Before your blood test
Do Ozempic, Wegovy, Mounjaro and Zepbound affect blood test results?
Short answer
Mostly in the ways they are meant to: GLP-1 and GIP/GLP-1 medicines lower fasting glucose and A1c, and as weight falls, triglycerides, LDL, liver enzymes and blood pressure usually improve. Two effects can mislead. Lipase and amylase rise modestly in many people on these drugs without any pancreatitis, so a slightly high lipase on a routine panel is not, by itself, alarming — symptoms decide. And the nausea, vomiting and reduced intake that come with dose increases can leave you dehydrated, which raises creatinine and BUN and lowers eGFR on a draw taken during a rough week. Take your dose on schedule; a fasting draw is unaffected by an injection the day before. If you are on a compounded version, tell the clinician — doses and purity vary.
Medically reviewed by Youmna DiStefano, MD · Last reviewed October 2026
Which results does it affect?
| Marker | Direction | How long | What to do |
|---|---|---|---|
| Glucose (fasting) and A1c | lowers | Glucose within days; A1c over ~3 months | Expected; keep your dose schedule [source] |
| Lipase and amylase | can raise | Mild, persistent elevations are common on treatment | Routine checking is not recommended; test if you have severe abdominal pain, not because of a number [source] |
| Creatinine, BUN (dehydration) | can raise | During nausea, vomiting or poor intake, often after a dose increase | Hydrate; repeat a high creatinine when you are eating and drinking normally [source] |
| Triglycerides, LDL, ALT/AST | lowers | Over weeks to months with weight loss | Expected improvement [source] |
| Heart rate | raises | A few beats per minute while taking | Not a lab value, but noted at the draw [source] |
| Calcitonin | interferes | Not recommended as a routine monitoring test | Thyroid C-cell concern is a label warning for people with a personal or family history of medullary thyroid cancer or MEN2 — discuss with the prescriber rather than screening [source] |
What to expect on your labs — and what is noise
The intended changes are the big ones: fasting glucose and A1c fall, and with the weight loss that follows, triglycerides, LDL, liver enzymes (especially in fatty liver) and blood pressure tend to improve over months. The two findings that generate anxious searches are lipase and creatinine. Many people on GLP-1 medicines run a mildly elevated lipase or amylase with no pancreatitis at all, which is why guidelines do not recommend checking them routinely — pancreatitis is diagnosed on severe, persistent abdominal pain with a markedly high lipase, not on a number alone. Creatinine, meanwhile, rises when you are dry: the weeks around a dose increase, when nausea cuts your fluid intake, are the wrong time for a kidney-function baseline.
Slowed stomach emptying does not change a fasting blood draw — an injection the day before is fine — but it matters for procedures under sedation, where your anesthesia team may ask you to hold a dose.
A note on compounded GLP-1 products
Compounded semaglutide and tirzepatide are not FDA-approved, and the FDA has reported dosing errors and products of uncertain content. If you use one, tell the clinician reading your results exactly what you take and how much; unexpected lab changes are harder to interpret when the dose itself is uncertain. The GLP-1 monitoring panel on TestWell is built for either route: A1c, a metabolic panel for kidney function and electrolytes, lipids and a liver panel — drawn fasting, on your usual schedule.
The tests this affects — order without a doctor's visit
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| GLP-1 Monitoring & Weight ManagementSaves $99.91 vs ordering the tests separately | Panel · 10 tests | $169.99 | Yes | 2–5 business days |
| Hemoglobin A1c | Test | $21.99 | No | 2–4 business days |
| Comprehensive Metabolic Panel | Test · 14 biomarkers | $22.99 | Yes | 1–3 business days |
| Lipid Panel | Test · 4 biomarkers | $24.99 | Yes | 1–3 business days |
| Lipase | Test | $21.99 | No | 1–3 business days |
Common questions
Can I take Ozempic or Mounjaro before a fasting blood test?
Yes. The injection does not affect a fasting draw; keep your usual day and dose. If you are nauseated and not drinking well around a dose increase, wait for a normal week before a kidney-function baseline.
Why is my lipase high on semaglutide?
Mild lipase and amylase elevations are common on GLP-1 medicines without pancreatitis, which is why routine checks are not recommended. Severe, persistent abdominal pain — not the number — is what warrants evaluation.
Which labs should I monitor on a GLP-1 medication?
A1c and fasting glucose for the intended effect, a metabolic panel for kidney function and electrolytes (especially around dose increases), lipids and liver enzymes to track the benefit. The GLP-1 monitoring panel covers these in one fasting draw.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.