What labs should be ordered before initiating Zepbound (tirzepatide) therapy?

Laboratory Tests Required Before Initiating Zepbound (Tirzepatide) Therapy

Before initiating Zepbound (tirzepatide) therapy, a comprehensive metabolic panel including liver function tests, renal function assessment, and fasting blood glucose or HbA1c should be ordered.

Essential Baseline Laboratory Tests

• Complete blood count (CBC) to establish baseline hematological parameters 1
• Comprehensive metabolic panel including:
  • Liver function tests (ALT, AST, alkaline phosphatase, bilirubin) to screen for pre-existing liver disease 1, 2
  • Renal function tests (BUN, creatinine, eGFR) to evaluate kidney function 1, 2
  • Electrolytes (sodium, potassium, calcium, magnesium) 2
• Fasting blood glucose and/or HbA1c to establish baseline glycemic status 3, 4
• Lipid panel (total cholesterol, LDL, HDL, triglycerides) to assess cardiovascular risk 3, 4
• Pregnancy test for women of childbearing potential due to potential risks during pregnancy 1, 2

Rationale for Laboratory Testing

• Tirzepatide is a dual GIP/GLP-1 receptor co-agonist that significantly reduces HbA1c (1.24-2.58%) and body weight (5.4-11.7 kg) 3
• Baseline laboratory tests are essential to:
  • Identify potential contraindications before initiating therapy 1
  • Establish reference values for subsequent monitoring 1
  • Assess pre-existing conditions that may be affected by treatment 2

Monitoring Recommendations After Initiation

• Liver function tests should be checked approximately 1 month after initiating therapy and then every 3-6 months during continued treatment 1
• Renal function tests should be monitored periodically, especially in patients with pre-existing renal impairment 2
• Blood glucose and/or HbA1c should be monitored regularly to assess treatment efficacy 4
• Blood pressure should be monitored due to potential cardiovascular effects 2, 4

Clinical Considerations and Precautions

• Failure to obtain baseline laboratory tests may lead to difficulty interpreting subsequent abnormalities 1
• Tirzepatide has been associated with gastrointestinal side effects (nausea, vomiting, diarrhea, constipation) that are more common at higher doses 3
• The medication has shown favorable effects on multiple cardiometabolic parameters including blood pressure, visceral adiposity, and circulating triglycerides 4
• Cardiovascular events should be monitored, though clinical trials have shown a trend toward reduction in MACE-4 events (non-fatal myocardial infarction, non-fatal stroke, cardiovascular death, and hospital admission for angina) 3

Special Populations

• In patients with pre-existing liver disease, more frequent monitoring of liver function may be warranted 2
• For patients with renal impairment, dose adjustments and more careful monitoring may be necessary 2
• Women of childbearing potential should be counseled about the importance of effective contraception during treatment 1