Baseline Labs and Health Markers to Check Before Starting a GLP-1

Written by Dan Cripe, RN, BSN & Marcia Cripe, RN | Last Updated: September 13, 2026

Before you start a GLP-1 medication, it is useful to know where your health stands.

That doesn't mean you need an enormous panel of specialty blood tests before your first injection. There is no single universal “GLP-1 lab panel” that every person must complete before starting semaglutide or tirzepatide.

What you need depends on why you're taking the medication, your medical history, other medications, and the conditions your clinician is already monitoring.

For many people, useful baseline information includes blood sugar status, kidney function, liver-related markers, lipids, blood pressure, weight, and sometimes additional testing based on symptoms or medical history. The 2026 Standards of Care in Overweight and Obesity include A1C, lipid testing, liver-related evaluation, serum creatinine/eGFR, blood pressure, weight, BMI, and other clinically indicated assessments as part of evaluating adults with overweight or obesity.

The purpose isn't to prove you're “healthy enough” to use a GLP-1.

It is to create a baseline. If your A1C, blood pressure, triglycerides, liver enzymes, or weight change six months from now, you'll know where you started.

What Blood Work Is Needed Before Ozempic or Another GLP-1?

There is an important difference between tests that are useful in the overall evaluation and tests that the medication itself requires before Dose 1.

Not everyone needs the same blood work.

A person with type 2 diabetes may need a more extensive diabetes assessment than someone without diabetes starting treatment for obesity. Someone with chronic kidney disease, hypertension, liver disease, thyroid symptoms, anemia, or another medical condition may need additional testing specific to that condition.

For a general metabolic baseline, your clinician may consider several common measurements.

A1C or another measure of blood glucose

A1C is particularly useful because it provides an estimate of recent average glucose exposure rather than a snapshot of your glucose at one moment.

If you already have diabetes, it provides a baseline against which treatment can later be compared. If you don't know your glycemic status, it can help identify previously unrecognized prediabetes or diabetes.

The ADA's 2026 obesity evaluation recommendations include A1C among laboratory assessments for obesity-related complications. Fasting plasma glucose is another established test for screening and diagnosing diabetes, and the appropriate test depends on the clinical situation.

Kidney function

Knowing your kidney function can be valuable before treatment, particularly if you already have kidney disease or take medications affected by kidney function.

Serum creatinine and estimated glomerular filtration rate, or eGFR, provide a baseline measure. The 2026 obesity standards include serum creatinine and eGFR in the clinical evaluation when considering obesity treatment.

This becomes particularly relevant if significant vomiting or diarrhea develops after starting treatment. GLP-1-related gastrointestinal symptoms can sometimes cause substantial fluid loss, which can affect kidney function.

Having a baseline gives your clinician something meaningful to compare against if that happens.

Liver-related testing

Obesity, insulin resistance, and type 2 diabetes are closely associated with metabolic dysfunction-associated steatotic liver disease, or MASLD.

Current obesity guidance includes AST, ALT, and platelet count as part of evaluation for liver-related complications, with those values also allowing clinicians to calculate FIB-4 when appropriate.

An abnormal liver enzyme does not automatically mean you cannot start a GLP-1. It may instead identify another metabolic condition worth evaluating and following.

Lipid profile

A baseline lipid panel can include total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides.

These numbers aren't necessary because a GLP-1 somehow requires normal cholesterol before you can use it. They are useful because cardiovascular and metabolic risk are part of the larger health picture, and weight treatment may occur alongside treatment of dyslipidemia, hypertension, diabetes, or cardiovascular disease.

The 2026 obesity standards specifically include lipid-profile assessment when evaluating obesity-related disease and complications.

Essential Metabolic Panels: A1C, Fasting Insulin, and CMP

You may see online GLP-1 lab checklists recommending A1C, fasting insulin, and a comprehensive metabolic panel—CMP—for everyone.

That overstates the evidence.

