Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School



Diabetes is diagnosed by testing the blood for sugar levels. Blood is tested in the morning after you have fasted overnight.

Typically, the body keeps blood sugar levels between 70 and 100 milligrams per deciliter (mg/dL), even after fasting. If a blood sugar level after fasting is greater than 125 mg/dL, diabetes is diagnosed.

Your doctor will examine you to look for signs of diabetes complications. These include:

  • Obesity, especially abdominal obesity.

  • High blood pressure

  • Deposits of blood, or puffy yellow spots in the retina of your eyes

  • Decreased sensation in the legs

  • Weak pulses in the feet

  • Abnormal pulses in the abdomen

  • Blisters, ulcers or infections of the feet

Laboratory tests are also used routinely to evaluate diabetes. These include:

  • Fasting glucose. A test of your blood sugar level after you have not eaten for several hours.

  • Hemoglobin A1C (HbA1c). Indicates how close to average your blood glucose has been during the previous two months.

  • Blood creatinine and urine microalbumin. Tests for evidence of kidney disease.

  • Lipid profile. Measures levels of triglycerides and total, HDL, and LDL cholesterol. This evaluates the risk of atherosclerosis.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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