Peptide P21: Dosing Protocols

• Reported intranasal dosing: 100 mcg every few days (microdosing).

• Reported subcutaneous dosing: 500 mcg per day for a 10-day course.
• One protocol reconstituted a 5 mg vial with 2.5 mL of bacteriostatic water, giving 25 IU daily.

• 4 mg total daily, split as 2 mg in the morning and 2 mg at bedtime.
• Another report used 3 mg before bed.

• Frequency varied among users: daily, every few days, or in cycles.
• One user ran a cycle of about 6 weeks alongside Semax and Selank.

• Reported cognitive benefits included improved focus and memory retention.
• Users stacked P21 with Semax, Selank, and prescription stimulants.

Users reported "temporary side effects like drowsiness or mild depression, which they attribute to increased BDNF levels."

P21 is still considered experimental, and long-term effects are not well-established.

1. 01Reddit — P21 experiences: https://www.reddit.com/r/Peptides/comments/pf6r6g/p21_experiences/
2. 02Reddit — Peptide P21 dosing and general use questions: https://www.reddit.com/r/Peptides/comments/u31jm2/peptide_p21_dosing_and_general_use_questions/
3. 03Reddit — Semax, P21 and Selank with Adderall: https://www.reddit.com/r/Nootropics/comments/6zvbwx/semax_p21_and_selank_with_adderall/