GLP-1 medications don’t just change the number on your scale. They affect blood sugar, cholesterol, liver enzymes, kidney function, and more. Tracking these changes through lab work isn’t just good practice—it’s how you prove to yourself (and your insurance company, if applicable) that the medication is working.
Quick Summary
Get a baseline panel before starting treatment, then retest at 3 months, 6 months, and annually thereafter. The core panel includes metabolic markers (A1C, fasting glucose, lipids), organ function (kidney, liver, thyroid), and nutritional status (vitamins, iron).
Baseline Labs (Before Starting)
These labs establish your starting point. Every improvement from here is measurable evidence that treatment is working.
Metabolic Panel
- HbA1C: Your 3-month average blood sugar. Even non-diabetic patients benefit from tracking this—GLP-1s often improve it significantly
- Fasting glucose: A snapshot of current blood sugar regulation
- Fasting insulin: Measures insulin resistance, a root cause of metabolic dysfunction that GLP-1s address directly
- Lipid panel: Total cholesterol, LDL, HDL, and triglycerides. GLP-1 medications typically improve all four
Organ Function
- Comprehensive metabolic panel (CMP): Covers kidney function (BUN, creatinine, eGFR) and liver enzymes (ALT, AST). Essential for establishing baseline organ health
- Thyroid panel (TSH at minimum): GLP-1 medications carry a boxed warning about medullary thyroid carcinoma (based on rodent studies). While the risk in humans appears very low, baseline thyroid function is important
- Lipase/amylase: Baseline pancreatic enzyme levels, relevant because pancreatitis is a rare but serious potential side effect
Nutritional Status
- Vitamin D: Often low in patients with obesity; becomes more important as dietary intake may decrease on GLP-1s
- Vitamin B12: GLP-1 medications can reduce B12 absorption over time due to slowed gastric emptying
- Iron panel (ferritin, TIBC): Reduced food intake can lead to iron deficiency, especially in menstruating women
Optional but Valuable
- hs-CRP (high-sensitivity C-reactive protein): A marker of systemic inflammation that GLP-1s have been shown to reduce
- Uric acid: Can be elevated in metabolic syndrome; GLP-1s may improve it
- Testosterone (men): Obesity suppresses testosterone. Weight loss often restores it, which is worth documenting
- DEXA scan or body composition: Distinguishes between fat loss and muscle loss—critical for optimizing your approach to exercise and protein
Follow-Up Testing Schedule
| Test | Baseline | 3 Months | 6 Months | Annually |
|---|---|---|---|---|
| HbA1C | ✓ | ✓ | ✓ | ✓ |
| Lipid Panel | ✓ | ✓ | ✓ | ✓ |
| CMP (Kidney/Liver) | ✓ | ✓ | ✓ | ✓ |
| TSH (Thyroid) | ✓ | — | ✓ | ✓ |
| Vitamin B12 | ✓ | — | ✓ | ✓ |
| Vitamin D | ✓ | — | ✓ | ✓ |
| Iron/Ferritin | ✓ | — | ✓ | ✓ |
| Lipase/Amylase | ✓ | If symptoms | If symptoms | — |
What to Watch For in Results
Positive Changes (Expected)
Most patients see improvements across the board. The most common positive lab changes include:
- A1C drops 0.5–1.5 points (often normalizing prediabetic levels)
- Triglycerides decrease 15–30%
- LDL cholesterol decreases 5–15%
- Liver enzymes (ALT/AST) normalize as fatty liver improves
- Fasting insulin levels decrease significantly
- hs-CRP (inflammation marker) often drops 20–40%
Yellow Flags (Discuss with Provider)
- Rising creatinine or falling eGFR: Could indicate kidney stress, especially if combined with dehydration from GI side effects
- Dropping B12 levels: Common over time; may require supplementation
- Low iron/ferritin: Especially in women; may need iron supplementation
- Elevated lipase: If accompanied by severe abdominal pain, could indicate pancreatitis (seek immediate care)
Red Flag
If you experience severe abdominal pain that radiates to your back, accompanied by nausea and vomiting, seek emergency care immediately. While rare, pancreatitis requires prompt diagnosis and treatment. Your baseline lipase/amylase values help providers assess whether current levels are abnormally elevated.
Where to Get Lab Work Done
You have several options, and they vary significantly in cost:
- Through your provider: Many telehealth GLP-1 providers include or offer lab work. Some partner with mobile phlebotomy services that come to your home
- Your primary care doctor: Often covered by insurance as part of routine care. Ask your PCP to add the relevant tests to your annual physical
- Direct-to-consumer labs: Services like Quest Direct, Labcorp OnDemand, or Walk-In Lab let you order tests without a doctor’s order, typically at $50–150 for a comprehensive panel
- HSA/FSA eligible: Lab tests are generally eligible expenses for Health Savings Accounts and Flexible Spending Accounts
The Bottom Line
Lab work transforms GLP-1 therapy from “I think it’s working” to “I can see it’s working.” The numbers tell a story that the scale alone can’t: improving metabolic health, reducing cardiovascular risk, and reversing years of inflammation and insulin resistance. Get your baseline before starting, test at 3 and 6 months, then annually. It’s some of the best money you’ll spend on your health.