<prompt> Which is not a test for diabetes mellitus -Fasting blood samplingRandom blood samplingD-xyloseOral glucose tolerance test  <response>: D-xylose absorption is a laboratory test to determine how well the intestines absorb a simple sugar D-xylose. The test helps determine if nutrients are being properly absorbed. It is done in : persistent diarrhea, signs of malnutrition, unexplained weight loss. Rest of the options are the tests done in diabetes mellitus. Ref - Harrisons internal medicine 20e topic diabetes 