Lab Tests to Monitor While Taking Wegovy (Semaglutide)

GLP-1 receptor agonists like Wegovy (semaglutide) have become one of the most talked-about treatments in medicine. Millions of people are now using them for weight loss and metabolic health — but most are never told which lab tests they should be getting before they start, or how to monitor their health while they are on the medication.

This guide covers the exact blood tests that matter, why each one is ordered, and when to check them.

Semaglutide works by mimicking a gut hormone that regulates appetite and blood sugar. It is highly effective — but it also affects your kidneys, liver, thyroid, and nutritional status in ways that are worth tracking. Baseline labs give you a starting point. Follow-up labs tell you whether the medication is working safely and whether anything needs attention.

These are the tests your provider should order before your first dose.

The CMP checks two critical organ systems:

• Kidney function: Creatinine and eGFR measure how well your kidneys are filtering waste. This matters because severe vomiting or diarrhea — common early side effects of semaglutide — can cause dehydration that stresses the kidneys.
• Liver function: ALT and AST are liver enzymes that establish a baseline. Semaglutide has been shown to reduce liver fat in many patients, but you want a starting point to compare against.

Order it here: Comprehensive Metabolic Profile

Semaglutide was originally developed as a diabetes medication. Even if you are taking it purely for weight loss, your provider needs to know your baseline glycemic status.

• HbA1c reflects your average blood sugar over the past 2–3 months and screens for prediabetes or diabetes.
• Fasting glucose gives a snapshot of your blood sugar after an overnight fast.

If you already have diabetes, these numbers are essential for adjusting other medications — particularly insulin or sulfonylureas — as semaglutide lowers blood sugar significantly.

Order it here: Hemoglobin A1c Test | Glucose Test

Semaglutide has a favorable effect on cholesterol in most patients — LDL and triglycerides tend to improve. But you need a baseline to see that improvement. A lipid panel measures:

• Total cholesterol
• LDL ("bad" cholesterol)
• HDL ("good" cholesterol)
• Triglycerides

Order it here: Basic Heart Health Panel

This one is important and often overlooked. Semaglutide carries a boxed warning regarding thyroid C-cell tumors observed in animal studies. The medication is contraindicated in anyone with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

A TSH test does not directly screen for thyroid cancer, but it establishes a thyroid baseline and helps identify any pre-existing thyroid dysfunction before starting treatment. If you want to go deeper on thyroid function, the Free T3 Test measures the active, unbound form of thyroid hormone that TSH alone can miss. The Comprehensive Health Panel also includes a full thyroid panel with TSH alongside metabolic and cardiovascular markers.

A CBC evaluates your red blood cells, white blood cells, and platelets. It rules out hidden infections, anemia, or immune abnormalities before you begin. It is also a useful general health marker to have on file.

Order it here: Complete Blood Count

Once you are on semaglutide, certain labs should be repeated at regular intervals.

Repeat the CMP periodically, especially during the dose escalation phase when nausea, vomiting, and diarrhea are most common. Dehydration from GI side effects is the most common reason kidney function declines on semaglutide. Catching it early prevents serious complications.

If you have diabetes or prediabetes, HbA1c should be checked every 3 months while your dose is being adjusted. Once stable, annually is typically sufficient for non-diabetic patients using semaglutide for weight loss.

Most patients see meaningful improvement in their lipid numbers within 6–12 months on semaglutide. An annual lipid panel lets you and your provider track that progress and adjust any cholesterol medications accordingly.

This is the most commonly missed category. Because semaglutide dramatically reduces appetite and food intake, nutritional deficiencies can develop over time. Key markers to check annually include:

• Vitamin B12 — reduced food intake and potential changes in gut motility can lower B12 levels
• Vitamin D — commonly deficient in overweight individuals; worth tracking as body composition changes
• Iron and Ferritin — reduced red meat and overall caloric intake can deplete iron stores

Order it here: Comprehensive Vitamin Panel | Vitamin B12 and Folic Acid | Ferritin Test

Here is a simple schedule to follow:

You do not need a prescription to order most of these tests. At Reliable Exams, you can order a CMP, HbA1c, lipid panel, CBC, and more directly — no doctor's visit required. Results are typically available within 1–2 business days from a LabCorp or Quest Diagnostics location near you.

Browse our full test catalog at reliableexams.com/tests or order the specific tests mentioned above directly.

This article is for informational purposes only and does not constitute medical advice. Always consult your prescribing provider before making changes to your medication or monitoring plan.