Type 1 Diabetes: Diagnosis

Also known as: GCT; 50 gram glucose challenge; one-hour glucose screening test.

What is it? A screening test that measures blood glucose levels one hour after 50 grams of a glucose solution has been consumed (an extremely sweet drink). If the GCT is elevated, it indicates the need for further testing.

Why is this test performed? To screen for gestational diabetes in pregnant women considered "at risk."

How frequently should this test be performed? Once. If results are abnormal and glucose levels elevated, it should be followed up by a 3-hour oral glucose tolerance test (OGTT).

What is the "normal" range for results? Normal values are 140 mg/dl or less.

What do abnormal results mean? A glucose threshold value >140 mg/dl (7.8 mmol/l) means that gestational diabetes is a possibility and an OGTT is indicated.