For 4 weeks. The Vitamin C is encapsulated in the protective cap to preserve its properties intact until use. Before applying, activate the Vitamin C by following these two steps: - Remove the safety cap and replace it with the one containing the pure Vitamin C capsule. - Press the bottle cap all the way. This will release Vitamin C. - Shake vigorously for 1-2 minutes and set for 2 minutes more before replacing the cap with the dropper. After two minutes, you can apply it at night on clean, dry skin. Spread evenly across the face using gentle massages until fully absorbed. Each bottle is designed for 7 days of treatment. To keep the skin in optimal condition, we recommend repeating the treatment every 4 months.