The GLP-1 Testing Gap: Why Millions on Weight-Loss Drugs Aren’t Watching What’s Happening Inside Their Bodies

By Robert Distefano

Roughly 40 million Americans are now taking a GLP-1 medication for weight loss, a jump from just 3% of the population in 2024 to 11% today, according to Gallup’s June 2026 polling. Names like Semaglutide and tirzepatide have become part of everyday vocabulary, and while the drugs are delivering real results on the scale, most people taking them have no idea what else is changing inside their bodies while they’re on it.

The Blind Spot Behind the Boom

GLP-1 drugs do more than just suppress appetite. They can also accelerate muscle loss, shift thyroid and metabolic function, alter hormone levels, and, over time, contribute to nutrient deficiencies as intake drops, none of which will show up on your bathroom scale. The only way to know is bloodwork, and that’s exactly where most damage passes through unseen.

Ordering labs typically means booking a doctor’s appointment, getting a referral, waiting for insurance approval, and then waiting again for an opening and if you’re already managing a new medication, a new eating pattern, and a new relationship with their appetite, that pushes it just far enough into the inconvenient corner to become irrelevant. Most people start a GLP-1 with a single baseline panel, if that, and don’t test again until something feels wrong.

What GLP-1 Users Should Actually Be Tracking

Health experts monitoring the GLP-1 boom point to a handful of biomarkers that matter most for people on these medications:

• Muscle mass and lean tissue markers. Rapid weight loss on GLP-1s can include significant lean muscle loss alongside fat loss, which affects metabolism, strength, and long-term weight maintenance.
• Micronutrients. Reduced food intake means a higher risk of falling short on B12, iron, vitamin D, and other nutrients that support energy and immune function.
• Thyroid panels. Metabolic shifts on GLP-1s can interact with thyroid function, making regular monitoring worthwhile, particularly for anyone with a personal or family thyroid history.
• Metabolic markers, including blood glucose, insulin, and lipid panels, to track how the medication is actually reshaping metabolic health, not just body weight.
• Hormone levels, which can shift as body composition changes and may affect everything from energy to mood to menstrual cycles.

While this information alone isn’t the same as asking your doctor it does mean that testing shouldn’t be a one-time event at the start of treatment, but ongoing, and it should be easy enough that people actually do it.

The stakes are highest for people who stay on these medications long-term. GLP-1s were originally developed for chronic conditions like type 2 diabetes, and many patients are now expected to remain on them for years, not months. Subjecting your body to such long periods in a suppressed-appetite, rapid-change state needs more oversight than a single blood draw at the start, yet most insurance plans still treat lab work as an occasional, doctor-gated event rather than a routine part of managing a long-term prescription.

Why Direct-Access Testing Is Having a Moment

That’s the opening that direct-access lab testing has stepped into. Companies offering consumer-ordered bloodwork, without a physician’s referral or insurance pre-approval, have grown alongside the GLP-1 boom due to people wanting to check in on their bodies more often than the traditional system makes convenient.

Josh Reinitz and Robert Distefano saw that gap firsthand and built TestWell to close it. The platform lets anyone order their own lab work directly, with no doctor’s note and no insurance required, at up to 80% less than typical lab pricing. Every test is processed through major national labs, including Quest, LabCorp, and BioReference, and available in 49 states.

“People are turning to AI more and more as a starting point for their health questions, and the natural next step is getting real data to back that up,” said Robert Distefano, co-founder of TestWell. “Instead of waiting weeks for an appointment just to ask for a basic panel, we wanted to give people the same access a doctor has, at a price that actually makes sense.”

Customers can build a fully custom panel, choosing exactly which tests they want, or use TestWell’s AI-powered lab agent, which recommends a panel based on age, weight, health history, and specific concerns, then helps translate the results afterward. For someone on a GLP-1 who wants to check thyroid function, muscle-related markers, and micronutrient levels in one order, that’s a great way to skip the referral process entirely.

Monitoring as Part of the Plan, Not an Afterthought

The rise of GLP-1s has been framed largely as a story about weight, but the more important story may be what happens to the rest of the body while that weight comes off. As usage climbs toward record levels, biomarker testing is emerging as a natural complement to treatment rather than an optional extra.

Direct-access platforms like TestWell are part of a broader shift toward people managing more of their own healthcare decisions, informed by data they can get without the usual delays. For GLP-1 users, that shift may matter most. A medication that changes so much about the body deserves more than a single baseline test and a hope that everything else stays on track.

As more physicians and researchers weigh in on long-term GLP-1 monitoring, expect direct-access testing to keep gaining ground as the missing piece that makes ongoing monitoring realistic for the millions of Americans now on these drugs.

 

Robert Distefano is a co-founder of TestWell. He lead growth and strategy for the business, driving Google Search campaigns working with affiliate and ambassador channels, and shaping the company’s approach to content and brand positioning. He works closely with his co-founder, who focuses on content creation, and brings sharp product instincts to the table.