Blood tests on GLP-1 medicines like Ozempic and Mounjaro
For people taking semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro, Zepbound) or a similar medicine, for diabetes or for weight.
9 tests explainedAI-verified against cited sources. Awaiting expert reviewLast reviewed 2026-10-19
On a GLP-1 medicine, the tests that matter most depend on why you take it. For diabetes, A1c and glucose show how treatment is going. For everyone, the labels point to kidney function when stomach side effects cause dehydration, and they note that pancreas enzymes can rise. Eating much less can also make some vitamins and minerals harder to get enough of.
The tests that matter most
Most important first. Each one links to its full page, where the note for this group sits near the top.
Hemoglobin A1c (HbA1c)
For people with diabetes, A1c is the usual way to follow treatment. The ADA suggests checking glucose status about every 3 months after a treatment change or when goals aren't met, and at least twice a year once things are steady.
- Usual adult range
- 4.8–5.6 %
Glucose
These medicines lower blood glucose. The labels say that taken with insulin or a sulfonylurea they can raise the chance of low blood sugar, and the Wegovy and Zepbound labels call for monitoring glucose before and during treatment in people with diabetes.
Sources: U.S. Food and Drug Administration (2026), U.S. Food and Drug Administration (2026) and U.S. Food and Drug Administration (2026)
- Usual adult range
- 70–99 mg/dL
Creatinine
The labels describe kidney injury in some people, mostly after nausea, vomiting or diarrhea led to dehydration. They suggest checking kidney function in people who have side effects that could cause fluid loss.
Sources: U.S. Food and Drug Administration (2026), U.S. Food and Drug Administration (2026), U.S. Food and Drug Administration (2026) and U.S. Food and Drug Administration (2026)
- Men, 15+
- 0.74–1.35 mg/dL
- Women, 16+
- 0.59–1.04 mg/dL
eGFR (Creatinine-based)
eGFR is worked out from creatinine and shows how well the kidneys filter. The ADA suggests monitoring kidney function when these medicines are started or the dose goes up in people with reduced kidney function who report severe stomach side effects.
- Usual adult range
- 60 and above mL/min/1.73 m²
Lipase
Lipase, a pancreas enzyme, can rise on these medicines. The Wegovy, Mounjaro and Zepbound labels say the meaning of a rise without other signs of pancreatitis is unknown, and none of the four labels calls for routine lipase tests. Instead they ask clinicians to watch for symptoms, such as severe or lasting belly pain that sometimes spreads to the back.
Sources: U.S. Food and Drug Administration (2026), U.S. Food and Drug Administration (2026), U.S. Food and Drug Administration (2026) and U.S. Food and Drug Administration (2026)
- Men, 18+
- 13–78 U/L
- Women, 18–70
- 14–72 U/L
Triglycerides
In the main weight-loss trials of liraglutide and tirzepatide, triglycerides and cholesterol improved along with weight, a 2025 joint advisory reports.
- Usual adult range
- up to 149 mg/dL
Vitamin B12 (Cobalamin)
Eating much less can make it harder to get enough B12, which a 2025 joint advisory lists among nutrients of concern on these medicines. Many people with diabetes also take metformin, which the ADA links to low B12.
Sources: The American Journal of Clinical Nutrition (2025) and American Diabetes Association (2026)
- Usual adult range
- 232–1,245 pg/mL
Ferritin
Iron is one of the nutrients of concern a 2025 joint advisory names for people eating much less on these medicines. It suggests extra lab tests before starting for people with certain histories, such as weight-loss surgery or a past deficiency.
- Men, 20–59
- 30–400 ng/mL
- Men, 60+
- 31–409 ng/mL
Vitamin D (25-Hydroxy)
Vitamin D is also on the 2025 joint advisory's list of nutrients that can run short when calorie intake drops sharply on these medicines.
- Usual adult range
- 30–100 ng/mL
Ranges shown are the usual adult ranges labs print. The range on your own report is the one your result is judged against.
Getting results you can compare
- If you've had vomiting or diarrhea, or trouble keeping fluids down, mention it before a kidney test. The labels link most kidney problems on these medicines to dehydration from stomach side effects.
Sources: U.S. Food and Drug Administration (2026) and U.S. Food and Drug Administration (2026)
- A 2025 joint advisory says extra lab tests may be useful before starting for people with a recent or past very low-calorie diet, weight-loss surgery, celiac disease, another inflammatory condition that can cause nutrient shortfalls, or a past nutrient deficiency.
Good to know
- The labels list pancreatitis, gallbladder problems and kidney injury from dehydration among their warnings. The Wegovy label notes that large or rapid weight loss can raise the chance of gallstones.
Sources: U.S. Food and Drug Administration (2026) and U.S. Food and Drug Administration (2026)
- Eating much less can leave gaps in vitamins and minerals. The advisory names iron, calcium, magnesium, zinc and vitamins A, D, E, K, B1, B12 and C as examples of nutrients of concern, especially at very low calorie intakes. It suggests re-checking diet and nutrient status during treatment, but gives no set schedule or list of blood tests.
- People sometimes ask about a calcitonin blood test because of the thyroid warning on these labels. The labels say routine calcitonin monitoring is of uncertain value.
Sources: U.S. Food and Drug Administration (2026) and U.S. Food and Drug Administration (2026)
Questions you could ask
- Which blood tests would be useful before and during this medicine?
- How often should we recheck my A1c and kidney function?
- If I have stomach side effects, when should my kidney function be checked?
- Is it worth checking any vitamins or iron while I'm eating much less?
- How should we read a raised lipase if I have no symptoms?
Sources
- OZEMPIC (semaglutide) injection: prescribing information (revised 5/2026), U.S. Food and Drug Administration (2026)
- WEGOVY (semaglutide) injection and tablet: prescribing information (revised 6/2026), U.S. Food and Drug Administration (2026)
- MOUNJARO (tirzepatide) injection: prescribing information (revised 8/2026), U.S. Food and Drug Administration (2026)
- ZEPBOUND (tirzepatide) injection: prescribing information (revised 8/2026), U.S. Food and Drug Administration (2026)
- 9. Pharmacologic Approaches to Glycemic Treatment: Standards of Care in Diabetes-2026, American Diabetes Association (2026)
- 6. Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises: Standards of Care in Diabetes-2026, American Diabetes Association (2026)
- Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society, The American Journal of Clinical Nutrition (2025)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-19. How we build and check these pages.
Educational information, not medical advice. Blood Test Tracker doesn’t diagnose or treat, and it doesn’t replace your clinician. Talk with your clinician before changing medications, supplements or care.