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Prescription topical: a pea-sized amount of 0.025%-0.1% cream or gel applied to clean, dry skin once nightly. Start low-strength and every-other-night to build tolerance. A prescription drug used under clinician direction — not a supplement regimen.

Before bed

Topical cream or gel, 0.025%-0.1% (prescription)

Topical cosmetic only. L-ascorbic acid serums are typically 10-20% (often near pH 3 for absorption); stable derivatives are used at varying percentages. Apply a few drops to clean, dry skin, usually in the morning under sunscreen (its antioxidant action complements SPF). There is no oral, injectable, or systemic dose in this cosmetic context. This library does not provide an ingestion protocol.

Morning

Leave-on topical serum (10-20% L-ascorbic acid) or a stable vitamin C derivative

• Pregnancy and planning pregnancy (topical retinoid — avoid)
• Breastfeeding (avoid application near areas of infant contact)
• Eczema / rosacea-prone or broken/sunburned skin (irritation)

• Benzoyl peroxide
• Other topical exfoliants (AHAs / BHAs, abrasives)
• Photosensitizing drugs

• For topical (skin) use only — not for ingestion, not for injection (in this cosmetic context)
• Known allergy or sensitivity to the formulation
• Application to broken, irritated, or compromised skin until healed

• Strong leave-on actives (retinoids, AHAs/BHAs, benzoyl peroxide)
• Niacinamide