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Tests and diagnosis

By Mayo Clinic staff

In June 2009, an international committee composed of experts from the American Diabetes Association, the European Association for the Study of Diabetes and the International Diabetes Federation recommended that type 1 diabetes testing include the:

  • Glycated hemoglobin (A1C) test. This blood test indicates your average blood sugar level for the past two to three months. It works by measuring the percentage of blood sugar attached to hemoglobin, the oxygen-carrying protein in red blood cells. The higher your blood sugar levels, the more hemoglobin you'll have with sugar attached. An A1C level of 6.5 percent or higher on two separate tests indicates you have diabetes. A result between 6 and 6.5 percent is considered prediabetes, which indicates a high risk of developing diabetes.

If the A1C test isn't available, or if you have certain conditions that can make the A1C test inaccurate — such as if you're pregnant or have an uncommon form of hemoglobin (known as a hemoglobin variant) — your doctor may use the following tests to diagnose diabetes:

  • Random blood sugar test. A blood sample will be taken at a random time. Blood sugar values are expressed in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). Regardless of when you last ate, a random blood sugar level of 200 mg/dL (11.1 mmol/L) or higher suggests diabetes, especially when coupled with any of the signs and symptoms of diabetes, such as frequent urination and extreme thirst.
  • Fasting blood sugar test. A blood sample will be taken after an overnight fast. A fasting blood sugar level less than 100 mg/dL (5.6 mmol/L) is normal. A fasting blood sugar level from 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is considered prediabetes. If it's 126 mg/dL (7 mmol/L) or higher on two separate tests, you have diabetes.

If you're diagnosed with diabetes, your doctor will also run blood tests to check for autoantibodies that are common in type 1 diabetes. These tests help your doctor distinguish between type 1 and type 2 diabetes. The presence of ketones — byproducts from the breakdown of fat — in your urine also suggests type 1 diabetes, rather than type 2.

After the diagnosis
Once you've been diagnosed with type 1 diabetes, you'll regularly visit your doctor to ensure good diabetes management. During these visits, the doctor will also check your A1C levels. Your target A1C goal may vary depending on your age and various other factors, but the American Diabetes Association generally recommends that A1C levels be below 7 percent, which translates to an estimated average glucose of 154 mg/dL (8.5 mmol/L).

Compared with repeated daily blood sugar tests, A1C testing better indicates how well your diabetes treatment plan is working. An elevated A1C level may signal the need for a change in your insulin regimen or meal plan.

In addition to the A1C test, the doctor will also take blood and urine samples periodically to check your cholesterol levels, thyroid function, liver function and kidney function and to test for celiac disease. The doctor will also examine you to assess your blood pressure, and he or she will check the sites where you test your blood sugar and deliver insulin.

Treatments and drugs Preparing for your appointment
References
  1. Diabetes Mellitus (DM). The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec12/ch158/ch158b.html#sec12-ch158-ch158b-1105. Accessed April 2, 2009.
  2. Standards of medical care in diabetes — 2009. Alexandria, Va.: American Diabetes Association. http://care.diabetesjournals.org/cgi/reprint/32/Supplement_1/S13. Accessed April 1, 2009.
  3. Eisenbarth GS, et al. Pathogenesis of type 1 diabetes mellitus. http://www.uptodate.com/home.index.html. Accessed Jan. 5, 2009.
  4. Gillespie KM. Type 1 diabetes: Pathogenesis and prevention. Canadian Medical Association Journal. 2006;175. http://www.mdconsult.com/das/article/body/115743848-3/jorg=journal&source=MI&sp=163/jorg=journal&source=MI&sp=16. Accessed Jan. 6, 2009.
  5. Heart disease and stroke statistics — 2009 update. American Heart Association. http://www.americanheart.org/downloadable/heart/123565990943909Heart%20and%20Stroke%20Update.pdf. Accessed April 1, 2009.
  6. Your guide to diabetes: Type 1 and type 2. National Institute of Diabetes and Digestive and Kidney Diseases. http://diabetes.niddk.nih.gov/dm/pubs/type1and2/index.htm. Accessed April 1, 2009.
  7. What people with diabetes need to know about osteoporosis. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Accessed Jan. 9, 2009.
  8. Jovanavic L. Successful pregnancy in women with type 1 diabetes: From preconception through postpartum care. Endocrinology and Metabolism Clinics of North America. 2006;35:79.
  9. Bainbridge KE. Diabetes and hearing impairment in the United States: Audiometric evidence from the National Health and Nutrition Examination Survey, 1999 to 2004. Annals of Internal Medicine. 2008;149:1.
  10. Estimated average glucose, eAG. American Diabetes Association. http://professional.diabetes.org/GlucoseCalculator.aspx. Accessed Jan. 6, 2009.
  11. Pfizer statement on Exubera labeling update in the United States. Pfizer.com. Accessed April 3, 2009.
  12. About omnipod. Omnipod.com. http://www.myomnipod.com/products/. Accessed April 3, 2009.
  13. Symlin (prescribing information). San Diego, Calif.: Amylin Pharmaceuticals; 2008.
  14. Diabetes and women's sexual health. American Diabetes Association. http://www.diabetes.org/type-1-diabetes/women-sexual-health.jsp. Accessed April 3, 2009.
  15. Hypoglycemia. National Institute of Diabetes and Digestive and Kidney Diseases. http://diabetes.niddk.nih.gov/dm/pubs/hypoglycemia/index.htm. Accessed April 2, 2009.
  16. Diabetes and employment. Alexandria, Va.: American Diabetes Association. http://care.diabetesjournals.org/cgi/content/full/32/Supplement_1/S80. Accessed April 1, 2009.
  17. Robertson RP. Pancreas and islet transplantation in diabetes mellitus. http://www.uptodate.com/home.index.html. Accessed Jan. 6, 2009.
  18. Voltarelli J, et al. Autologous nonmyeloablative hematopoietic stem cell transplantation in newly diagnosed type 1 diabetes mellitus. Journal of the American Medical Association. 2007;297:1568.
  19. Havas S, et al. Tight control of type 1 diabetes: Recommendations for patients. American Family Physician. 2006;74:971.
  20. The dangerous toll of diabetes. American Diabetes Association. http://www.diabetes.org/diabetes-statistics/dangerous-toll.jsp. Accessed April 3, 2009.
  21. High blood sugar: Definition, symptoms. Juvenile Diabetes Research Foundation. http://www.jdrf.org/index.cfm?fuseaction=home.viewpage&page_id=EC92D98E-1321-C844-13EB771367A49526. Accessed April 3, 2009.
  22. Smoking. American Diabetes Association. http://www.diabetes.org/type-1-diabetes/smoking.jsp. Accessed April 3, 2009.
  23. TrialNet studies. TrialNet. http://www.diabetestrialnet.org/patientinfo/studies.htm. Accessed April 3, 2009.
  24. Collazo-Clavell ML (expert opinion). Mayo Clinic. Rochester, Minn. April 14, 2009.
  25. International Expert Committee. International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care. 2009;32:1.

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June 13, 2009

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