For the glucose challenge test, the patient receives 50 g of glucose. One hour later, blood is drawn for a plasma glucose determination. A glucose value above 130 to 140 mg/dL is considered abnormal and necessitates a second test, the 3-hour glucose tolerance test. Our center uses 140 mg/dL as the cutoff point. Abnormal results for the 1-hour screening test will occur in 15% of patients. Of those patients who go on to have the 3-hour screening test, 15% will be diagnosed with GDM.