A1C is an established measure for assessing glycemic status. A CMP can provide useful information about glucose, electrolytes, kidney-related markers, liver enzymes, and other measures, depending on the panel used.

Fasting insulin is different.

It can be ordered in particular clinical situations, but routine fasting insulin testing is not a standard requirement before starting a GLP-1 medication. Current obesity evaluation recommendations emphasize established measures such as A1C or glucose for glycemic assessment rather than requiring fasting insulin as part of a universal baseline panel.

That distinction matters because more testing isn't automatically better testing.

If your clinician has a specific reason to measure fasting insulin, that's different. But you shouldn't conclude that your pre-treatment workup is incomplete simply because it wasn't ordered.

What About a CBC, Vitamin D, B12, Iron, and Ferritin?

These can be useful tests for the right person, but they aren't universal GLP-1 requirements either.

The 2026 obesity standards include assessment of vitamin and mineral status when indicated, with examples including vitamin D, vitamin B12, iron, and ferritin.

That “when indicated” matters.

If you already have fatigue, anemia, heavy menstrual bleeding, a restrictive diet, previous bariatric surgery, nutritional deficiencies, or another reason to suspect a deficiency, your clinician may reasonably investigate further.

A CBC can similarly be useful when there is a clinical reason to evaluate anemia, infection, blood-cell abnormalities, or another condition.

But you don't need to turn starting a GLP-1 into a scavenger hunt for every laboratory value that can possibly be measured.

Endocrine Screening: TSH and Calcitonin Considerations

Thyroid testing creates particular confusion because semaglutide and tirzepatide products carry boxed warnings related to thyroid C-cell tumors observed in rodents.

That does not mean everyone needs an extensive thyroid blood panel before treatment.

Should you have a TSH before Wegovy?

TSH evaluates thyroid function. It can help identify hypothyroidism or hyperthyroidism, but it is not a test for medullary thyroid carcinoma.

The 2026 obesity standards recommend TSH when clinically indicated—for example, when symptoms suggest hypothyroidism or a secondary endocrine contributor to weight gain is being considered—rather than requiring it for every person with obesity.

In practice, your clinician may already have a recent TSH or may choose to obtain one as part of your broader evaluation.

But TSH is not a special safety test that clears you to take Wegovy.

What about calcitonin?

Calcitonin is associated with thyroid C cells and can be elevated in medullary thyroid carcinoma, which makes it sound like an obvious screening test before a GLP-1.

The prescribing information is more nuanced.

GLP-1 medications including semaglutide and tirzepatide carry warnings based on thyroid C-cell tumors seen in rodent studies, and these products are contraindicated in people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2.

However, routine serum calcitonin measurement or thyroid ultrasound for early detection of medullary thyroid carcinoma has uncertain value according to prescribing information.

That means your medical history matters enormously.

Tell your prescriber about a personal or family history of medullary thyroid carcinoma or MEN2 and about concerning thyroid symptoms or a neck mass. Don't assume that a normal TSH—or a random normal calcitonin level—substitutes for that history.

Your Medical History Is Part of the Baseline Too

Some of the most important pre-GLP-1 information will never appear on a blood test.

Your prescriber needs an accurate medication list and relevant medical history.

That includes previous pancreatitis, gallbladder problems, kidney disease, significant gastrointestinal disease or symptoms, diabetes and diabetes complications, and medications that may need adjustment as glucose or blood pressure changes.

Pregnancy status and plans for pregnancy also matter. For people who could become pregnant, this deserves a direct conversation rather than being buried in a generic lab checklist.

Your clinician should also know whether you use insulin or a sulfonylurea because combining these medications with a GLP-1-based treatment can increase the risk of hypoglycemia and may affect the treatment plan.

If you have diabetes, the baseline evaluation can extend beyond laboratory testing. Diabetes care may include assessment of kidney disease, retinopathy, neuropathy, cardiovascular risk, and other complications depending on your individual situation.

Should You Get a DEXA Scan Before Zepbound?

You don't need a DEXA scan simply because you're starting Zepbound.

