Laboratory Testing Before Initiating GLP-1 Receptor Agonists
Before starting a GLP-1 receptor agonist, you must obtain renal function tests (serum creatinine and eGFR), and should also measure baseline HbA1c, fasting glucose, lipid panel, liver function tests, and amylase/lipase if there is any history of pancreatitis. 1
Essential Laboratory Tests
Renal Function (Mandatory)
- Serum creatinine and estimated glomerular filtration rate (eGFR) are critical because GLP-1 receptor agonists have different dosing requirements and contraindications based on kidney function 1
- Exenatide is contraindicated in end-stage renal disease (ESRD) and not recommended with eGFR < 30 mL/min/1.73 m² 1
- Lixisenatide should be avoided if eGFR < 15 mL/min/1.73 m², with caution and monitoring required for eGFR 15-29 mL/min/1.73 m² 1
- Liraglutide, dulaglutide, and semaglutide require no dose adjustment but should be used with caution in severe renal impairment or ESRD, with monitoring for gastrointestinal reactions 1
Glycemic Parameters
- HbA1c to establish baseline glycemic control and guide treatment expectations 1
- Fasting glucose for baseline metabolic assessment 1
- These values help predict treatment response, as higher baseline HbA1c is associated with increased treatment failure risk (odds ratio 1.3 per one unit increase) 1
Cardiovascular Risk Assessment
- Lipid panel (total cholesterol, LDL, HDL, triglycerides) to assess baseline cardiovascular risk, particularly important since GLP-1 receptor agonists with proven cardiovascular benefit (liraglutide, semaglutide) are preferentially indicated in patients with established atherosclerotic cardiovascular disease 1
Hepatic Function
- Liver function tests (ALT, AST, bilirubin) to establish baseline hepatic status 1
- This is particularly relevant as GLP-1 receptor agonists are metabolized through proteolytic degradation, and some patients may have non-alcoholic fatty liver disease associated with obesity or diabetes 1
Conditional Laboratory Tests
Pancreatic Enzymes (If Indicated)
- Amylase and lipase should be measured if the patient has any history of pancreatitis, as this is a contraindication to GLP-1 receptor agonist therapy 1
- GLP-1 receptor agonists should be discontinued if pancreatitis is suspected and never restarted if confirmed 1
Thyroid Screening (If Risk Factors Present)
- Thyroid function tests are not routinely required but consider if there is personal or family history of thyroid disease, as personal or family history of medullary thyroid cancer or multiple endocrine neoplasia syndrome type 2 (MEN2) are absolute contraindications 1
Important Clinical Caveats
Medication-Specific Considerations
- For exenatide specifically: Renal function is critical as it undergoes proteolytic degradation followed by glomerular filtration with urinary excretion, making it contraindicated in ESRD 1
- For liraglutide and semaglutide: While no dose adjustment is required for renal impairment, monitor eGFR when initiating or escalating doses, especially in patients with adverse gastrointestinal reactions 1
Monitoring During Titration
- Re-check eGFR during dose escalation if the patient develops severe gastrointestinal adverse effects, as these can lead to dehydration and acute kidney injury 1
- Monitor for hypoglycemia risk if the patient is on concurrent insulin or sulfonylureas, as dose reduction of these agents may be required 1
Pre-existing Conditions
- Patients with diabetic retinopathy: Semaglutide has been associated with diabetic retinopathy complications, potentially related to rapid glucose reduction, so baseline retinal assessment may be warranted 1
- Patients with prior gastric surgery or gastroparesis: Shorter-acting GLP-1 receptor agonists may delay gastric emptying and are not recommended in clinically meaningful gastroparesis 1