P21
What it’s used for
P21 is the name P021 is usually sold under: an experimental nerve-support (neurotrophic) peptide derived from CNTF, not the p21 cell-cycle protein. People use it for memory, focus and mood, and to protect the brain with age. All published research is in mice and lab cells; no controlled human study is known.
- Memory & focus Lab & animal research Used for memory, learning, focus and mental clarity. Cognitive effects have been seen in animal studies.
- Brain protection Lab & animal research Explored in Alzheimer's and brain-injury models for new nerve-cell growth and protecting synapses.
- Mood & resilience Community reports Used for anxiety, emotional resilience and mood support.
What to expect
Injectable
- Weeks 1–2 Subtle changes
- Weeks 2–4 Memory changes
- Weeks 4–6+ Fullest changes reported
Nasal
- Minutes–hours Short-term effects reported soon after a dose
- Weeks 1–6 Effects build up over time
Side effects & safety
Side effects
No side effects documented yet.
Stop and get help if
- Severe headache
- Neurological or mood changes
- Vomiting
- Signs of infection
- Injection-site or nasal irritation that doesn't go away, or nosebleeds
Which symptoms mean call 911 or see a doctor
Avoid or check first if
- Pregnant or breastfeeding — safety is unknown
In sport
Likely banned at all times. An early-stage research compound with no approval, so it’s an S0 substance.
Which peptides are banned in sport
How much people take
Injectable
Injectable
For every goal: Once daily · under the skin
- Cognitive enhancement 100–300 mcg
- Neuroprotection 300–500 mcg
- Initial trial & assessment 100 mcg
Similar doses appear in 2 other sources
Nasal
For every goal: Nasal
- Cognitive enhancement Once daily 500–1,000 mcg
- Acute cognitive boost As needed 1–2 mg
- Maintenance & neuroprotection Once daily 500 mcg
- Initial assessment Once daily 500 mcg
Similar doses appear in 2 other sources
How to mix and store it
How many units do I draw?
Injectable
Open the full calculator
Injectable
How to mix 5 steps with bacteriostatic water
How to mix
- 1 Wipe both tops Wash your hands, then swab the rubber tops of the peptide vial and the water vial with alcohol. Let them dry.
- 2 Draw the water Use bacteriostatic (BAC) water — sterile water with a preservative, sold for mixing peptides . With a new sterile syringe, draw the amount you entered in the calculator. A 1 mL syringe filled twice is 2 mL.
- 3 Run it down the wall Push the needle into the peptide vial at an angle and let the liquid trickle down the glass, not onto the powder.
- 4 Swirl, don’t shake Gently swirl or roll the vial until the liquid is completely clear. Give it a few minutes if needed.
- 5 Label the vial Write the date and what you mixed (for example 5 mg + 2 mL) on the vial.
This is general practice. If your product came with its own diluent or instructions, follow those. Not sure what to buy? See the supplies checklist .
Injecting under the skin Where, rotating sites, which syringe
- Where: belly (at least 2 in / 5 cm from the navel), front of the thigh, or back of the upper arm.
- Rotate sites each time and skip bruised, scarred or sore skin.
- Syringe: most people use a U-100 insulin syringe with a short, thin needle (29–31 gauge, 8 mm or shorter).
- How: wipe with alcohol and let it dry, pinch the skin, go in at 45–90°, push slowly. Use each syringe once.
General practice for under-the-skin injections, not specific to P21.
The full guide: how to inject safely
Storage
Fridge · 14–30 days Reported shelf life, not lab-tested. Mixed vial at 2–8°C (35.6–46.4°F), use within 14–30 days. Mix gently; don't shake hard
Nasal
How to mix 5 steps with bacteriostatic water · vial check
How to mix
- 1 Wipe both tops Wash your hands, then swab the rubber tops of the peptide vial and the water vial with alcohol. Let them dry.
- 2 Draw the water Use bacteriostatic (BAC) water — sterile water with a preservative, sold for mixing peptides . With a new sterile syringe, draw the amount your product calls for. A 1 mL syringe filled twice is 2 mL.
- 3 Run it down the wall Push the needle into the peptide vial at an angle and let the liquid trickle down the glass, not onto the powder.
- 4 Swirl, don’t shake Gently swirl or roll the vial until the liquid is completely clear. Give it a few minutes if needed.
- 5 Label the vial Write the date and what you mixed (for example 5 mg + 2 mL) on the vial.
This is general practice. If your product came with its own diluent or instructions, follow those. Not sure what to buy? See the supplies checklist .
Is my vial OK?
Good signs
- Clear nasal solution
Don’t use if
- Cloudy or discolored solution
Storage
Fridge · 14–21 days Reported shelf life, not lab-tested. Mixed spray at 2–8°C (35.6–46.4°F), use within 14–21 days. Dose per spray depends on the pump's actual output
Combining it with others
AI assessment Based on how each compound works, not on studies of the combination. How we assess
Use caution 1
- Dihexa Both are potent, experimental brain-growth compounds with no human safety data.
Can be combined 8
Semax NA Semax Amidate Adamax Selank Adalank PE-22-28 Bromantane Cerebrolysin
What the research says
Mostly animal studies
- No controlled human study of its effects or how the body handles it is known; human half-life is unknown.
- Mouse brain-imaging results can't show a safe human dose.
- Long-term effects of marketed P21 products on the brain and body are unknown.
- Expected timelines come from reference reports and haven't been tested in people.
- Interactions haven't been studied in people; stack ratings aren't proof that combinations are safe.
- Mixing and storage figures come from one reference source; product-specific stability hasn't been checked.
What studies found
- New mouse imaging study A 2026 3xTg-AD mouse study detected brain microstructure differences on diffusion MRI after early P021 treatment. It did not test benefit or safety in people.
How long it stays in your body
Half-life is how fast the level in your body halves — not how long effects last or how often to dose.
- Half-life
- 6 hours
- Mostly cleared
- 30 hours ≈97% gone after 5 half-lives
Reported estimate Nasal · Original source not checked.
50% left in the body
6 h after a dose
Drag to see how much is left over time.
What it’s made of
- Length
- 5 amino acids (with modifications)
- Molecular weight
- 578.3 Da
- Formula
- Not verified
An exact sequence has not been verified for this form. Reported length: 5 residues.
The exact formulation, clinical benefits and long-term safety require further verification.
Length and weight come from a reference listing and were not independently confirmed.
Sources
Sources 13
How this page was made
How it may work: Proposed LIF/STAT3 inhibition and BDNF-related neuroplasticity; adamantyl modification alters delivery.
Other names: P021 · Peptide 021 · CNTF mimetic
Preparation in studies: No product-specific preparation or stability instruction was verified.
Interaction compatibility is a reference claim, not demonstrated combination safety.
Research last checked: Oct 12, 2026 (a targeted search, not a full review).
Community doses, how long people take it, timing and storage are compiled with AI from public peptide guides, clinics and forums, cross-checked against other sources where we could, and rewritten in plain language. “Combining it with others” is an AI assessment of how the compounds work. Study notes are written from each paper’s abstract where one exists. How we source
Original source guide