A 48-year-old female patient presented with the following laboratory results: fasting glucose of 133 mg/dL, postprandial glucose of 309 mg/dL, hemoglobin level of 10.30 g/dL, PCV (packed cell volume) of 33.20%, MCV (mean corpuscular volume) of 71.50 fL, MCH (mean corpuscular hemoglobin) of 22.20 pg, MCHC (mean corpuscular hemoglobin concentration) of 31.00 g/dL, RDW (red cell distribution width) of 16.90%, and a mean platelet volume of 12.7 fL. Based on the fasting and postprandial glucose levels, what diagnosis can be suspected, and what further tests or actions would you recommend for this patient?