Copper peptides + vitamin C
Keep them apartKeep them apart. Low-pH vitamin C can destabilize copper peptides, and copper can speed up vitamin C's oxidation - layered together, each loses potency. This one is pure chemistry: not irritating, just wasteful.
Split them: vitamin C in the morning, copper peptides at night, or alternate days.
Useful exception: SAP/MAP vitamin C derivatives (sodium ascorbyl phosphate, magnesium ascorbyl phosphate) sit at a higher pH and are more compatible with copper peptides. If your vitamin C is one of those, the pairing is much less of a problem.
Check your own shelf Add the products you actually use - Nitavera flags this pair and 14 others automatically, checks pregnancy, medication and allergy safety, and suggests your AM/PM order. Free, runs in your browser, your photo never uploads. Open the free shelf checker