What Labs Should I Get Before Starting a GLP-1?

Before starting semaglutide, tirzepatide or another GLP-1, the core blood tests are HbA1c or fasting glucose, a comprehensive metabolic panel (kidney and liver function) and a lipid panel, along with your waist size, blood pressure and resting heart rate. A thyroid test or hormone tests are added when your health history calls for them. The most important safety check is not a blood test at all. It is whether you or anyone in your family has had medullary thyroid cancer or a condition called MEN 2.

The core set is the same for every woman. Anything beyond it depends on your history, and the table below shows which tests fit your situation. You can order the core tests yourself for under $150.

Which blood tests do I need before starting a GLP-1?

A 2026 expert consensus on incretin medicines lists the same starting checks for everyone. Some of them you can do at home.

• Fasting glucose and HbA1c. HbA1c is your average blood sugar over about the last three months.
• A lipid panel. This gives you your cholesterol numbers.
• Liver function tests.
• Kidney function. This means creatinine and eGFR, which estimate how well your kidneys filter.
• Thyroid function, only when there is a clinical reason. Most women won't need it.
• One blood draw for several of these. A comprehensive metabolic panel (CMP) measures blood sugar, electrolytes and markers of liver and kidney function. In practice, HbA1c, a CMP and a lipid panel cover the core blood work.
• Waist, blood pressure and heart rate. You can measure all three at home. Heart rate matters because the Wegovy prescribing information lists a faster heart rate among its warnings, so a starting number gives you something to compare against.
• Optional extras some clinicians like to see. The Obesity Medicine Association lists TSH (the standard thyroid screen), a complete blood count, urine microalbumin (a kidney check) and sometimes vitamin D.

Do I need labs before I can get a GLP-1 prescription?

Not always. The check that matters most is a question about your history. Semaglutide's label rules it out if you or a family member has had medullary thyroid carcinoma (MTC), or if you have MEN 2. No blood test can clear you of that, so your answer to that question carries more weight than any lab result.

A calcitonin test or thyroid ultrasound is not a standard pre-check either. The same label says routine calcitonin or ultrasound monitoring is of uncertain value for catching MTC early and may lead to unnecessary procedures.

Telehealth programs set their own lab rules. A 2026 comparison of six telehealth GLP-1 programs found that Walgreens allowed a first prescription with no labs and Mochi said labs are never required. PlushCare ordered labs before prescribing.

Our view is to get the core baseline anyway. Whether a program asks for labs is a separate question from whether you want your own before and after numbers. Without them, the scale is the only result you'll be able to see.

Which extra labs should I get for my health history?

Find the rows that match you. If none do, the core set above is your list.

What can my baseline labs show once I'm on a GLP-1?

Your starting numbers show changes the scale can't. In Wegovy's heart outcomes trial of adults with heart disease and overweight or obesity, HbA1c fell 0.3 points more than on placebo. Systolic blood pressure fell 3.8 mmHg, compared with 0.5 mmHg on placebo. If you know where you started, you can see those changes in your own results.

Your liver numbers are worth a baseline too. In Wegovy's MASH trial, average ALT and AST fell further than on placebo from week 12 through week 72.

Tirzepatide and retatrutide have their own liver results. In a phase 2a trial of 98 adults with obesity and fatty liver, retatrutide cut liver fat on MRI by 51% to 86% at 48 weeks, depending on dose. On placebo, liver fat fell 4.6%. In the SYNERGY-NASH trial, MASH cleared without worse scarring in 44% to 62% of people on tirzepatide (5 to 15 mg), compared with 10% on placebo. No trial has compared these drugs head to head for the liver. Your clinical team can match the medicine to your numbers and your goal.

One woman's long-term numbers show why this matters. A 65-year-old woman on compounded tirzepatide wrote that she was "on 15mg/wk for 3+ years with AIC initially dropped from 6.8, then stabilized within range of 5.8-6.1." Without her starting number, she couldn't have tracked that change.

How much do GLP-1 blood tests cost without insurance?

The core set costs under $150 if you order it yourself. Through Labcorp OnDemand, you can buy lab tests online without a doctor's visit. Most results are ready within 1 to 2 days after your sample reaches the lab.

Ordered separately, HbA1c, a CMP and a lipid panel come to $132.25 at the sale price for the lipid panel, or $147 at the regular price. If your history calls for a thyroid check, the standard thyroid test adds $89.

If you've had blood work in the last few months, bring those results to your clinical team instead of paying twice. Ask them which extras your history needs.

Then take the quiz to tell our clinical team about your goal, your health history and any recent labs, and see which GLP-1 plan (semaglutide, tirzepatide or retatrutide) fits you.