Diabetes Mellitus


The student will be able to diagnose, classify, and manage diabetes mellitus in a clinic setting.



Type 1 Diabetes
Type 2 Diabetes
  • ranges from predominantly insulin resistant with relative insulin deficiency to predominantly an insulin secretory defect with insulin resistance.
  • previously called non-insulin-dependent diabetes mellitus (NIDDM) or adult-onset diabetes.
  • autosomal dominant inheritance pattern is present.
  • 80% to 90% of these patients are obese.
  • 90% of diabetics in the United States are Type 2.
    Table 1. Diagnosing Diabetes
    STAGE  Fasting Plasma Glucose (FPG)(Preferred)* 
    Casual Plasma Glucose 

    Oral Glucose Tolerance Test (OGTT) 
    Diabetes  FPG 126 mg/dL (7.0 mmol/L)**  Casual plasma glucose 200 mg/dL (11.1 mmol/L) plus symptoms***  Two-hour plasma glucose (2hPG) 200 mg/dL**** 
    Impaired Glucose Homeostasis  Impaired fasting glucose (IFG) = FPG 110 and < 126 g/dL    Impaired glucose tolerance (IGT) = 2hPG > 140 and < 200 mg/dL 
    Normal FPG < 110 mg/dL    2hPG < 140 mg/dL 

    * The FPG is the preferred test for diagnosis, but any 1 of the 3 listed is acceptable. In the absence of unequivocal hyperglycemia with acute metabolic decompensation, 1 of these 3 tests should be used on a different day to confirm diagnosis.
    ** Fasting is defined as no caloric intake for at least 8 hours.
    *** Casual = any time of day without regard to time since last meal; symptoms are the classic ones of polyuria, polydipsia, and unexplained weight loss.
    **** OGTT should be performed using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water. The OGTT is not recommended for routine clinical use.

    From: Rayburn WE. Clinical perspectives: Diagnosis and classification of diabetes mellitus: Highlights from the American Diabetes Association. J Reprod Med 0024-7758/97/4209-0585.

    Table 2. Criteria for Testing in Asymptomatic Undiagnosed Individuals
    Type 1 Diabetes: Testing presumably healthy individuals for the presence of any immune markers, outside of a clinical trials setting, is not recommended. 

    Type 2 Diabetes: In asymptomatic, undiagnosed individuals, testing for diabetes should be considered in all individuals at age 45 and above, and, if normal, it should be repeated at 3-year intervals. 

    Testing should be considered at a younger age, or be carried out more frequently, in individuals who: 

    • are obese [ 120% desirable body weight or a body mass index (BMI) 27 kg/m2
    • have a first-degree relative with diabetes are members of a high-risk ethnic population (African American, Hispanic, Native American, Asian) 
    • delivered a baby weighing >9 lbs or were diagnosed with GDM 
    • are hypertensive ( 140/90 mm Hg) 
    • have an HDL cholesterol level 35 mg/dL and/or a triglyceride level 250 mg/dL 
    • on previous testing, had IGT or IFG. 
    • The FPG is the preferred diagnostic test because of its ease of administration, convenience, acceptability to patients, and lower cost. 
    (adapted from Diabetes Care, July 1997;20(7): 11.) 


    Impaired Glucose Tolerance (IGT) and Impaired Fasting Glucose (IFG)
  • Patients with IGT respond abnormally to the glucose tolerance test, but do not meet the criteria required to diagnose diabetes.
  • Patients with IFG have abnormal fasting glucose, but are not diagnostic for D.M. and have normal glucose tolerance tests.
  • IGT and IFG are not clinical entities, but are risk factors for future D.M. and cardiovascular disease.

    Diagnostic Criteria and Screening
    (refer to Tables 1 and 2)

    HbA1c measurement is not currently recommended for diagnosis of D.M.


    Outpatient Management

    Goals of Therapy

    (refer to Table 3)

    Methods of Therapy


    The cornerstone of therapy for all obese diabetics is a weight-reduction diet. This is especially true of the obese Type 2 diabetic. The primary emphasis is a reduction in total calories in order to effect a weight loss. This often requires a diet limiting daily intake to 1200 calories or less. Even a relatively small amount of weight loss usually achieves control (85% of patients), and continued, gradual weight loss will maintain control in the obese, Type 2 diabetic. Without weight loss in these patients, good control of the diabetes is very difficult to achieve.

    The type of calories and timing of the meals is more important in the non-obese diabetic on insulin.

    Increased fiber content may be of benefit.

    A dietitian should be consulted for instruction and on-going supervision of the diabetic patient.