But there is a reasonable argument for obtaining a body-composition baseline if knowing your lean mass and fat mass would meaningfully change how you monitor treatment.

A standard bathroom scale tells you total body weight. It cannot tell you how much of that weight is fat, lean tissue, bone, water, or other body mass.

DEXA—dual-energy X-ray absorptiometry—can provide estimates of body composition, including fat and lean mass, in addition to its established use for measuring bone mineral density.

This can be useful because substantial weight loss does not consist exclusively of body fat. Some lean mass loss occurs during weight reduction as well.

But DEXA is not mandatory GLP-1 monitoring.

Current diabetes guidance increasingly recognizes that BMI alone does not completely characterize adiposity. The ADA's 2026 revisions recommend incorporating an additional assessment of body fat, using anthropometric or direct measurements, when available and feasible.

That does not mean everyone needs an expensive scan.

Waist circumference, body measurements, strength and physical-function measures, and appropriately interpreted body-composition tools can all add information beyond the number on the scale.

If you do choose DEXA specifically to follow body composition, the value comes from having a baseline that can later be compared using reasonably consistent conditions and methodology, not from collecting one scan and never repeating it.

A Strength Baseline May Be More Useful Than You Think

Body composition isn't the only way to monitor what you're preserving during weight loss.

Before starting treatment, consider documenting what your body can actually do.

That might mean the resistance you're currently using for several major exercises, how many controlled sit-to-stands you can perform, your usual walking pace, or another simple measure that is appropriate for your physical abilities.

This doesn't replace medical testing.

It answers a different question.

A DEXA scan may tell you whether estimated lean mass changed. A strength or function measure tells you whether you're maintaining your ability to use that tissue.

If you're planning substantial weight loss, both nutrition and resistance training deserve attention from the beginning rather than waiting until you've already lost a significant amount of weight.

Establish a Weight and Waist Baseline

Record your starting weight before treatment, but don't make it the only measurement you collect.

If you're comfortable doing so, waist circumference can provide another useful marker of change in central adiposity. Current obesity evaluation standards include height, weight, BMI, and waist-related measurements when appropriate.

Consistency matters more than creating a perfect ritual.

If you're going to compare weights over time, use the same scale under reasonably similar conditions. If you're measuring your waist, use the same anatomical location and technique each time.

You don't need daily measurements of everything.

You need a baseline reliable enough that future changes actually mean something.

Vitals to Monitor Weekly at Home

Blood pressure deserves attention because successful weight treatment can change it.

If you already have hypertension or take blood-pressure medication, home monitoring can become particularly useful as treatment progresses. Current obesity evaluation guidance includes blood pressure and heart rate among baseline vital signs.

For someone whose clinician wants home monitoring, a simple weekly record might include:

1. Blood pressure. Measure it using a properly fitting upper-arm cuff and consistent technique. If you're taking antihypertensive medication, your clinician may want more frequent readings as weight changes.
2. Heart rate. Record your resting pulse when you check your blood pressure. GLP-1 medications can produce small increases in resting heart rate in some people, and product labeling contains medication-specific monitoring information.
3. Weight. Weekly weighing is enough to establish a useful trend for many people. Daily weighing is optional, not a requirement for successful treatment.

You don't need to create a medical command center in your bathroom.

The purpose of monitoring is to detect meaningful trends.

If you're becoming lightheaded when standing, unusually weak, or symptomatic while your blood pressure is falling, don't simply celebrate the lower number. Contact the clinician managing your blood-pressure medications because treatment may need to be reassessed.

What Should You Actually Record Before Dose 1?

This is one situation where a concise baseline checklist is useful because you're collecting information rather than explaining a mechanism.

