Don't buy blends or gummies - they pose a higher risk. Also, don't buy from most random low-volume brands, although there are some good exceptions, e.g. ProHealth. Real vitamin C capsules containing ascorbic acid turn from white to brown with age over a few months of a bottle being open. For this reason, never buy a very large bottle of it. Also, the taste of vitamin C is very characteristic. If it has turned brown,…
Real vitamin C capsules turn from green (usually, occasionally yellow or orange) to brown over a few days if not refrigerated. Also the taste is very characteristic: apple-flavored, orange-flavored, lemon-flavored, etc.