DEXA Scan on GLP-1 (Ozempic, Wegovy, Mounjaro, Zepbound): Track Fat vs Muscle Loss
Updated October 25, 2026 · Research summarized from the STEP 1 and SURMOUNT-1 trials
Quick answer: A bathroom scale can't tell you what you're losing on a GLP-1 medication. In clinical trials, a large share of the weight lost on semaglutide and tirzepatide was lean mass, not fat. A DEXA scan measures fat, lean muscle and bone separately in about 10 minutes, so you and your prescriber can see whether you're keeping your muscle. Scan before or soon after you start, then every 8 to 12 weeks. Tests on DEXASCAN.COM are HSA/FSA eligible and need no referral.
Why weight alone is misleading on a GLP-1
GLP-1 medications such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) produce large weight losses. But body weight includes fat, muscle, water and bone. In the STEP 1 trial, a DEXA substudy found that roughly 39% of the tissue participants lost on semaglutide was lean mass. In the SURMOUNT-1 trial, about a quarter of the weight lost on tirzepatide was lean mass. Losing some lean mass is expected with any large weight loss. How much you lose depends on protein intake, strength training and dose, and only a body composition test shows you which way you're trending.
What a DEXA scan shows
- Fat mass and body fat %, total and by region (arms, legs, trunk)
- Lean mass, so you can see whether you're keeping muscle
- Visceral fat, the deep belly fat most linked to metabolic risk
- Bone density, which can change with rapid weight loss
Add an RMR (resting metabolic rate) test to see how many calories you burn at rest. This helps when planning meals as your appetite changes. Compare methods on DEXA vs other body fat tests.
When to scan
Before your first dose or as soon as possible after starting, so you have a starting point.
Rescan at the same location while your dose is changing to see fat versus lean loss.
Scan when you reach maintenance or reduce your dose, to protect what you've gained.
Using your results
Share your DEXA report with your prescriber or coach. If your lean mass is dropping quickly, they may recommend changes to protein intake, resistance training or dosing. Track every scan in the free DEXASCAN app to see the trend over time. DEXASCAN.COM does not prescribe medication; talk to your healthcare provider about your treatment.
For GLP-1 clinics and telehealth programs
Want your patients to have body composition data? DEXASCAN.COM works with GLP-1 programs on co-branded scan offers and vouchers at locations nationwide. Partner with DEXASCAN.COM.
Book a baseline DEXA scan
Find a DEXA location near you with upfront pricing. HSA/FSA eligible, no referral needed.
Sources
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384:989-1002
- Look M et al. Body composition changes during weight reduction with tirzepatide in SURMOUNT-1. Diabetes Obes Metab. 2025;27:2720-2729
This page is for general information and is not medical advice. Ozempic, Wegovy, Mounjaro and Zepbound are trademarks of their owners; DEXASCAN.COM is not affiliated with them.
Frequently asked questions
Do you lose muscle on Ozempic, Wegovy or Zepbound?
Some lean mass loss is common with any large weight loss. In the STEP 1 DEXA substudy roughly 39% of the tissue lost on semaglutide was lean mass, and in SURMOUNT-1 about 25% of the weight lost on tirzepatide was lean mass. A DEXA scan shows how much of your own loss is fat versus lean mass.
How often should I get a DEXA scan on a GLP-1?
Get a baseline scan when you start, then rescan every 8 to 12 weeks at the same location, and again when you reach maintenance or taper your dose.
Do I need a referral for a DEXA scan?
No. Body composition DEXA scans booked on DEXASCAN.COM do not require a referral.
Can I use my HSA or FSA?
Yes. DEXA, VO2 Max and RMR tests booked on DEXASCAN.COM are HSA/FSA eligible. Pay with your HSA/FSA card at checkout or submit your receipt to your plan for reimbursement.
Is a DEXA scan better than a smart scale for tracking GLP-1 progress?
Yes. Smart scales estimate body fat with bioimpedance, which shifts with hydration. DEXA measures fat, lean mass and bone directly and is the method used in the GLP-1 clinical trials.