Why didn't you ask your doc to explain it to you? It's called a glucose test. I did mine yesterday. They will have you drink this really sugary drink (tastes like flat soda) about an hour before your appt. Then they draw your blood and test it to determine if you have gestational diabetes. The doc should tell you this but make sure the day that you take the test you don't eat anything sugary for breakfast, as that will raise your sugar levels even more.