Ester-C® is a breakthrough patented Vitamin C formula supported with naturally occurring metabolites. Metabolites help enhance the absorption of Vitamin C by your white blood cells, an important part of your immune system. Ester-C®'s unique, chemical-free manufacturing process neutralizes pH, making it non-acidic and gentle on the stomach.* In a daily 1,000 mg dose, Ester-C® delivers 24-hour immune support...so once a day is all you need. Added Citrus Bioflavonoids may help your body better absorb and utilize Vitamin C.