Connect with others who've been there. Share stories. Learn. Join Mayo Clinic's
online community.

Free

E-Newsletters

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

  • Housecall
  • Alzheimer's caregiving
  • Living with cancer
View the Mayo Diet Book

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 2 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. Normal levels are below 5.7 percent.

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. A blood sugar level less than 140 mg/dL (7.8 mmol/L) is normal.
  • 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 mellitus. From 100 mg/dL (5.6 mmol/L) to 125 mg/dL (6.9 mmol/L) is considered prediabetes, which puts you at greater risk of developing diabetes.
  • Oral glucose tolerance test. For this test, you fast overnight, and the fasting blood sugar level is measured. Then you drink a sugary liquid, and blood sugar levels are tested periodically for the next several hours. A blood sugar level less than 140 mg/dL (7.8 mmol/L) is normal. A reading of more than 200 mg/dL (11.1 mmol/L) after two hours indicates diabetes. A reading between 140 and 199 mg/dL (7.8 mmol/L and 11.0 mmol/L) indicates prediabetes.

The American Diabetes Association recommends routine screening for type 2 diabetes beginning at age 45, especially if you're overweight. If the results are normal, repeat the test every three years. If the results are borderline, ask your doctor when to come back for another test. Screening is also recommended for people who are under 45 and overweight if there are other heart disease or diabetes risk factors present, such as a sedentary lifestyle, a family history of type 2 diabetes, a personal history of gestational diabetes or blood pressure above 135/80 millimeters of mercury (mm Hg).

If you're diagnosed with diabetes, the doctor may do other tests to distinguish between type 1 and type 2 diabetes — which often require different treatment strategies because in type 1 diabetes, the pancreas no longer makes insulin.

After the diagnosis
A1C levels need to be checked between two and four times a year. Your target A1C goal may vary depending on your age and various other factors. However, for most people, the American Diabetes Association recommends an A1C level below 7 percent. Ask your doctor what your A1C target is.

The American Diabetes Association has a formula that translates the A1C into what's known as an estimated average glucose (eAG). The eAG more closely correlates with daily blood sugar readings. An A1C of 7 percent translates to an eAG 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 medication 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. The doctor will assess your blood pressure. Regular eye and foot exams also are important.

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. McCulloch DK, et al. Risk factors for type 2 diabetes mellitus. http://www.uptodate.com/home/index.html. Accessed Feb. 18, 2011.
  4. 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.
  5. McCulloch DK. Initial management of blood glucose in type 2 diabetes mellitus. http://www.uptodate.com/home/index.html. Accessed Feb. 18, 2011.
  6. McCulloch DK, et al. Prediction and prevention of type 2 diabetes mellitus. http://www.uptodate.com/home/index.html. Accessed Feb. 18, 2011.
  7. Screening for type 2 diabetes mellitus in adults. U.S. Preventive Services Task Force. http://www.uspreventiveservicestaskforce.org/uspstf08/type2/type2rs.htm. Accessed Feb. 27, 2011.
  8. Diabetes statistics. American Diabetes Association. http://www.diabetes.org/diabetes-basics/diabetes-statistics. Accessed Feb. 27, 2011.
  9. 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.
  10. Helzner EP, et al. Contribution of vascular risk factors to the progression in Alzheimer disease. Archives of Neurology. 2009;66:343.
  11. 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.
  12. Baker WL, et al. Effect of cinnamon on glucose control and lipid parameters. Diabetes Care. 2008;31:41.
  13. Balk EM, et al. Effect of chromium supplementation on glucose metabolism and lipids. 2007;30:2154.
  14. Huxley R, et al. Coffee, decaffeinated coffee, and tea consumption in relation to incident type 2 diabetes mellitus. Archives of Internal Medicine. 2009;169:2053.
  15. Hyperosmolar hyperglycemic nonketotic syndrome (HHNS). American Diabetes Association. http://www.diabetes.org/living-with-diabetes/complications/hyperosmolar-hyperglycemic.html. Accessed Feb. 27, 2011.
  16. Diabetic ketoacidosis. National Center for Biotechnology Information. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001363. Accessed Feb. 24, 2011.
  17. Frye RL, et al. A randomized trial of therapies for type 2 diabetes and coronary artery disease. New England Journal of Medicine. 2009;360:2503.
  18. 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.
DS00585 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.

  • Reprints
  • Print

  • Share on:

  • Email

Advertisement


Text Size: smaller largerlarger