axis peptides)
If standard doses aren't producing the response you want, the answer is usually not "double the dose." It's:
- Audit timing and consistency (see GH peptide non-responders)
- Audit vendor quality (see vendor due diligence checklist)
- Consider switching mechanism (different peptide, different pathway)
- Accept that response is what it is
For the broader troubleshooting see GH peptide non-responders.
The practical bottom line
For most users at most doses:
- Standard fixed doses are appropriate regardless of body weight
- Scaling matters most for IGF-1 LR3 (mcg/kg), Tesamorelin (1 vs 2 mg), and a few edge cases
- "I'm heavier so I should take more" is usually wrong; "I'm lighter so I should take less" is closer to correct
When in doubt, start at the lower end of the recommended range and adjust based on response and tolerability.