Diabetes Type 2: Nothing Sweet About ItPage 8 of 16

6. Diagnosing Diabetes Mellitus

Signs and Symptoms of T2DM

Diabetes is diagnosed by documenting hyperglycemia through blood tests. In addition to blood tests, the initial examination of a patient suspected of having diabetes includes a history and physical examination that looks for signs of disease.

Clinical Presentation

Three symptoms—polyuria, polydipsia, and weight loss—have defined diabetes for centuries. This description written one hundred years ago still applies:

The symptoms are usually gradual in their onset, and the patient may suffer for a length of time before he thinks it necessary to apply for medical aid. The first symptoms that attract attention are failure of strength, and emaciation, along with great thirst and an increased amount and frequent passage of urine. From the normal quantity of from 2 to 3 pints in the 24 hours it may be increased to 10, 20, or 30 pints, or even more. It is usually of pale colour, and of thicker consistence than normal urine, possesses a decidedly sweet taste, and is of high specific gravity. (Encyclopaedia Britannica, 1911)

In addition to the classic triad of polyuria, polydipsia, and weight loss, people with diabetes are often weak, frequently hungry between meals, may have blurred vision, and are prone to infections.

Hyperglycemia can present with vomiting, abdominal pain, dehydration, mental status changes, or coma (ADA, 2015). Many times people are newly diagnosed after presenting to an emergency department with acute symptoms that can mimic a flu.

Test Your Knowledge

The classic triad of symptoms of diabetes is:

  1. Gluconeogenesis, glycosuria, and glycolysis.
  2. Blurry vision, dehydration, and mental status changes.
  3. Macular edema, albuminuria, and seizures.
  4. Polyuria, polydipsia, and weight loss.

Apply Your knowledge

What causes the three classic symptoms of diabetes?

Online Resource


Answer: D

Medical History

The initial baseline workup of a patient with diabetes requires a review of illnesses, medications, family health history, lifestyle, and risk factors. The medical history should include:


Patient’s current symptoms and when they began

  • Results of any previous blood or urine glucose tests
  • History of any episodes of diabetic ketoacidosis or hypoglycemia
  • History of any diabetic complications:
    • Macrovascular (heart, arteries, stroke)
    • Microvascular (eyes, kidneys, nerves)
    • Infections or poor wound healing
    • Periodontal disease


History of all medicines currently taking


Any family history of diabetes


Level (to prepare for appropriate educational materials)

Physical Assessment

The initial physical examination focuses on signs of any health problems as well as developing diabetic complications. The exam includes:

  • Height, weight, and calculation of body mass index (BMI)
  • Blood pressure, including the blood pressure response to standing (orthostatic measurement) when autonomic dysfunction is suspected
  • Funduscopic eye exam
  • Skin exam for poorly healing injuries and signs of reduced circulation
  • Foot exam, including palpation of pulses and tests of fine sensation (proprioception, vibration, light touch) and reflexes using a monofilament and tuning fork (ADA, 2015)

Laboratory Test Results

Blood Glucose Tests

The patient’s blood glucose levels are used to diagnose and to monitor diabetes. Four glucose tests give a snapshot of a patient’s current ability to regulate blood glucose levels:

  • Fasting plasma glucose (FPG) is taken at least 8 hours after the patient has had any nourishment. Diabetes is characterized by an FPG >126 mg/dl.
  • Postprandial glucose level (PPG) is taken 1 to 2 hours after a meal. Diabetes is characterized by any random PPG >200 mg/dl with symptoms.
  • Oral glucose-tolerance test (OGTT) is a standardized postprandial glucose test. The OGTT is taken 2 hours after the patient has ingested 75g of oral glucose. Diabetes is characterized by an OGTT >200 mg/dl at the 2 hour time mark.
  • Glycosylated hemoglobin (A1c) measures the saturation of hemoglobin molecules over the life of a red blood cell, which is 3 months. The normal range is 4-6 mg/dL.
Source: Monnier et al., 2009.

A1c Values and Degree of Glycemic Control

A1c value

Degree of blycemic control


Near normal


Well controlled


Moderately controlled


Poorly controlled

In 2010 the American Diabetic Association adopted standards recommending the use of the A1c test to diagnose diabetes with a threshold set at 6.5%. The A1c test reflects the average glucose saturation over three months time and is strongly predictive of diabetic complications at higher levels.

The A1c has several advantages over the FPG and OGTT, including greater convenience because fasting is not required. A1c testing is recommended at the following intervals:

  • Twice a year to measure overall control of diabetes
  • Quarterly in the patient whose therapy has changed, or who is not meeting goals
  • As needed, using Point of Care testing to make timely decisions regarding change of therapy

Anemia and hemoglobinopathies, such as sickle cell disease, may distort true results of A1c testing if the red blood cells are impaired. For conditions with abnormal red blood cell turnover such as pregnancy, recent blood loss, and transfusion, the diagnosis of diabetes must use one of the other three tests instead of A1c. If symptoms have not been present for three months prior to diagnosis, an A1c may not be accurate as it represents the average of three months.

Other Blood Tests

To assess for diabetic complications, baseline values are needed for:

  • Fasting lipids (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides)
  • Liver function tests
  • Kidney function test (serum creatinine and glomerular filtration rate, GFR) (ADA, 2015)
Urine Tests
  • Urinalysis for albumin (ADA, 2015)
  • Urine for microalbumin (thought to be a more sensitive assay for albumin; an early indicator of diabetic nephropathy)