Diagnosis and Treatment Protocols for Diabetes
Diagnostic Criteria
Diabetes is diagnosed using any one of four criteria: A1C ≥6.5%, fasting plasma glucose ≥126 mg/dL, 2-hour plasma glucose ≥200 mg/dL during 75-g OGTT, or random glucose ≥200 mg/dL with classic hyperglycemic symptoms (polyuria, polydipsia, unexplained weight loss) or hyperglycemic crisis. 1, 2
Confirmation Requirements
- In the absence of unequivocal hyperglycemia (such as hyperglycemic crisis), diagnosis requires two abnormal test results, either from the same sample or two different time points 1
- A1C must be performed using an NGSP-certified method standardized to the DCCT assay 1, 2
- Fasting is defined as no caloric intake for at least 8 hours 1, 2
- The 75-g OGTT should be performed as described by WHO 1
Classification After Diagnosis
Classifying diabetes type at diagnosis is critical because it fundamentally determines treatment approach—Type 1 requires immediate insulin, while Type 2 may initially respond to non-insulin therapies. 1
Type 1 Diabetes
Diagnostic Features
- Accounts for approximately 5% of diagnosed diabetes cases and is defined by autoimmune β-cell destruction with presence of one or more autoimmune markers 1
- Children typically present with polyuria/polydipsia, and approximately one-third to one-half present with diabetic ketoacidosis 1
- Adults may have more variable presentation without classic symptoms seen in children and may experience temporary remission from insulin need 1
- Islet autoantibodies (GAD, IA-2, ZnT8, insulin antibodies) are present in 85-90% of individuals at diagnosis 1
Diagnostic Algorithm for Adults
When Type 1 diabetes is suspected in adults, test islet autoantibodies first (GAD as primary, followed by IA-2 and/or ZnT8 if negative). 1
- If autoantibody positive: Confirms Type 1 diabetes 1
- If autoantibody negative in patients <35 years without features of Type 2 or monogenic diabetes: Still likely Type 1 diabetes (5-10% of adult-onset Type 1 is autoantibody negative) 1
- If autoantibody negative with unclear classification: Test C-peptide after >3 years duration; <200 pmol/L confirms Type 1 1
Treatment Protocol
Type 1 diabetes requires immediate insulin therapy because there is absolute insulin deficiency from β-cell destruction. 1, 3
Insulin Regimen
- Most patients should use intensive insulin regimens: either multiple daily injections (3-4 injections of basal and prandial insulin per day) or continuous subcutaneous insulin infusion (insulin pump) 1
- Basal insulin (glargine, detemir, degludec) provides background 24-hour coverage; initiate at 10 units or 0.1-0.2 units/kg body weight 2, 4
- Rapid-acting insulins (lispro, aspart, glulisine) are administered immediately before meals with onset within 15 minutes, peak at 1-2 hours, and duration of 3-5 hours 2
Monitoring
- Self-monitoring of blood glucose should be performed before meals and snacks, occasionally postprandially, at bedtime, before exercise, when hypoglycemia is suspected, and before critical tasks such as driving 1
- Continuous glucose monitoring may be useful adjunct to self-monitoring in patients on intensive insulin regimens 1
Type 2 Diabetes
Diagnostic Features
- Results from progressive loss of adequate β-cell insulin secretion on the background of insulin resistance 1
- Traditional paradigm of Type 2 occurring only in adults is no longer accurate; occurs in all age groups 1
- Occasionally may present with diabetic ketoacidosis, particularly in ethnic and racial minorities 1
Treatment Protocol
Treatment of Type 2 diabetes is more complex than Type 1 because defects exist in both insulin secretion and insulin action, requiring treatment selection based on disease stage and individual characteristics. 3
Initial Management
- Lifestyle intervention including dietary counseling, exercise regimens, patient education, and self-administered blood glucose monitoring demonstrates promising results 5
- Early intervention and treatment of at-risk patients are critical for positive outcomes 5
Pharmacologic Treatment
- Treatment selection depends on stage of disease and individual patient characteristics 3
- When insulin is required, basal insulin is initiated at 10 units or 0.1-0.2 units/kg body weight and titrated based on fasting glucose readings 2