Before your first dose, consider documenting:

1. Current weight and BMI, with waist circumference if you're planning to track it.
2. Blood pressure and resting heart rate, particularly if you have hypertension or take cardiovascular medications.
3. A1C or other appropriate glucose testing if your clinician recommends it.
4. Kidney function, typically including creatinine and eGFR when indicated as part of your metabolic evaluation.
5. Lipid profile to establish your cardiovascular risk baseline.
6. Liver-related markers when appropriate, particularly in the context of metabolic disease or possible MASLD.
7. Additional labs based on your history, which may include TSH, CBC, vitamin B12, vitamin D, iron studies, or other targeted testing.
8. Your medication list and relevant medical history, including diabetes medications, blood-pressure medications, kidney or gallbladder disease, previous pancreatitis, and relevant thyroid cancer history.
9. Optional body-composition or strength measurements if you intend to follow muscle preservation during substantial weight loss.

You may already have most of this information from routine medical care.

If you had appropriate laboratory testing recently, starting a GLP-1 does not automatically mean every test needs to be repeated simply to create a new “Day 0” panel.

Don't Turn Baseline Testing Into a Barrier to Starting

There is a risk at the other extreme: seeing elaborate GLP-1 laboratory checklists online and believing you cannot start treatment until you've obtained 20 different biomarkers, a DEXA scan, thyroid ultrasound, fasting insulin, vitamin panels, and specialty hormone testing.

That's not what the evidence supports.

Baseline evaluation should answer useful clinical questions.

Do you have diabetes or prediabetes? What is your kidney function? Are there metabolic complications that should be monitored? Do your symptoms suggest a thyroid or other endocrine disorder? Are there nutritional deficiencies or medical conditions that need attention? Are there medications that might need adjustment as treatment progresses?

Those questions are much more useful than ordering every available test.

Your baseline should be individualized enough to identify relevant risks and simple enough that you can actually use it later.

The Real Value Comes From Comparing Later

A baseline measurement is valuable because it gives future measurements context.

Six months from now, losing 30 pounds tells you something.

Knowing that your weight decreased while your A1C moved from one level to another, your blood pressure improved, your triglycerides changed, your waist circumference decreased, and your strength remained stable tells you considerably more.

It also helps separate health improvement from weight loss alone.

The scale may eventually slow down even while metabolic markers continue improving. Conversely, rapid weight loss doesn't automatically guarantee that every health marker is moving in the right direction.

That is why the best baseline isn't the longest list of laboratory tests you can order.

It is a thoughtful snapshot of the things that matter for your health before treatment changes them.

Sources

1. American Diabetes Association Professional Practice Committee for Obesity. Screening, Diagnosis, Evaluation, and Staging of Obesity in Adults: Standards of Care in Overweight and Obesity—2026. Diabetes, Obesity, and Cardiometabolic CARE. 2026.
   https://diabetesjournals.org/docm-care/article/1/4/536/170058/Screening-Diagnosis-Evaluation-and-Staging-of
2. American Diabetes Association Professional Practice Committee. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026. Diabetes Care. 2026.
   https://diabetesjournals.org/care/article/49/Supplement_1/S27/163926/2-Diagnosis-and-Classification-of-Diabetes
3. American Diabetes Association Professional Practice Committee. Comprehensive Medical Evaluation and Assessment of Comorbidities: Standards of Care in Diabetes—2026. Diabetes Care. 2026.
   https://diabetesjournals.org/care/article/49/Supplement_1/S61/163931/4-Comprehensive-Medical-Evaluation-and-Assessment
4. American Diabetes Association Professional Practice Committee. Summary of Revisions: Standards of Care in Diabetes—2026. Diabetes Care. 2026.
   https://diabetesjournals.org/care/article/49/Supplement_1/S6/163930/Summary-of-Revisions-Standards-of-Care-in-Diabetes
5. Novo Nordisk. Wegovy (semaglutide) Prescribing Information.
   https://www.novo-pi.com/wegovy.pdf
6. Novo Nordisk. Ozempic (semaglutide) Prescribing Information.
   https://www.novo-pi.com/ozempic.pdf
7. Eli Lilly and Company. Zepbound (tirzepatide) Prescribing Information.
   https://pi.lilly.com/us/zepbound-uspi.pdf