Natural Factors C Extra + Quercetin Bioflavonoids is an immune-support formula that combines the antioxidant benefits of vitamin C and the bioflavonoid quercetin in a synergistic 2:1 ratio. Vitamin C helps in collagen formation to maintain healthy bones, cartilage, teeth, and gums, while quercetin enhances the activity of vitamin C in the body. Quercetin is currently being studied for additional health benefits. Ingredients Suggested Use Vitamin C (ascorbic acid) 500 mg, Quercetin (bioflavonoids) 250 mg Vegetarian capsule (carbohydrate gum [cellulose], purified water), microcrystalline cellulose, vegetable grade magnesium stearate (lubricant), stearic acid, silica. Adults take 1 capsule daily with food or as directed by a health care practitioner. Consult a health care practitioner for use beyond 12 weeks.