What blood work is recommended before starting Wegovy (semaglutide) for weight loss in a patient with a history of diabetes or prediabetes and potential renal impairment?

Blood Work Required Before Starting Wegovy for Weight Loss

Before initiating Wegovy (semaglutide), you must obtain baseline renal function (serum creatinine and eGFR), lipid panel, hemoglobin A1c (if diabetes/prediabetes present), and screen for personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. 1

Mandatory Baseline Laboratory Tests

Renal Function Assessment

• Serum creatinine and estimated glomerular filtration rate (eGFR) are required before starting Wegovy, particularly given the patient's potential renal impairment 1. The American Heart Association specifically recommends assessing renal function before initiating GLP-1 receptor agonists 1.
• While no dose adjustment is needed for renal impairment (semaglutide pharmacokinetics are not significantly affected even in end-stage renal disease) 2, 3, baseline assessment is critical for monitoring purposes 1.
• Urinary albumin-to-creatinine ratio should be obtained if diabetes or prediabetes is present, as this is part of comprehensive diabetes evaluation 4.

Metabolic Panel

• Lipid profile (total cholesterol, LDL, HDL, triglycerides) is recommended for patients with dyslipidemia or cardiovascular risk factors 1.
• Hemoglobin A1c is required if the patient has diabetes or prediabetes 1. This serves as baseline for monitoring glycemic control 4.
• Serum potassium should be checked if the patient is on ACE inhibitors, ARBs, or diuretics 4.

Hepatic Function

• Liver function tests are recommended as part of baseline assessment, though hepatic impairment does not affect semaglutide pharmacokinetics 2, 1.

Critical Screening Requirements

Thyroid Cancer Risk Assessment

• You must screen for personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) before prescribing Wegovy 1. This is an absolute contraindication 4, 1.
• Semaglutide caused thyroid C-cell tumors in rodent studies, though human relevance is unknown 2.

Pregnancy and Contraception

• Pregnancy testing is required in women of childbearing potential, as pregnancy is a contraindication 1.
• Reliable contraception must be documented during treatment 1.
• Wegovy should be discontinued at least 2 months before planned pregnancy due to the long washout period (approximately 5 weeks after last dose) 2.

Pancreatitis History

• Document any history of pancreatitis, as this is a contraindication to GLP-1 receptor agonist therapy 4, 1.

Additional Baseline Assessments

Ophthalmologic Evaluation

• Patients should undergo guideline-recommended eye examinations if not done within the last 12 months 4. Semaglutide was associated with increased diabetic retinopathy complications in SUSTAIN-6, particularly with rapid glucose reduction 4.

Blood Pressure and Heart Rate

• Baseline blood pressure and heart rate should be documented 4. GLP-1 receptor agonists can modestly lower blood pressure but may increase heart rate 4.

Monitoring Schedule After Initiation

Early Follow-up (First 4 Weeks)

• Recheck serum creatinine, eGFR, and potassium within 1-2 weeks if the patient has pre-existing renal impairment 4.
• Monitor for dehydration symptoms (lightheadedness, orthostasis, weakness), as GI side effects can lead to volume depletion and acute kidney injury 4, 1.

Ongoing Monitoring

• Renal function and electrolytes should be monitored at least annually, or more frequently if chronic kidney disease is present 4.
• Hemoglobin A1c should be rechecked every 3 months if the patient has diabetes 4.
• Lipid panel annually unless on lipid-lowering therapy requiring more frequent monitoring 4.

Common Pitfalls to Avoid

• Do not skip renal function testing even though dose adjustment is not required—baseline values are essential for detecting acute kidney injury from dehydration 1, 5.
• Do not forget thyroid cancer screening—this is a boxed warning contraindication 2.
• Do not initiate in patients with active gallbladder disease, as GLP-1 receptor agonists increase risk of cholecystitis 4.
• Reduce insulin or sulfonylurea doses by 20-30% at initiation if the patient is on these medications to prevent hypoglycemia 4.