What is the recommended workup and initial management for a suspected case of type one diabetes in a child or young adult with symptoms like polyuria, polydipsia, and weight loss?

Workup for Type 1 Diabetes

In a child or young adult presenting with classic symptoms (polyuria, polydipsia, weight loss), immediately measure a random plasma glucose—a single value ≥200 mg/dL (≥11.1 mmol/L) confirms the diagnosis and requires no repeat testing, followed by urgent initiation of insulin therapy without delay. 1, 2

Immediate Diagnostic Steps

Blood Glucose Measurement

• Measure random plasma glucose immediately in any patient presenting with classic symptoms of hyperglycemia 1
• A single random plasma glucose ≥200 mg/dL (≥11.1 mmol/L) with symptoms is diagnostic—do not wait for confirmatory testing 1, 2
• Point-of-care capillary glucose ≥200 mg/dL confirms diabetes when classic symptoms are present, though venous plasma glucose should be obtained for laboratory confirmation (treatment should not be delayed for this) 3
• Critical warning: The metabolic state can deteriorate rapidly in untreated children with type 1 diabetes—delays in diagnosis and treatment must be avoided 1

Assess for Diabetic Ketoacidosis (DKA)

• Check urine for glucose and ketones immediately to assess for DKA 2, 4
• Approximately 50% of new pediatric diabetes cases present with DKA at diagnosis 3
• If marked hyperglycemia (≥250 mg/dL) or ketosis/ketoacidosis is present, initiate insulin therapy immediately 3

Additional Baseline Laboratory Tests

• Measure baseline HbA1c using an NGSP-certified method standardized to the DCCT assay 2, 4
• Obtain fasting plasma glucose if the patient is stable enough (fasting defined as no caloric intake for at least 8 hours) 1

Distinguishing Type 1 from Other Forms of Diabetes

Autoantibody Testing

• Measure pancreatic islet autoantibodies to confirm autoimmune type 1 diabetes: glutamic acid decarboxylase (GAD65), insulinoma-associated protein 2 (IA-2), insulin autoantibodies, and zinc transporter 8 (ZnT8) 2, 4, 3
• The presence of ≥2 autoantibodies confirms autoimmune type 1 diabetes 1

C-Peptide Measurement

• Measure C-peptide levels: low or undetectable C-peptide confirms type 1 diabetes and indicates insulin deficiency 3

Special Populations Requiring Genetic Testing

• All children diagnosed with diabetes in the first 6 months of life require immediate genetic testing for neonatal diabetes, as 80-85% have an underlying monogenic cause 3
• Consider monogenic diabetes (MODY) if there is strong multigenerational family history, negative diabetes autoantibodies, stable mild fasting hyperglycemia, and preserved C-peptide levels 3
• This distinction is critical: GCK-MODY requires no treatment except during pregnancy, while HNF1A-MODY and HNF4A-MODY respond to low-dose sulfonylureas instead of insulin 3

Clinical Features Supporting Type 1 Diabetes

• Acute presentation with rapid symptom onset (typically several days to a few weeks) 1, 3
• Normal weight or recent significant weight loss 3
• Presence of ketones 3
• Obtain detailed family history of diabetes 2

Initial Management

Insulin Therapy Initiation

• Begin intensive insulin therapy immediately with either multiple daily injections (3-4 injections per day of basal and prandial insulin) or continuous subcutaneous insulin infusion (insulin pump) 4, 5
• Initial total daily dose: 0.5 units/kg/day for metabolically stable patients, split 50/50 between basal and prandial insulin 4
• Use rapid-acting insulin analogs (lispro, aspart, glulisine) for prandial doses rather than regular human insulin to reduce hypoglycemia risk 4, 5
• Use long-acting insulin analogs (glargine, detemir) for basal coverage, administered once daily at bedtime for more stable glucose control with less hypoglycemia compared to NPH insulin 4

If DKA is Present

• Treat with intravenous insulin until acidosis resolves, then transition to subcutaneous insulin 4, 3

Urgent Referral

• Refer to pediatric endocrinology within 24-48 hours of diagnosis 3

Screening for Associated Autoimmune Conditions

Celiac Disease Screening

• Screen for celiac disease using tissue transglutaminase (tTG) antibodies with documentation of normal serum IgA levels soon after diagnosis when clinically stable 1, 3
• IgA deficiency is present in 1-3% of patients with celiac disease and will cause falsely low IgA tTG levels, so quantitative serum IgA must be obtained 1

Thyroid Screening

• Screen for thyroid dysfunction soon after diagnosis when clinically stable 3

Common Pitfalls to Avoid

• Never delay insulin therapy while waiting for confirmatory laboratory tests in symptomatic patients 1, 2
• Do not confuse stress hyperglycemia in young children with acute illness for new-onset diabetes—however, these children may have increased risk of eventually developing diabetes 1
• In children under 6 months of age, do not assume type 1 diabetes without genetic testing, as the majority have monogenic diabetes requiring different treatment 3
• Do not use HbA1c alone to rule out diabetes—values below 6.5% do not exclude the diagnosis 2