This invention presents the rapid testing for nutrients in products including, but not limited, medicines, food supplements or additives, cosmetics, drinks, fruits, vegetables, and etc. The rapid testing is performed on strips coated with indicators. Nutrients such as Vitamin C can be detected in very small volume. The detection is semi-quantitative by naked eye or becomes quantitative with help of a hand-held device. The rapid testing in this invention can be very easily performed by individuals at most places, such as home, office, market, school, hospital, laboratories and etc. The rapid testing does not require expensive instruments, chemicals, or professional trainings.