Initial Laboratory Testing for a Healthy 21-Year-Old Male
For a healthy 21-year-old male with no significant medical history, the essential initial laboratory panel should include: complete blood count (CBC) with differential, comprehensive metabolic panel (CMP), lipid profile, hemoglobin A1c or fasting glucose, TSH, and urinalysis. 1
Core Metabolic and Chemistry Panel
A comprehensive metabolic panel forms the foundation of screening and should include serum electrolytes (sodium, potassium, chloride), serum calcium, magnesium, liver function tests (ALT, AST, bilirubin, alkaline phosphatase, albumin), serum creatinine with estimated glomerular filtration rate (eGFR), blood urea nitrogen, and glucose. 1 This panel provides critical baseline information about renal function, electrolyte balance, hepatic function, and metabolic health that will be essential for future medication dosing decisions and risk stratification. 1
- Renal function assessment is mandatory because baseline creatinine and eGFR are essential for future drug dosing decisions and detecting early kidney disease. 1
- Electrolyte monitoring is critical because abnormalities in potassium, sodium, and calcium can cause serious complications and guide medication management. 1
Hematologic Assessment
A complete blood count with differential is fundamental for detecting anemia, infections, and hematologic abnormalities, serving as a powerful diagnostic tool when combined with history and physical examination. 1 This test provides baseline values for hemoglobin, white blood cell count, and platelet count that are essential for future comparison.
Cardiovascular and Metabolic Risk Screening
A fasting lipid profile including total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides should be obtained to establish baseline cardiovascular risk, even in young adults. 1 The American College of Cardiology recommends lipid profiling as a Class I recommendation for metabolic screening and cardiovascular risk stratification. 1
- For glucose screening, either fasting glucose or hemoglobin A1c is acceptable, though hemoglobin A1c is more convenient as it reflects average glucose control over 2-3 months and does not require fasting. 1
- At age 21, establishing baseline lipid values is important because total cholesterol and HDL cholesterol screening should begin at age 20 according to national guidelines. 2
Endocrine Screening
Thyroid-stimulating hormone (TSH) should be measured routinely to rule out thyroid disorders that can present with diverse symptoms and affect multiple organ systems. 1 Thyroid dysfunction is common and can impact metabolism, cardiovascular function, and overall health.
Urinary Assessment
Urinalysis is essential for detecting proteinuria, microalbuminuria, infections, and other renal abnormalities that may not be apparent from serum creatinine alone. 1
Risk-Based Additional Testing
The following tests should be added based on specific risk factors or clinical indications:
- HIV testing is recommended when risk factors are present, including sexual activity with multiple partners or men who have sex with men. 1
- Hepatitis B testing (HBsAg and HBcAb) should be considered in patients from regions with high prevalence or those with risk factors such as injection drug use or high-risk sexual behavior. 1
- Vitamin B12 and folate levels should be checked if there are concerns about nutritional deficiencies, particularly in patients with restricted diets or symptoms suggesting deficiency. 1
Tests NOT Routinely Indicated
Important clinical pitfalls to avoid:
- Bone scans, brain imaging, and PET scans are not part of routine screening and should only be ordered when specific symptoms or risk factors are present. 1
- Coagulation profiles (PT/INR, PTT) are not routine unless there is bleeding history, planned procedures, or specific clinical indication. 1
- Inflammatory markers (ESR, CRP) should only be obtained when clinically suggested by symptoms or examination findings, not as routine screening. 1
- STD screening beyond HIV should be guided by sexual history and risk factors, not obtained routinely in asymptomatic patients without risk factors. 2