Laboratory Testing Before Initiating GLP-1 Receptor Agonist Therapy
Before starting GLP-1 receptor agonist therapy, a comprehensive metabolic panel (CMP), estimated glomerular filtration rate (eGFR), and urine albumin-to-creatinine ratio (UACR) should be obtained to assess baseline kidney function and identify potential contraindications.
Essential Laboratory Tests
Baseline Kidney Function Assessment
- eGFR measurement - Critical for dosing considerations and to identify contraindications 1
- Urine albumin-to-creatinine ratio (UACR) - To assess for albuminuria and kidney disease 1
- Comprehensive metabolic panel (CMP) - Including:
- Glucose
- Electrolytes (sodium, potassium, chloride, carbon dioxide)
- BUN and creatinine
- Calcium
- Liver function tests (ALP, ALT, AST, bilirubin)
- Albumin and total protein 1
Glycemic Parameters
- Hemoglobin A1C (HbA1c) - To establish baseline glycemic control 1
- Fasting plasma glucose - For baseline assessment 1
Additional Recommended Tests
Cardiovascular Risk Assessment
- Lipid panel - To assess baseline cardiovascular risk 1
- High-sensitivity C-reactive protein (hsCRP) - Consider if elevated cardiovascular risk 1
Other Relevant Tests
- Thyroid function tests - Particularly important given theoretical concerns about medullary thyroid cancer risk 2, 3
- Pancreatic enzymes (amylase, lipase) - Consider in patients with history of pancreatitis 1, 2
Clinical Considerations for Specific Patient Populations
Patients with Renal Impairment
- While most GLP-1 RAs can be used in patients with reduced renal function, dose adjustment may be necessary for some agents 1
- Some GLP-1 RAs should be used with caution in patients with severe renal impairment (eGFR <30 ml/min/1.73 m²) 1, 2
Patients with Retinopathy
- Baseline eye examination - Recommended if not performed within the past 12 months, particularly important for patients with pre-existing diabetic retinopathy 1, 2
Patients with Cardiovascular Disease
- Baseline cardiovascular assessment - Including blood pressure measurement and assessment of cardiovascular risk factors 1
Monitoring After Initiation
- Blood glucose monitoring - More frequent monitoring recommended during the first 4 weeks of therapy 2
- Renal function - Periodic monitoring of eGFR and UACR, especially in patients with pre-existing kidney disease 1
- Electrolytes - Particularly important when combining GLP-1 RAs with other medications that may affect electrolyte balance 1
Important Precautions
- Avoid concomitant DPP-4 inhibitor use - These medications should be discontinued before starting GLP-1 RA therapy 2
- Adjust insulin or sulfonylurea doses - Typically reduce insulin by approximately 20% and sulfonylureas by 50% when initiating GLP-1 RA therapy to prevent hypoglycemia 2, 4
- Screen for contraindications - Including personal or family history of medullary thyroid carcinoma, Multiple Endocrine Neoplasia syndrome type 2, or history of pancreatitis 2
By ensuring appropriate laboratory testing before initiating GLP-1 receptor agonist therapy, clinicians can optimize treatment safety and efficacy while minimizing potential adverse effects.