The doctor will ask about your symptoms, and medical and family history. A physical exam will be done. There are 4 main tests used to diagnose diabetes. Most tests results should be confirmed with repeat testing. The American Diabetes Association (ADA) recommends using one of the following tests to make the diagnosis:
You will need to avoid eating for at least 8 hours before the test. A sample of your blood will be taken. The blood glucose level will be measured. A measure of 126 milligrams per deciliter (mg/dl) (7 millimole per liter of blood [mmol/L]) or higher indicates a diagnosis of diabetes.
Symptoms typical of diabetes include excessive thirst and hunger, frequent urination, and weight loss. Your doctor will make the diagnosis based on your symptoms and the results of the random plasma glucose test. This test is taken any time of day (without regard to when you have last eaten). A sample of your blood will be taken. The blood glucose level will be measured. A measure of 200 (mg/dl) [11.1 mmol/L] or higher along with typical symptoms indicates the presence of diabetes.
This starts with a 3-day intake of a diet consisting of at least 150 grams of carbohydrates. You will then be asked to fast overnight (between 8-16 hours). The test is generally done in the morning, in your doctor's office.
A blood sample will be obtained from you to measure the blood sugar level. Then, you will drink 75 grams of glucose dissolved in water. Two hours later, another blood sample will be obtained to measure the blood sugar level. If you have diabetes, your blood sugar level will rise higher than normal and remain high for a much longer time than is normal. A measure of 200 mg/dl (11.1 mmol/L) or higher at 2 hours is considered a positive test.
The HbA1c test is a good indicator of your average blood sugar levels over the previous 2-4 months. This test usually does not require any dietary restrictions. A blood sample will be taken. If your HbA1c level is 6.5% or higher, this indicates a diagnosis of diabetes.
After the diagnosis of diabetes is confirmed, your doctor will most likely order the following tests:
Diabetes mellitus type 2. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated July 29, 2013. Accessed August 28, 2013.
Diagnosis of diabetes and prediabetes. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: http://www.niddk.nih.gov/health-information/health-topics/Diabetes/diagnosis-diabetes-prediabetes/Pages/index.aspx. Updated August 29, 2012. Accessed August 28, 2013.
Glycemic control monitoring. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated May 20, 2013. Accessed August 28, 2013.
Rosenbloom AL, Silverstein JH, Amemiya S, et al. ISPAD clinical practice consensus guideline 2006-2007. Type 2 diabetes mellitus in the child and adolescent. Pediatr Diabetes. 2008;9(5):512-526.
Rosenzweig JL, Ferrannini E, Grundy SM, et al. Primary prevention of cardiovascular disease and type 2 diabetes in patients at metabolic risk: an endocrine society clinical practice guideline. J Clin Endocrinol Metab. 2008;93(10):3671-3689.
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2/15/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: American Diabetes Association. Standards of medical care in diabetes—2010. Diabetes Care. 2010;33 Suppl 1:S11-S61.
2/15/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2010;33 Suppl 1:S62-S69.
Last reviewed September 2015 by Kim A. Carmichael, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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