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 - Northwestern Memorial Hospital - Chicago

Tests & Diagnosis

Tests for Type 1 & Type 2 Diabetes

The latest recommendation for diabetes testing involves a blood test that measures the average of your blood sugar level over a period of time. This test is called the glycated hemoglobin (A1c) test, and it is also known as:

  • Hemoglobin A1c test
  • HbA1c
  • Glycohemoglobin

This test can more accurately measure the amount of blood sugar over time, rather than simply measuring the blood sugar levels at the time of the test, as some other blood sugar tests do.

Although the glycated hemoglobin test is the new standard in diabetes diagnosis, it is not always used. There are some conditions that make the results inaccurate. Please talk with your doctor about what can affect the test results. In this case, doctors may use the following tests.

  • Random blood sugar test—this test can be taken at any time, regardless of when you last ate.
  • Fasting blood sugar test—this test must be taken after you have fasted (not eaten anything) overnight. It is usually performed in the morning after you have not eaten since the night before.

Tests for Gestational Diabetes

Screening for gestational diabetes is, for most healthcare providers, a routine part of prenatal care. The most common test used is called a glucose challenge test. It is recommended that the test be performed between the 24th and 28th week of pregnancy. If the patient is at high risk for developing gestational diabetes, the test may be performed earlier in the pregnancy.

The test involves two separate occasions of drinking a glucose solution and following with blood tests. The first test is done without fasting, and the second test is done after an overnight fast.

Tests for Prediabetes

Testing for prediabetes is the same as testing for Type 1 and Type 2 diabetes. Ask your doctor if you are at risk for prediabetes.


If you would like to schedule an appointment with an endocrinologist at Northwestern Memorial Hospital, you may call the Physician Referral Service at 1-877-926-4664 or request a first time appointment online. 

Last UpdateAugust 4, 2011


To make an appointment with a physician, please call 1-877-926-4664.

New patients can request an appointment online.