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An evidence-based peptide reference
Research reference only. Not medical advice. Most compounds are not FDA-approved. These are research chemicals, not for human consumption. Consult a qualified clinician.Read methodology

Combinations to avoid

Combinations flagged to avoid

Pairings the interaction engine flags because the compounds duplicate one target, push the same hormone axis twice, or carry a documented hazard together. Each page states the mechanism behind the flag and the source it rests on.

All 11 flagged combinations 11

  • GH secretagogues combined with exogenous HGHRisk: Moderate-High

    Negative feedback via somatostatin/IGF-1; risk of pituitary suppression; diminishing returns on GH output

  • GLP-1 agonist + insulin or sulfonylureasRisk: High

    Hypoglycemia risk: GLP-1 enhances glucose-dependent insulin secretion; stacking with exogenous insulin or secretagogues can drive severe lows

  • Melanotan II combined with novel peptides during dose-findingRisk: High

    Masks individual peptide response (pigmentation, nausea, BP overlap); MC1R activation raises melanoma/mole darkening concerns when dose-finding other compounds

  • Semaglutide + Liraglutide combinedRisk: Moderate

    Redundant GLP-1 receptor activation: both molecules occupy the same target with no published combination-therapy precedent.

  • Semaglutide + Tirzepatide combinedRisk: High

    Overlapping GLP-1 pathway: stacks side effects (GI, pancreatitis) with no added efficacy; FDA-flagged as unsafe combination

  • Two GHRHs in the same regimenRisk: Moderate

    Same receptor: competition at pituitary GHRH receptor; no additive benefit, reduced efficiency

  • Two GHRPs in the same regimenRisk: Moderate

    Ghrelin receptor (GHS-R1a) saturation + accelerated desensitization; may blunt long-term GH response

  • Two GIP agonists in the same regimenRisk: High

    Overlapping GIP receptor activation on the same incretin pathway: stacks GI side effects, pancreatitis signal, and gallbladder risk with no added efficacy.

  • Two glucagon-receptor agonists in the same regimenRisk: High

    Overlapping glucagon-receptor activation drives hepatic glucose output, hepatic lipid mobilization, and resting heart rate; stacking compounds metabolic and cardiovascular load with no clinical precedent

  • Two IGF-1 analogs in the same regimenRisk: Moderate-High

    Multiple IGF-1 analogs compete for the same IGF-1R pool; the second analog does not raise peak receptor activation but stacks hypoglycemia exposure, cardiac/renal/hepatic hypertrophy signal, and peripheral neuropathy risk in heavy stacks

  • Two MC1R agonists in the same regimenRisk: Moderate-High

    Overlapping MC1R activation compounds melanogenesis, mole darkening, and the documented atypical-nevus / melanoma signal seen with chronic melanocortin exposure; the safety signal scales with cumulative MC1R activation