Vitamin C absorption test measures tissue ascorbic acid levels. These levels correlate well with blood plasma levels and by association is a good measurement of antioxidant reserves in the body. A poor tissue ascorbic acid level indicates low antioxidant reserves. Vitamin C is a strong antioxidant but is also a complex nutrient that requires many other nutrients and minerals to enhance it’s absorption as well as its activity. Antioxidants support proper body functions, protect cells from damage and have an anti-aging effect on the body.