All are used in the diagnosis of diabetes mellitus except:

C i.e. D-xylose absorption testGlycosylated hemoglobin (HbAic, an index of average glucose level in preceding 12 weeks), Fasting blood sugar (FBS 126 mg/dl), oral glucose tolerance test (OGTT) i.e. 2 hour post prandial glucose levels (> 200 mg/dl) and random blood sugar (RBS > 200 mg(dl) are used to diagnose diabetes mellitus whereas D-xylose absorption test is used to determine absorption of D-xylose in proximal small intestine (duodenum & jejunum) to detect intestinal malabsorption syndrome.