Baseline Testing Before Initiating GLP-1 Analogues
The 2025 American Diabetes Association guidelines do not mandate specific baseline laboratory testing before starting GLP-1 receptor agonists, though comprehensive metabolic assessment is prudent for optimizing overall diabetes management and identifying comorbidities that influence treatment selection. 1
Essential Baseline Assessments
Glycemic Parameters
- HbA1c measurement to establish baseline glycemic control and set individualized treatment goals 1
- Fasting plasma glucose if HbA1c is unavailable or unreliable (hemoglobinopathies, recent blood loss)
Renal Function Assessment
- Estimated glomerular filtration rate (eGFR) to identify chronic kidney disease and guide overall diabetes management strategy 2
- Urinary albumin-creatinine ratio to detect albuminuria, which influences cardiovascular risk stratification and may favor GLP-1 RA selection for renal protection 2
Cardiovascular Evaluation
- Documentation of cardiovascular disease status (established atherosclerotic CVD, heart failure, or multiple risk factors) to identify patients who would benefit most from GLP-1 RAs with proven cardiovascular benefits 1, 2
- Left ventricular ejection fraction documentation when heart failure symptoms are present, as this influences overall treatment algorithm 2
Gastrointestinal History
- Screen for personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 (absolute contraindications to GLP-1 RA therapy) 3
- History of pancreatitis (relative contraindication requiring careful risk-benefit assessment) 3
- Current gastrointestinal symptoms including nausea, vomiting, or gastroparesis, as GLP-1 RAs delay gastric emptying 1, 4
Medication Review and Adjustment Planning
Hypoglycemia Risk Assessment
- Review concurrent sulfonylurea or insulin therapy - these require dose reduction before GLP-1 RA initiation to prevent hypoglycemia 3
- Without concurrent insulin or sulfonylureas, GLP-1 RAs carry minimal hypoglycemia risk 3
Nutritional Considerations
- Baseline vitamin D, iron studies, and B12 levels may be considered, particularly in patients at risk for malnutrition, as GLP-1 RA therapy is associated with micronutrient deficiencies including vitamin D deficiency (7.5% at 6 months, 13.6% at 12 months) and 26-30% lower ferritin levels 5
- More than 60% of GLP-1 RA users consume below estimated requirements for calcium and iron 5
Clinical Caveats
No routine imaging or specialized testing is required before GLP-1 RA initiation. The focus should be on identifying contraindications, assessing cardiovascular and renal comorbidities that influence agent selection, and planning for medication adjustments to prevent hypoglycemia 1, 3.
The most common barrier to GLP-1 RA use is clinical inertia rather than lack of appropriate baseline testing. Treatment should not be delayed for extensive workup when basic assessments confirm appropriateness 6.
For patients with established atherosclerotic cardiovascular disease, prioritize GLP-1 RAs with proven cardiovascular benefit (liraglutide, injectable semaglutide, dulaglutide, albiglutide) regardless of baseline HbA1c or background therapy 3, 7.