Blood Tests for Assessing Obesity
Basic laboratory evaluation for obesity should include a comprehensive metabolic panel, fasting lipid profile, and thyroid function tests as the essential initial workup. 1, 2
Core Initial Laboratory Tests
All adults with obesity require the following baseline blood work to investigate potential endocrine causes and examine metabolic syndrome components 1:
- Comprehensive metabolic panel - assesses kidney function (creatinine, BUN), liver enzymes (ALT, AST, alkaline phosphatase), and electrolytes 1, 2
- Fasting lipid profile - includes total cholesterol, LDL, HDL, and triglycerides to evaluate dyslipidemia 1, 2
- Thyroid function tests - TSH at minimum (with free T4 and free T3 if indicated) to rule out hypothyroidism as a secondary cause 1, 2
- Fasting blood glucose or hemoglobin A1c - screens for diabetes or prediabetes, particularly recommended for adults aged 40-70 years with overweight or obesity 1, 2
Additional Tests Based on Clinical Suspicion
Secondary tests should be ordered when history or physical examination suggests specific obesity-related complications 1:
- Overnight dexamethasone suppression test or 24-hour urinary free cortisol - if Cushing's syndrome is suspected (central obesity, moon facies, violaceous striae, thin atrophic skin) 1, 2
- Liver function tests - to evaluate for metabolic-associated fatty liver disease (NAFLD/NASH), which is common in obesity 1, 2
- Additional glucose monitoring - fasting glucose may be assessed at younger ages if family history of type 2 diabetes or presence of acanthosis nigricans 1
Pediatric Considerations
For children and adolescents with obesity, similar tests are appropriate including liver function, lipid profile, fasting glucose, hemoglobin A1c, and uric acid 1. The decision to assess these parameters should be based on the child's personal and family history, with fasting glucose particularly important if there is family history of type 2 diabetes or evidence of acanthosis nigricans 1.
Common Pitfalls to Avoid
The most significant clinical error is failing to screen comprehensively even after obesity diagnosis - research shows only 22% of diagnosed obese pediatric patients were screened for all three major obesity-related conditions (diabetes, liver abnormalities, and lipid abnormalities) 3. Do not rely solely on BMI for assessment - waist circumference should be measured in all patients with BMI <35 kg/m² to capture central adiposity that BMI may miss 1. Screening rates plateau or decline over time despite ongoing obesity, so maintain vigilance with regular monitoring 3.