What is the initial workup for a patient presenting with hyperglycemia?

Initial Workup for Hyperglycemia

The initial laboratory evaluation for patients presenting with hyperglycemia should include complete blood count, urinalysis, serum electrolytes (including calcium and magnesium), blood urea nitrogen, serum creatinine, fasting blood glucose (glycohemoglobin), lipid profile, liver function tests, and thyroid-stimulating hormone. 1

Essential Components of the Workup

History and Physical Examination Focus Points

• Current and past medication use, including insulin, oral hypoglycemics, and other medications
• Alcohol consumption and illicit drug use
• Symptoms of polyuria, polydipsia, polyphagia, weight loss, blurred vision
• Assessment of volume status and orthostatic blood pressure changes
• Measurement of weight and height with BMI calculation
• Mental status evaluation

Laboratory Tests

1. Blood glucose - To confirm hyperglycemia and determine severity
2. Complete blood count - To assess for infection or hemoconcentration
3. Comprehensive metabolic panel:
   • Electrolytes (sodium, potassium, chloride, bicarbonate)
   • Calcium and magnesium
   • Blood urea nitrogen and creatinine (renal function)
   • Liver function tests
4. Urinalysis - To check for glucose, ketones, signs of infection
5. Hemoglobin A1C - To assess chronic glycemic control
6. Lipid profile - For cardiovascular risk assessment
7. Thyroid-stimulating hormone - To rule out thyroid dysfunction

Additional Tests Based on Presentation

• Venous or arterial blood gases - If DKA is suspected (pH, bicarbonate) 1
• Serum osmolality - Particularly if HHS is suspected (glucose >600 mg/dL) 1
• Serum ketones or beta-hydroxybutyrate - If DKA is suspected 1
• Electrocardiogram - Especially in older patients or those with cardiovascular risk factors 1
• Chest radiograph - If respiratory symptoms are present or infection is suspected 1

Diagnostic Algorithm Based on Severity

For Mild Hyperglycemia (Blood glucose <250 mg/dL)

• Complete basic workup as outlined above
• Consider oral glucose tolerance test if diabetes diagnosis is uncertain
• Evaluate for secondary causes (medications, stress, illness)

For Moderate Hyperglycemia (Blood glucose 250-600 mg/dL)

• Complete basic workup plus:
• Check for ketones in urine or blood
• Consider venous pH if symptomatic
• Assess volume status more carefully

For Severe Hyperglycemia (Blood glucose >600 mg/dL)

• Complete basic workup plus:
• Immediate venous or arterial blood gases
• Serum osmolality calculation
• Aggressive assessment of volume status
• Rule out HHS: check mental status, calculate effective serum osmolality using formula: 2[measured Na (mEq/l)] + glucose (mg/dl)/18 1

Important Considerations

Differentiation Between DKA and HHS

• DKA: Blood glucose >250 mg/dL, arterial pH <7.3, bicarbonate <15 mEq/L, moderate ketonuria or ketonemia 1
• HHS: Blood glucose >600 mg/dL, arterial pH >7.3, bicarbonate >15 mEq/L, altered mental status or severe dehydration, minimal ketosis 1

Common Pitfalls to Avoid

1. Relying solely on urine ketones: The nitroprusside method only measures acetoacetic acid and acetone, not beta-hydroxybutyrate (the predominant ketone in DKA). Direct measurement of beta-hydroxybutyrate in blood is preferred 1.

2. Not correcting sodium for hyperglycemia: For each 100 mg/dL glucose >100 mg/dL, add 1.6 mEq to sodium value for corrected serum value 1.

3. Missing underlying infections: Infections can precipitate hyperglycemic crises and may have subtle presentations in hyperglycemic patients 2.

4. Overlooking cardiac complications: Hyperglycemia can be associated with cardiac events, especially in older patients.

By following this systematic approach to the initial workup of hyperglycemia, clinicians can efficiently diagnose the cause, assess severity, and guide appropriate treatment decisions to improve patient outcomes.