Not medical advice. Talk to your provider before using any peptide.
Full disclaimerPeptide Schedule Research TeamReviewed Apr 20265 Citations
P21Small moleculeNo amino acid sequence. Icon reflects category theme only.P21 is a CNTF-derived tetrapeptide that tripled hippocampal neurogenesis and cut tau hyperphosphorylation by 50 to 60% in Alzheimer's mouse models. Strictly preclinical. No human trials. Community reports favor intranasal dosing at 500 mcg to 1 mg daily for subtle memory support over 4 to 6 week cycles.
100mcg · Daily
Summary: Add 2mL BAC water to your 5mg vial. Draw to 4.0 units on a U-100 syringe for a 100mcg dose. This vial will last 50 doses.
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| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 100mcg | Daily |
| Moderate | 300mcg | Daily |
| Aggressive | 500mcg | Daily |
Start subcutaneous if you want to test the waters cheaply. But know that a lot of community users gave up on SC at beginner doses and only found the compound useful intranasally. Reconstitution math for SC: take a 10 mg vial, add 2 mL bacteriostatic water. That gives you 5 mcg per microliter. For the beginner dose (100 mcg), draw 20 units on a U100 insulin syringe. For moderate (300 mcg), draw 60 units. For aggressive (500 mcg), draw 100 units, which is the full syringe. A 5 mg vial with 2 mL BAC water gives 2.5 mcg per microliter; double the units for the same dose. Intranasal is a different calculation entirely. Reconstitute a 5 mg vial with 1 mL BAC water for 5 mg/mL concentration. Each 0.1 mL spray delivers 500 mcg. At the community top protocol of 1 mg/day, a 5 mg vial lasts five days. A 10 mg vial lasts ten days. That's why intranasal cycles get expensive fast, running $18 to $30 per day at 1 mg. Don't expect to feel anything for at least two weeks. Track with objective tools: spatial recall tests, word-pair memory tasks, mental rotation exercises. Subjective "feel" is unreliable with this compound.
Dosing based on Very limited human data: dose based on preclinical and anecdotal reports — 8 published references.View all sources →
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Pricing updated 2026-04-09
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P21 is a CNTF-derived tetrapeptide that tripled hippocampal neurogenesis and cut tau hyperphosphorylation by 50 to 60% in Alzheimer's mouse models. Strictly preclinical. No human trials. Community reports favor intranasal dosing at 500 mcg to 1 mg daily for subtle memory support over 4 to 6 week cycles.