- Long-acting insulins (glargine, detemir, degludec) provide relatively peakless coverage over 24 hours 2, 4, 6
Monitoring
- Frequency and timing of self-monitoring should be dictated by specific treatments, needs, and goals 1
- Evidence is insufficient to determine optimal frequency for patients not on intensive insulin regimens, but performing self-monitoring alone does not decrease blood glucose—information must be integrated into clinical and self-management plans 1
Gestational Diabetes Mellitus (GDM)
Screening Protocol
Screen all pregnant women at 24-28 weeks gestation for gestational diabetes using either the "1-step" strategy with 75-g OGTT or "2-step" approach with 50-g nonfasting screen followed by 100-g OGTT for those who screen positive. 1, 2
Early Pregnancy Screening
- Women with risk factors should be tested for undiagnosed Type 2 diabetes at first prenatal visit using standard diagnostic criteria 1
- Before 15 weeks gestation, screen for early abnormal glucose metabolism using fasting glucose 110-125 mg/dL or A1C 5.9-6.4% to identify those at higher risk of adverse outcomes 1
Treatment Protocol
- Lifestyle intervention including dietary counseling, exercise, patient education, and self-administered blood glucose monitoring 5
- When drug treatment is needed, insulin and insulin analogs have shown efficacy in achieving glycemic control and improving maternal and neonatal outcomes 5
- Continuous glucose monitoring and telemedicine have become valuable tools in managing diabetes during pregnancy 5
Postpartum Management
Women with gestational diabetes should be screened for persistent diabetes at 4-12 weeks postpartum using 75-g OGTT and clinically appropriate non-pregnancy diagnostic criteria. 1
- Women with history of GDM should have lifelong screening for diabetes or prediabetes at least every 3 years 1
- Type 1 diabetes develops in 5.7% during first 7 years after GDM pregnancy and is predictable at 2-hour OGTT value of 11.9 mmol/l during pregnancy 7
- Type 2 diabetes increases linearly to 50.4% by end of follow-up and is moderately predictable with fasting glucose at 5.1 mmol/l 7
Special Diabetes Types
Maturity-Onset Diabetes of the Young (MODY)
Consider MODY in patients with mild stable fasting hyperglycemia (100-150 mg/dL), stable A1C between 5.6-7.6%, multiple family members with diabetes not typical of Type 1 or Type 2, and absence of obesity. 1
- All children diagnosed with diabetes in first 6 months of life should have genetic testing 1
- Genetic testing is cost-effective and increasingly supported by health insurance 1
- Correct diagnosis is critical because misdiagnosis as Type 1 or Type 2 leads to suboptimal, potentially harmful treatment 1
Drug-Induced Diabetes
Certain medications increase diabetes risk: glucocorticoids, thiazide diuretics, and atypical antipsychotics. 1
Critical Safety Considerations
Hypoglycemia Management
- Hypoglycemia may be life-threatening; increase frequency of glucose monitoring with changes to insulin dosage, concomitant drugs, meal pattern, physical activity, and in patients with renal or hepatic impairment 4
- Early warning symptoms may be reduced or absent with long diabetes duration, diabetic neuropathy, beta-blocker use, or intensified control 6
- Antiadrenergic drugs (beta-blockers, clonidine, guanethidine, reserpine) may reduce or eliminate signs and symptoms of hypoglycemia 4, 6
Medication Errors
- Accidental mix-ups between insulin products can occur; instruct patients to check insulin labels before every injection 4
- Never share insulin pens, syringes, or needles between patients, even if needle is changed 4
Insulin Mixing
- Long-acting insulins (glargine, detemir) should NOT be mixed or diluted with any other insulin preparations 4, 6
- Mixing can alter the action profile of one or both components 6
Other Warnings
- Hypokalemia may be life-threatening; monitor potassium levels in at-risk patients 4
- With concomitant thiazolidinedione use, observe for signs of heart failure; consider TZD dosage reduction or discontinuation if heart failure occurs 4
- Lipodystrophy may occur at injection sites; continuous rotation within given area helps reduce this risk 4, 6