Díaz Lab Testing Store › HbA1c | Whole Blood (Quest) Image 1 of 1 HbA1c | Whole Blood (Quest) $27.00 Three-month average blood sugar — the gold standard for diabetes screening and monitoring. Add To Cart Added! Three-month average blood sugar — the gold standard for diabetes screening and monitoring. Add-on | Interpretation for Individual Markers $17.00 Add Added!