In 2007, approximately 23.6 million Americans had diabetes, according to Umesh Masharani, M.B., Professor of Medicine at the University of California in "Current Medical Diagnosis & Treatment." Insulin moves glucose out of the blood and into the tissues and cells. People with diabetes have high levels of glucose in their bloodstreams. In diabetes type 1, an autoimmune process destroys the pancreatic cells that release insulin. In type 2, the tissues and cells do not respond to insulin. Pregnant women who never had diabetes, but have high glucose levels during pregnancy are said to have gestational diabetes. There are several tests used to diagnose diabetes.
Plasma Glucose Levels
Normal glucose levels are 60 to 110 mg/dL. As explained by Ernesto Bernal-Mizrachi, M.D. in "The Washington Manual of Medical Therapeutics," people are diagnosed with diabetes mellitus, if the results of a random glucose test are over 200 mg/dL and they have the symptoms of the disease. The symptoms would include drinking a lot of fluids and frequent urination. An alternative test to diagnose diabetes is to check the fasting plasma glucose levels. This involves checking the levels of glucose in the bloodstream after fasting, or after not having any food for eight hours. If the fasting levels are over 126 mg/dL on two different occasions, then this is also a positive result for diabetes.
Glucose Tolerance Test (GTT)
This is another test that can be used to diagnose diabetes. Diana Nicoll, M.D., Ph.D. explains the test in the "Pocket Guide to Diagnostic Tests." First the lab takes the fasting glucose level. Then people drink 75 g of glucose, which has been dissolved in water. One hour later, the glucose level is taken, and then taken yet again in another hour. In a normal result, the fasting level is less than 100 mg/dL, less than 200 mg/dL after the first hour, and below 140 mg/dL after two hours.
GTT in Pregnancy
All pregnant women take the glucose tolerance test to screen for diabetes when they are between 24 to 28 weeks. No fasting glucose level is needed and instead of 75 grams of glucose, they drink 50 grams. If they have an abnormal result, then they have another glucose tolerance test. For this one, the lab will first need a fasting level. Then the women drink 100 grams of glucose. The lab will check their blood glucose levels in one hour, two hours and three hours. A normal fasting level is below 105 mg/dL. A normal one-hour level is less than 190 mg/dL, the two-hour level should be less than 165 mg/dL and the three-hour level should be below 145 mg/dL.
Hemoglobin A1C
A red blood cell lives for 120 days. During that time, the hemoglobin in the red blood cell becomes bound, or attached, to glucose. Hemoglobin is the protein in the red blood cell that carries the oxygen. Hemoglobin A1C measures the amount of glucose bound to the hemoglobin in the red blood cells. It is a test to see if diabetics are controlling their diets and blood glucose levels because it reflects the glucose levels for the previous two to four months. Diabetics should have the goal of a hemoglobin A1C level below 7 percent, according to the Merck Manual.
References
- "Current Medical Diagnosis & Treatment 2010"; Stephen McPhee, M.D., Maxine Papadakis, M.D.; 2010
- "Pocket Guide to Diagnostic Tests"; Diana Nicoll, M.D., Ph.D., Stephen McPhee, M.D., Michael Pignone, M.D., Chuanyi Lu, M.D.; 2007
- The Merck Manual for Healthcare Professionals: Diabetes Mellitus (DM)
- "The Washington Manual of Medical Therapeutics"; Gopa Green, M.D., Ian Harris, M.D., Grace Lin, M.D., Kyle Moylan, M.D.; 2004
