Weight Loss & GLP-1 Blood Tests

Whether you’re starting a GLP-1 medication like Ozempic, Wegovy, or Mounjaro, training for a competition, or trying to lose weight the right way — blood work is the foundation of every successful weight management plan.

Blood tests reveal hidden causes of weight gain including thyroid dysfunction, insulin resistance, low testosterone, vitamin D deficiency, and hormonal imbalances. Identify what’s working against you so you can fix the root cause instead of guessing.

Starting a GLP-1? Your baseline panel should include a CMP ($44), A1c ($39), Thyroid Panel ($69), Lipid Panel ($44), CBC ($34), and Vitamin D ($59). Read our complete guide: Blood Tests Before and During GLP-1 Treatment

Trying to lose weight without medication? Start with a Thyroid Panel — hypothyroidism is the #1 hidden cause of unexplained weight gain. Add an A1c to check for insulin resistance and Testosterone for men experiencing fat gain and muscle loss.

Bodybuilder or athlete? Check out our Bodybuilder Blood Test Panel or read our TRT Blood Work Guide.

All tests include a physician-approved lab order. No doctor visit, no insurance needed. HSA and FSA eligible.

Why Muscle Preservation Testing Matters on GLP-1 Medications

GLP-1 medications like Ozempic, Wegovy, and Mounjaro are highly effective for
weight loss — but clinical studies show that 25–40% of weight lost on GLP-1s
can come from lean muscle mass, not just fat. This is called GLP-1-induced
muscle loss, and it’s one of the most underreported risks of these medications.

Monitoring the right biomarkers while on a GLP-1 helps you and your provider
ensure you’re losing fat — not muscle. The key markers to track are:

Albumin and Total Protein (from a CMP) — declining levels can indicate
inadequate protein intake and muscle breakdown. A CMP also monitors kidney
and liver function, both of which are affected by significant rapid weight loss.

Testosterone (men) — GLP-1-related caloric restriction can suppress testosterone
production, accelerating muscle loss and causing fatigue, reduced libido, and
strength decline. Men on GLP-1s should test testosterone every 3–6 months.

Vitamin D — deficiency impairs muscle protein synthesis and is extremely common
in overweight individuals. Correcting Vitamin D before and during GLP-1 treatment
supports muscle retention and bone density.

Complete Blood Count (CBC) — rapid weight loss can affect red blood cell
production. CBC monitors for anemia, which causes the fatigue many GLP-1 users
report and incorrectly attribute to the medication itself.

The Personalabs Weight Loss Profile bundles the most critical monitoring markers
into a single affordable panel — designed specifically for people on or considering
GLP-1 medications.

Reviewed by Edward Salko, D.O., Medical Director, Personalabs

Frequently Asked Questions: Weight Loss & GLP-1 Blood Tests

What blood tests do I need before starting Ozempic or Wegovy?

Before starting a GLP-1 medication like Ozempic or Wegovy, most providers
recommend a baseline panel including: HbA1c (blood sugar control), CMP (kidney
and liver function), Lipid Panel (cholesterol), CBC (blood health), Thyroid
Panel (TSH), and Vitamin D. These tests confirm you are a safe candidate for
GLP-1 therapy and establish a baseline to measure your progress against.

Can GLP-1 medications cause muscle loss?

Yes. Clinical studies show that 25 to 40 percent of weight lost on GLP-1
medications like Ozempic and Wegovy can come from lean muscle mass rather than
fat. Monitoring albumin, total protein, testosterone (in men), and Vitamin D
levels during treatment helps identify early signs of muscle breakdown so you
can adjust protein intake before significant loss occurs.

How often should I get blood work while on Ozempic or Mounjaro?

Most GLP-1 prescribers recommend baseline blood work before starting, a
follow-up panel at 3 months to check HbA1c improvement and kidney function,
and a full panel repeat at 6 months. Men experiencing fatigue or muscle loss
should add testosterone testing at each interval. Personalabs makes it easy
and affordable to stay on this schedule without waiting for a doctor’s
appointment.

What is the best blood test panel for weight loss?

The most comprehensive weight loss blood test panel should include a Thyroid
Panel — hypothyroidism is the number one hidden cause of unexplained weight
gain — plus HbA1c for insulin resistance screening, a CMP for metabolic
function, a Lipid Panel for cardiovascular risk, Testosterone for men, and
Vitamin D. Order individually or as a bundled panel at Personalabs — no
doctor visit required.