View the Health Heart Book

Free

E-Newsletters

Subscribe to receive the latest updates on health topics. About our newsletters

  • Housecall
  • Alzheimer's caregiving
  • Living with cancer
Connect with others who've been there. Share stories. Learn. Join Mayo Clinic's
online community.

Tests and diagnosis

By Mayo Clinic staff

In June 2009, an international committee 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 5.7 and 6.4 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. A level between 140 mg/dL (7.8 mmol/L) and 199 mg/dL (11.0 mmol/L) is considered prediabetes, which puts you at greater risk of developing diabetes.
  • 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. A level from 100 mg/dL (5.6 mmol/L) to 125 mg/dL (6.9 mmol/L) is considered prediabetes.

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 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 Feb. 22, 2011.
  2. Standards of medical care in diabetes — 2011. Diabetes Care. 2011:34:S11.
  3. Eisenbarth GS, et al. Pathogenesis of type 1 diabetes mellitus. http://www.uptodate.com/home.index.html. Accessed Feb. 18, 2011.
  4. Heart disease and stroke statistics — 2009 update. American Heart Association. http://www.americanheart.org/downloadable/heart/123565990943909Heart%20and%20Stroke%20Update.pdf. Accessed Feb. 22, 2011.
  5. Roberts AW. Cardiovascular risk and prevention in diabetes mellitus. Clinical Medicine. 2010;10:495.
  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 Feb. 22, 2011.
  7. What people with diabetes need to know about osteoporosis. National Institute of Arthritis and Musculoskeletal and Skin Diseases. http://www.niams.nih.gov/Health_Info/Bone/Osteoporosis/Conditions_Behaviors/diabetes.asp. Accessed Feb. 22, 2011.
  8. Bergenstal RM, et al. Effectiveness of sensor-augmented insulin pump therapy in type 1 diabetes. New England Journal of Medicine. 2010;363:311.
  9. Wahabi HA, et al. Preconception care for diabetic women for improving maternal and fetal outcomes: A systematic review and meta-analysis. BMC Pregnancy and Childbirth. 2010;10:63.
  10. Tieu J, et al. Preconception care for diabetic women for improving maternal and infant health (review). The Cochrane Collection. 2010;12.
  11. Robertson RP. Pancreas and islet transplantation in diabetes mellitus. http://www.uptodate.com/home.index.html. Accessed Feb. 22, 2011.
  12. Stem cell information. National Institutes of Health. http://stemcells.nih.gov/info/scireport/chapter7.asp. Accessed Feb. 24, 2011.
  13. National diabetes statistics, 2011. National Diabetes Information Clearinghouse. diabetes.niddk.nih.gov/DM/PUBS/statistics/DM_Statistics.pdf. Accessed Feb. 24. 2011.
  14. Hypoglycemia. National Institute of Diabetes and Digestive and Kidney Diseases. http://diabetes.niddk.nih.gov/dm/pubs/hypoglycemia/index.htm. Accessed Feb. 22, 2011.
  15. Diabetic ketoacidosis. National Center for Biotechnology Information. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001363. Accessed Feb. 24, 2011.
  16. Centers for Disease Control and Prevention, et al. Use of hepatitis B vaccine for adults with diabetes mellitus: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recommendations and Reports. 2011:60;1709.
DS00329 Jan. 25, 2012

© 1998-2012 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "EmbodyHealth," "Enhance your life," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research.

Print Share Reprints

Advertisement


Text Size: smaller largerlarger