Before starting semaglutide (sold as Ozempic or Wegovy), you’ll typically need a set of baseline blood tests covering blood sugar, liver function, kidney function, thyroid health, and cholesterol levels. The exact panel varies by prescriber, but these five categories form the clinical standard. Your provider uses these results both to confirm you’re a safe candidate and to create a baseline for tracking how your body responds over time.
Blood Sugar Tests
Two markers give your prescriber a picture of your glucose metabolism. HbA1c reflects your average blood sugar over the past two to three months, while fasting blood glucose captures your level after an overnight fast. Together, they show whether you have diabetes, prediabetes, or normal glucose control.
These matter regardless of why you’re taking semaglutide. If you’re using it for weight loss without a diabetes diagnosis, semaglutide still lowers blood sugar, and your provider needs to know your starting point to watch for levels dropping too low. The FDA prescribing information for Wegovy specifically requires blood glucose monitoring before and during treatment for patients with type 2 diabetes.
Liver Function Panel
Your liver processes medications and plays a central role in fat metabolism, so prescribers check several liver markers before starting treatment. The key ones are ALT and AST, two enzymes that rise when liver cells are damaged. GGT, a third enzyme sensitive to bile duct problems and liver inflammation, is often included as well. Albumin rounds out the panel. It’s a protein your liver produces, and low levels can signal poor liver function or nutritional deficiency.
Rapid weight loss can stress the liver, and semaglutide also increases the risk of gallbladder problems (gallstones in particular). Having a clear baseline lets your provider distinguish between a pre-existing liver issue and something that develops during treatment.
Kidney Function Markers
Kidney tests center on two values: creatinine (a waste product your kidneys filter out) and eGFR, which is calculated from your creatinine level and gives the best overall measure of how well your kidneys are working. Some panels also include urea, another waste product the kidneys excrete.
Semaglutide commonly causes nausea, vomiting, and diarrhea, especially during the first weeks and after each dose increase. These side effects can lead to dehydration, which puts extra strain on the kidneys. The FDA label instructs providers to monitor kidney function in patients experiencing side effects that could cause fluid loss. Clinicians at Cleveland Clinic recommend reassessing patients one month after starting and then every three months once you’re on a stable dose, with particular attention to eGFR and urine albumin levels.
If your kidneys are already impaired, your provider will track a urine test called the albumin-to-creatinine ratio. A significant jump in that number, especially above 30 mg/g alongside a falling eGFR, is a signal to involve a kidney specialist.
Thyroid Function Tests
A standard thyroid screen includes TSH (the hormone that regulates your thyroid) and free T4 (the main thyroid hormone circulating in your blood). These establish whether your thyroid is overactive, underactive, or normal before treatment begins.
Thyroid testing gets extra attention with semaglutide because of a specific safety concern. In animal studies, GLP-1 drugs caused a type of thyroid cancer called medullary thyroid carcinoma in rodents. That finding led the FDA to add a boxed warning: semaglutide should not be used by anyone with a personal or family history of medullary thyroid cancer or a condition called MEN2 (multiple endocrine neoplasia type 2). A baseline thyroid panel helps flag undiagnosed thyroid problems before you start.
You might wonder whether you need a calcitonin blood test or thyroid ultrasound for ongoing screening. Current evidence suggests you don’t. The FDA prescribing information states that routine calcitonin monitoring “is of uncertain value” and may lead to unnecessary procedures because of high false-positive rates. A recent analysis highlighted by Mayo Clinic found that the apparent link between GLP-1 drugs and thyroid cancer in humans appears to be detection bias, not a true causal relationship. If a thyroid nodule happens to be found while you’re on semaglutide, it should be treated as a likely incidental finding and worked up using standard guidelines.
Lipid Panel
A lipid panel measures your total cholesterol, HDL (“good”) cholesterol, non-HDL cholesterol, and triglycerides. Some comprehensive panels also include ApoB, a direct count of the particles that contribute to artery plaque buildup. This test is increasingly considered a better predictor of cardiovascular risk than LDL alone.
Semaglutide typically improves lipid numbers as weight drops, particularly triglycerides. Having pre-treatment values lets your provider quantify those improvements and decide whether to adjust any cholesterol medications you might be taking. Quest Diagnostics notes that lipid testing during treatment helps measure how weight loss is reducing your chronic disease risk over time.
Additional Markers Some Providers Order
Beyond the five core categories, many prescribers add a few extra tests to create a more complete picture:
- Complete blood count (CBC): Checks red blood cells, white blood cells, hemoglobin, and platelets. It catches anemia, infection, and other conditions that could complicate treatment.
- CRP (C-reactive protein): A general measure of inflammation in the body. Semaglutide has been shown to reduce systemic inflammation, so a baseline value helps track that change.
- Vitamin D: Important for bone health and immune function. Rapid weight loss can affect nutrient absorption, and many people are already deficient before starting treatment.
- Iron and ferritin: Ferritin measures your stored iron, while serum iron reflects what’s currently circulating. Reduced food intake on semaglutide can worsen an existing iron deficiency.
These aren’t universally required, but they’re common enough that you shouldn’t be surprised to see them on your lab order.
What About Pancreatic Enzymes?
Semaglutide carries a warning about pancreatitis (inflammation of the pancreas), which raises the question of whether amylase and lipase levels should be checked routinely. These two enzymes spike dramatically during an acute pancreatitis episode.
Routine screening of these enzymes in patients without symptoms isn’t standard practice, but some clinics do it anyway as a precaution. One outpatient study tracked patients on GLP-1 drugs every three to four months and found that while some developed elevated lipase levels, none of them had symptoms or required hospitalization. The elevations typically returned to normal after stopping the medication. Checking a baseline gives your provider a reference point if you ever develop unexplained abdominal pain during treatment, which is the symptom that genuinely warrants urgent pancreatic enzyme testing.
Follow-Up Lab Schedule
Your first round of follow-up labs typically happens four to six weeks after starting semaglutide, then shifts to every three months once you’re on a stable dose. This schedule aligns with the dose escalation period, which takes about 16 to 20 weeks as you gradually increase from the starting dose to the maintenance dose.
Follow-up panels generally repeat the same core tests: blood sugar, kidney function, liver enzymes, and lipids. Your provider is looking for two things at each check: safety signals (kidney function declining, liver enzymes climbing) and treatment response (HbA1c dropping, cholesterol improving, inflammation decreasing). Once your labs are stable and you’ve been at your maintenance dose for several months, some providers extend the interval to every six months.