Laboratory Workup for Obesity
The initial laboratory evaluation for patients with obesity should include a comprehensive metabolic panel, fasting lipid profile, thyroid function tests, and screening for abnormal blood glucose. 1
Core Laboratory Tests
Essential Baseline Tests
- Comprehensive metabolic panel (including electrolytes, liver enzymes, and renal function) 1
- Fasting lipid profile (total cholesterol, HDL, LDL, triglycerides) 1
- Thyroid function tests 1, 2
- Fasting glucose and/or hemoglobin A1C 1
Additional First-Line Tests
- Complete blood count 3
- Liver function tests (to assess for metabolic-associated fatty liver disease) 1
- Waist circumference measurement (not a lab test but essential complementary assessment) 1, 3
Targeted Testing Based on Clinical Findings
If history and physical examination suggest specific underlying causes of obesity, consider these additional tests:
Endocrine Disorders
- Cushing syndrome screening (if clinically suspected) 1, 2
- Sex hormone levels (for suspected PCOS or hypogonadism) 1, 2
- Growth hormone levels (if growth hormone deficiency suspected) 2
Metabolic Syndrome Assessment
- Three or more of the following indicate metabolic syndrome 1:
- Elevated waist circumference (≥88 cm for women, ≥102 cm for men)
- Triglycerides ≥150 mg/dL
- Fasting plasma glucose ≥100 mg/dL
- Blood pressure ≥130/85 mm Hg
- HDL-C <40 mg/dL in men, <50 mg/dL in women
Sleep Disorders
- Consider polysomnography if obstructive sleep apnea is suspected (especially with large neck circumference) 1
Monitoring Recommendations
- Repeat laboratory testing should be performed periodically to monitor for obesity-related complications
- Lipid profile and glucose monitoring should be performed at 3 months and then annually 1
- More frequent monitoring may be needed for patients on weight loss medications or with existing comorbidities
Special Considerations
Genetic Testing
- Consider genetic testing for monogenic or syndromic obesity if there are alarm symptoms such as early-onset obesity, dysmorphic features, hyperphagia, or striking family history 2
Cardiovascular Risk Assessment
- ECG may be indicated for patients with cardiovascular risk factors 1, 4
- Consider more comprehensive cardiovascular evaluation for patients with additional cardiac risk factors 4
Pitfalls and Caveats
- BMI alone is an insufficient measure of health risk at the individual level and should be complemented with other anthropometric measurements 5
- Secondary causes of obesity (medication effects, endocrine disorders) can be missed without appropriate screening 2
- Laboratory values may be normal despite significant obesity-related health risks
- Focusing solely on laboratory abnormalities without addressing behavioral and environmental factors will lead to suboptimal outcomes
By following this systematic laboratory approach to obesity evaluation, clinicians can identify underlying causes, assess for complications, and develop targeted treatment strategies that address the specific needs of each patient with obesity.