Ascorbic acid (vitamin C) is used to prevent or treat low levels of vitamin C in people who do not get enough of the vitamin from their diets. … Low levels of vitamin C can result in a condition called scurvy. Scurvy may cause symptoms such as rash, muscle weakness, joint pain, tiredness, or tooth loss.
Historically, vitamin C was used for preventing and treating scurvy. These days, vitamin C is most commonly used for preventing and treating the common cold.