The Vitamin C test measures the level of ascorbic acid, an essential water-soluble vitamin, in the blood. Vitamin C supports the formation of collagen, wound healing, immune function, and the absorption of iron, and it also acts as an antioxidant. Because the body does not make or store large amounts of vitamin C, levels depend on dietary intake. This test is used to check for low vitamin C levels, which can occur with poor diet, malnutrition, or malabsorption, and in severe cases can lead to scurvy. It may be ordered when a person has symptoms that could be related to a deficiency, such as fatigue, easy bruising, poor wound healing, or bleeding gums, or to monitor nutritional status.