Laboratory tests are not always helpful in diagnosing scurvy. Clinical improvement with vitamin C supplementation, when signs and symptoms support the diagnosis of scurvy, confirms the diagnosis. Measurement of blood vitamin C levels can be helpful; however, this measurement may reflect recent dietary intake and may not accurately represent tissue vitamin C levels. A fasting blood vitamin C level of 0.6 mg/dL or higher indicates no deficiency; levels below 0.2 mg/dL suggest deficiency. Intermediate values may not allow for a definitive diagnosis. Measurement of vitamin C levels in leukocytes provides a more reliable result, as the amount of vitamin in leukocytes is less affected by dietary changes and may better reflect tissue vitamin C levels.