During a physical exam, your doctor likely will take your medical and family history, and have you take one or more blood tests to measure your blood sugar levels. This would include a fasting plasma glucose (FPG) test, which requires that you not eat for at least 6 hours prior to the test. Additionally, your doctor will probably order glycated hemoglobin (HbA1c or A1c) blood tests. A1c tests measure your average blood sugar levels for the past 2-3 months.
It is also common for your doctor to check your urine for ketones, which are fatty acids that appear when you have high blood sugar levels.
Sometimes, type 1 diabetes is diagnosed in the emergency room after a person develops diabetic ketoacidosis (DKA). This condition develops when you don't get enough insulin, your blood sugar level rises sharply and kteones build up in your blood. Symptoms of DKA may include severe and sudden nausea, vomiting and stomach pain.
Whether you are diagnosed in an emergency department or at your doctor's office, be sure to tell your doctor about any and all symptoms you've experienced, such as frequent urination, excessive thirst, even trouble concentrating.
Because you may have health conditions related to type 1 diabetes, expect your doctor to run other tests, such as a fasting lipid profile—a test that measures the fats in your blood after a 12-hour fast (no food or drink, except water). Your doctor will also check other areas of your body such as your feet, eyes, heart and kidneys.