Lab Work for GLP-1 Treatment: What to Expect

You have researched GLP-1 medications and understand how they work. You may be wondering what comes before the prescription: the lab work. Will a provider order blood tests before writing a prescription? What do those tests show? And who pays for them?

This page walks through what the FDA labels say about labs, the tests a prescriber may order before and during treatment and why, and the questions to ask any program about how it handles lab work.

Why Lab Work Is Required Before Starting GLP-1

GLP-1 medications are prescription medications that need medical supervision. They are not over-the-counter supplements. Here is the part many people do not expect: the FDA labels for Wegovy and Zepbound do not list a required baseline lab panel for weight management.^[1][2] Whether you need blood work first is up to the licensed provider who evaluates you, and practices vary. Many prescribers order labs anyway, to answer two questions:

Is this medication medically appropriate for you? Both labels carry a boxed warning about thyroid C-cell tumors seen in rodents, and both medications are contraindicated if you have a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).^[1][2] That screening comes from your health history, not a blood test. The Wegovy label says routine monitoring of serum calcitonin or thyroid ultrasound is of uncertain value for early detection of MTC.^[1] Labs help with other questions, such as how well your kidneys work and whether you have undiagnosed diabetes.

What is your baseline health status? A baseline gives the provider something to compare to later. The labels list several monitoring considerations that connect to lab results or health history:^[1][2]

• Kidney function: acute kidney injury has been reported, mostly in people who became dehydrated from nausea, vomiting, or diarrhea. The labels say to monitor kidney function in people reporting those side effects, especially when starting and increasing the dose.
• Blood sugar: in people with diabetes, the labels say to monitor blood glucose before starting and during treatment. The risk of low blood sugar goes up when these medications are taken with insulin or a sulfonylurea, and the dose of those medications may need to be lowered.
• Diabetic retinopathy: people with type 2 diabetes and a history of diabetic retinopathy should be monitored for progression.
• Gallbladder and pancreas: gallbladder disease and acute pancreatitis have been reported. These are watched for through symptoms (for example, severe or persistent abdominal pain) rather than routine baseline tests.

Pre-Treatment Labs (Baseline Panel)

If a provider orders baseline labs, these are tests you may see. Not every provider orders all of them, and some order none.

Additional Lab Sometimes Ordered

Some providers also check ferritin (iron storage levels). Hair loss is listed among the common side effects in both the Wegovy and Zepbound labels,^[1][2] and some providers check iron levels when hair loss is a concern. If a provider orders it, ask what they will do with the result.

Why HbA1c Is Particularly Important

Your HbA1c result helps a provider understand your blood sugar. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), these are the standard ranges:^[3]

HbA1c below 5.7% = Normal range. This does not change whether a GLP-1 medication can be considered for weight management; it means blood sugar is not part of the clinical picture in the same way.

HbA1c 5.7% to 6.4% = Prediabetes range. A provider may include blood sugar in your treatment goals alongside weight and may recheck HbA1c during treatment.

HbA1c 6.5% or higher = Diabetes range. A provider confirms a diagnosis. Diabetes does not by itself rule out GLP-1 treatment. Some GLP-1 medications, such as Mounjaro, are FDA-approved to improve blood sugar control in type 2 diabetes,^[4] and the Wegovy and Zepbound labels call for blood glucose monitoring before and during treatment in people with diabetes.^[1][2] If you take insulin or a sulfonylurea, tell the provider, because the labels say these raise the risk of low blood sugar.

The key point: your HbA1c alone does not decide whether a GLP-1 medication is appropriate. It is one input to the licensed provider’s assessment.

Ongoing Monitoring Labs

The labels do not set a fixed lab schedule for weight management. Monitoring is tied to your health history and to symptoms. Here is how it often lines up:^[1][2]

The frequency and specific tests a provider orders vary with your health history. For example, the Wegovy label notes that kidney-related side effects were more common in trial participants with a history of kidney impairment and during dose titration,^[1] so a provider may check kidney function more often if your baseline was low.

How the Process Should Work

Lab work can be a hidden cost. Some programs advertise a monthly fee and then bill separately for lab draws, visits, or shipping. Others include certain labs. Neither approach is wrong, but you should know which one you are signing up for. Compare the total cost: medication, dose increases, provider visits, labs, shipping, membership fees, and cancellation terms.

Questions to ask any program before you pay:

• Which labs are required, and why? Ask whether labs are needed before the first prescription, at follow-up, or both.
• Who orders them? Ask whether the program’s prescriber sends the lab order, or whether you are expected to get labs through your own primary care provider.
• Where are they drawn? Ask whether there is a lab location near you, whether at-home kits are accepted, and whether recent results from your own provider can be used.
• What do they cost? Ask whether labs are included in the fee, billed by the lab, or billed to your insurance, and what you pay if insurance does not cover them.
• How are results shared? Ask how long results usually take, who reviews them, and how the provider will contact you about anything abnormal.

