What are the routine laboratory tests to order for a general medical evaluation?

Routine Laboratory Tests for General Medical Evaluation

For a general medical evaluation, order a complete blood count (CBC), comprehensive metabolic panel (CMP) including electrolytes, renal function (BUN/creatinine), liver function tests, fasting glucose, lipid profile, thyroid-stimulating hormone (TSH), and urinalysis as your baseline routine laboratory workup. 1

Core Laboratory Panel

Hematologic Assessment

• Complete Blood Count (CBC) with differential to evaluate for anemia, infection, hematologic malignancies, and immune function 1
• This single test provides critical information about red blood cells, white blood cells, platelets, and can predict cardiovascular disease and metabolic disorders 2

Metabolic and Renal Function

• Comprehensive metabolic panel including:
  • Serum electrolytes (sodium, potassium, chloride, bicarbonate) 1
  • Blood urea nitrogen (BUN) and serum creatinine to assess kidney function 1
  • Fasting blood glucose (or glycohemoglobin/HbA1c for diabetes screening) 1
  • Serum calcium and magnesium 1

Hepatic Function

• Liver function tests including ALT, AST, alkaline phosphatase, bilirubin, and albumin 1
• These assess hepatic synthetic function and detect liver disease 1

Endocrine Screening

• Thyroid-stimulating hormone (TSH) to screen for thyroid dysfunction, which commonly presents with non-specific symptoms 1
• Thyroid disease can masquerade as psychiatric or behavioral problems and should not be missed 1

Cardiovascular Risk Assessment

• Lipid profile (total cholesterol, LDL, HDL, triglycerides) for cardiovascular risk stratification 1
• This is essential for primary prevention strategies 1

Urinalysis

• Urinalysis to screen for renal disease, diabetes, urinary tract infections, and other metabolic abnormalities 1

Additional Context-Specific Tests

When Anemia or Nutritional Deficiency is Suspected

• Iron studies (serum iron, ferritin, total iron-binding capacity) 1
• Vitamin B12 level, particularly in patients with neurologic symptoms or macrocytic anemia 1

When Inflammation is Suspected

• C-reactive protein (CRP) as a marker of systemic inflammation 1
• Note that CRP may be normal in some inflammatory conditions, so clinical context matters 1

Critical Pitfalls to Avoid

Do not order "routine" urine drug screens without clinical indication - studies show only 5% positivity with no management changes when ordered routinely 1. Order toxicology only when history or examination suggests intoxication or withdrawal 1.

Interpret sodium in context of glucose - hyperglycemia causes falsely low sodium readings; correct by adding 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL 3. This prevents misdiagnosis of hyponatremia 3.

Do not dismiss trace urine ketones in symptomatic patients - any ketones can represent early metabolic crisis, particularly in diabetic patients 4. If present with symptoms, immediately check serum glucose, β-hydroxybutyrate, and arterial blood gas 4.

Algorithmic Approach to Ordering

1. Start with the core panel (CBC, CMP, TSH, lipids, urinalysis) for all general evaluations 1
2. Add iron studies and B12 if anemia is present on CBC or patient has fatigue/neurologic symptoms 1
3. Add inflammatory markers (CRP) if chronic inflammatory condition is suspected 1
4. Obtain baseline values for future comparison, as longitudinal trends are often more informative than single values 1

This standardized approach ensures comprehensive screening while avoiding unnecessary testing that adds cost without clinical benefit 1.