    Adequate physical activity has been shown to increase insulin receptor sites and lower insulin requirements. A regular exercise program should be prescribed.

    Table 3. Glycemic Control for People with Diabetes*
    Biochemical Index Nondiabetic  Goal Additional Action Suggested 
    Preprandial glucose (mg/dL)**  < 110 80-120  < 80 

    > 140 

    Bedtime glucose (mg/dL)**  < 120 100-140 < 100 

    > 160 

    HbA1c (%) < 6  < 7  > 8 
    * The values shown in this table are by necessity generalized to the entire population of individuals with diabetes. Patients with comorbid diseases, the very young and older adults, and others with unusual conditions or circumstances may warrant different treatment goals. These values are for nonpregnant adults. "Additional action suggested" depends on individual patient circumstances. Such actions may include enhanced diabetes self-management education, comanagement with a diabetes team, referral to an endocrinologist, change in pharmacological therapy, initiation of or increase in SMBG, or more frequent contact with the patient. HbA1c is referenced to a nondiabetic range of 4.0-6.0% (mean 5.0%, SD 0.5%). 
    ** Measurement of capillary blood glucose. 
    American Diabetes Association. Standards of medical care for patients with diabetes mellitus. Diabetes Care, January 1998;21(Suppl. 1):S23-S31.

    Oral Hypoglycemic Agents

    Sulfonylureas may be used in Type 2 diabetics over 30 who have failed diet therapy, or as an adjunct while diet and exercise are being instituted. They are more likely to be effective in patients with mildly elevated glucose (FBS <300).

    The second generation agents glyburide and glipizide are more potent and may be attempted in patients with marked hyperglycemia or who failed the first generation agents.

    Sulfonylureas cannot be used during pregnancy and are contraindicated in patients with hepatic or renal dysfunction. Because of its long duration of action, glyburide should be avoided in elderly patients.

    Metformin (Glucophage) is a new oral hypoglycemic agent that may be
    used alone or in combination with a sulfonylurea agent. Combination therapy may delay or avoid insulin therapy when treatment with one oral agent has failed. Metformin is contraindicated in patients with renal dysfunction (serum creatinine 1.5 in men and 1.4 in women). Also avoid metformin in patients who have a history of binge drinking and those prone to dehydration.

    Troglitazone (Rezulin) improves sensitivity to insulin in muscle and adipose tissue and inhibits hepatic gluconeogenesis. It can be used as monotherapy or in combination with other oral agents or insulin. It has synergistic effects with sulfonylureas. When added to insulin, the dose of insulin can usually be lowered approximately 50%. Disadvantages include high cost and potential hepatic injury. Monitoring LFTs is required.

    Table 4. Sulfonylureas* 
    Drug  Tablet Size Daily Dose  Duration of 


    Tolbutamide (Orinase)  250 mg and500 mg  0.5-2 g in 2 or 3 divided doses  6-12 hours 
    Tolazamide(Tolinase)  100 mg, 250 mg, and 500 mg  0.1-l g as single dose or in 3 divided doses Up to 24 hrs. 
    Glyburide (Diabeta, Micronase)  1.25 mg, 2.5 mg, and 5 mg doses  1.25-20 mg as single dose or in 2 divided Up to 24 hrs. 
    Glipizide(Glucotrol)  5 mg and 10 mg 2.5-30 mg as single dose or in 2 or 3 divided doses on an empty stomach  6-12 hours 
    * All are available in generic. 
    Table 5. A Suggested Algorithm for Insulin Dosage Adjustment Based on Blood Glucose Determinations (blood, plasma, or serum)*
    Initial doses:
    Team Approach. Members of the team include nurses for patient education and support groups, dietitions as mentioned above, physical therapists or podiatrists for on-going foot care, ophthalmologists for periodic exams to detect retinal changes at a treatable stage, and nephrologists when advanced renal impairment occurs.

    Visits to ophthalmologists should occur annually. Retinal photography is indicated for any newly diagnosed diabetic, any Type 1 diabetic of 5 years or more, and all Type 2 diabetics.

    A foot examination should be performed on each visit to detect early foot problems and to emphasize good foot care.

    Urinalysis should be performed annually to detect proteinuria. Analysis for microalbuminuria can detect proteinuria at an earlier stage. Begin ACE inhibitor if proteinuria is detected.

    American Diabetes Association. Standards of medical care for patients with diabetes mellitus. Diabetes Care, January 1998;21(Suppl 1):S23-S31.

    Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care, January 1998;21(Suppl. 1):S5-S19.

    American Diabetes Association: Clinical Practice Recommendations 2000; Volume 23 Supplement 1, January 2000


    M. Harper, MD
    updated 8/30/05

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