Fasting Blood Glucose
Advantages: - is established as the current diagnostic means for diabetes; - is a direct measure of glycemia (which the patients are used to); - is more available than A1c globally; - it has less between-laboratories variability than A1c; - is not affected by non-glycemic factors as is A1c	Disadvantages: - is a single time point of glycemia (thus static rather than chronic); - requires fasting (which adds to its inconvenience); - has more within-individual variability than A1c; - has a sub-optimal sensitivity; - requires prompt processing after blood drawing to avoid artifacts
Oral Glucose Tolerance Test
Advantages: - is established as the current diagnostic means for diabetes; - is a direct glycemic measure; - is more available than A1c globally; - has less between-laboratories variability than A1c; - is not affected by non-glycemic factors as is A1c.	Disadvantages: - is a single time point of glycemia; - requires fasting; - has more within-individual variability than A1c; - requires prompt processing after blood drawing to avoid artifacts; - is cumbersome, multi-staged, inconvenient; - the displeasing taste of the concentrated glucose drink; especially for pregnant women; - is unreliable in patients with gastric bypass
Hemoglobin A1c
Advantages: - is more convenient, since fasting is not required; - has greater pre-analytical stability, and less day-to- day changes that can cause significant excursions in plasma glucose; - is established as a monitoring measure of diabetes control; - is more stable for subsequent measurement.	Disadvantages: - can be affected by factors that can affect the lifespan of the erythrocytes (e.g., iron deficiency anemia, blood loss, chronic kidney failure, and erythropoietin therapy as used in renal failure and sometimes in chronic anemia); - can be affected by hemoglobin variants (assay method dependent); - can demonstrate variability due to differences in glycation rates; - can be affected by HIV; - is less available globally than glucose tests.