What Happens If Lab Results Show Something Abnormal

Lab results sometimes flag abnormalities. This does not automatically mean a GLP-1 medication is off the table. A licensed provider looks at the result together with your health history. Some examples:

If your kidney function is reduced: Neither the Wegovy nor the Zepbound label lists kidney impairment as a contraindication, and the Zepbound label recommends no dosage adjustment for kidney impairment.^[1][2] The labels do warn about acute kidney injury with dehydration, and the Wegovy label notes kidney-related side effects were more common in participants with a history of kidney impairment.^[1] A provider may monitor more closely, coordinate with a kidney specialist, or decide the medication is not appropriate.

If your liver enzymes are elevated: Elevated liver enzymes have many causes, including fatty liver disease, which is common in people with metabolic conditions. The Zepbound label recommends no dosage adjustment for hepatic impairment,^[2] and Wegovy is also FDA-approved, under accelerated approval, to treat noncirrhotic MASH (metabolic dysfunction-associated steatohepatitis) with moderate to advanced liver fibrosis in adults.^[1] The provider will look for the cause and discuss what it means for you.

If your HbA1c is very high or your fasting glucose is severely elevated: This points to poorly controlled diabetes. The provider may still consider a GLP-1 medication, may want closer glucose monitoring, and may refer you to your primary care provider or an endocrinologist, especially if you take insulin or a sulfonylurea.^[1][2]

If your TSH is abnormal: An abnormal TSH does not by itself rule out GLP-1 treatment. The provider will likely recommend that you see your primary care provider about thyroid management. Tell every provider you see about all the medications you take.

If your ferritin is low (iron deficiency): The provider may look into the cause and discuss whether treatment, such as iron supplementation, is appropriate.

The licensed provider makes the final clinical determination. They should explain any significant findings and discuss whether treatment is medically appropriate for you.

At-Home Labs vs. In-Person Draws

You may have seen ads for at-home blood collection kits. Some programs accept them; others require a draw at a lab location. Rules on which tests can be done at home, and how, depend on the test and the lab. Questions to ask:

Which collection methods does the program accept? Ask whether an at-home kit covers every test the provider wants, or only some of them.

Is the lab certified? The Centers for Medicare & Medicaid Services (CMS) regulates laboratory testing performed on people in the US through the Clinical Laboratory Improvement Amendments (CLIA) program.^[5] Ask the program which lab processes the sample and whether it holds CLIA certification.

Is there a lab near you? If the program requires an in-person draw, use the lab’s own location finder to check before you sign up. If you live in a rural area, ask what the program does when no location is nearby.

Summary

GLP-1 treatment is a medical treatment, not a supplement. The FDA labels for Wegovy and Zepbound do not require a specific baseline lab panel for weight management, but they do list monitoring considerations, including kidney function with dehydration, blood sugar in people with diabetes, and diabetic retinopathy history. Many prescribers order baseline labs, and practices vary. Before you choose a program, ask which labs it requires, who orders them, where they are drawn, and what they cost.

A licensed provider decides whether a prescription is appropriate for you.

Important disclosures

This content is for general education and is not medical advice. Talk with a licensed provider about your situation.

Compounded medications are not FDA-approved. The FDA does not review them for safety, effectiveness, or quality. Compounded semaglutide and tirzepatide are not the same as brand-name products such as Wegovy, Zepbound, or Mounjaro, and they may differ in formulation, purity, and potency.

Wegovy is a trademark of Novo Nordisk A/S. Zepbound and Mounjaro are trademarks of Eli Lilly and Company. Transformation Health is not affiliated with or endorsed by these companies.

Citations

[1] Novo Nordisk. WEGOVY (semaglutide) injection and tablets, prescribing information. Revised 06/2026. Boxed warning, Contraindications (4), Warnings and Precautions (5.1-5.8), Adverse Reactions (6). https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/215256s025lbl.pdf

[2] Eli Lilly and Company. ZEPBOUND (tirzepatide) injection, prescribing information. Revised 08/2026. Boxed warning, Contraindications (4), Warnings and Precautions (5.3-5.8), Renal and Hepatic Impairment (8.6, 8.7). https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/217806Orig1s041correctedlbl.pdf

[3] National Institute of Diabetes and Digestive and Kidney Diseases. “The A1C Test & Diabetes.” Last reviewed April 2018. https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test (Accessed 2026-10-16.)

[4] Eli Lilly and Company. MOUNJARO (tirzepatide) injection, prescribing information. Revised 04/2026. Indications and Usage (1). https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/215866Orig1s052lbl.pdf

[5] Centers for Medicare & Medicaid Services. “Clinical Laboratory Improvement Amendments (CLIA).” Page last modified 10/07/2026. https://www.cms.gov/medicare/quality/clinical-laboratory-improvement-amendments (Accessed 2026-10-16.)