The following is used for testing absorption in intestine -
D-xylose absorption test is used to check how well your intestines are absorbing a simple sugar called D-xylose. From the results of the test, your doctor can infer how well your body is absorbing nutrients. D-xylose is a simple sugar that occurs naturally in many plant foods. Ref Davidson edition23rd pg 822
Xylose
Sucrose
Fructose
Maltose
G.I.T