<prompt> All are used in the diagnosis of diabetes mellitus except:FBSHbAlcD-xylose absorption testOGTT  <response>: C i.e. D-xylose absorption testGlycosylated hemoglobin HbAic, an index of average glucose level in preceding 12 weeks, Fasting blood sugar FBS 126 mgdl, oral glucose tolerance test OGTT i.e. 2 hour post prandial glucose levels 200 mgdl and random blood sugar RBS 200 mgdl 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. 