Nearly every Missouri med spa that answered a university phone survey said it was affiliated with a physician: 94.59%. Only 22.52% said a physician was on site while all cosmetic services were being administered. The same paper carries something rarer, a count of the medical spa services offered across one state.

The study, "Pulling Back the Curtain: A Cross-Sectional Analysis of Medical Spas in Missouri," ran in Dermatologic Surgery in January 2025. Its four authors, Amanda M. Ferrante, Ali M. Malik, M. Laurin Council and Basia M. Michalski-McNeely, are in the Division of Dermatology at Washington University School of Medicine in St. Louis. We read the full five-page text.

How it was done

There is no official list of med spas in Missouri. The authors tried to get one from state government, including the attorney general's office, and report that they could not because the state has no registration requirement. So they built one from Google searches in September 2023 and phoned each spa with a scripted survey.

Of 238 spas identified, 105 completed every part of the phone survey. That is 44% by our arithmetic. Seventeen declined at least one question, 11 of them all questions, and one spa was dropped for inconsistent answers. The whole-sample phone percentages work out to a base of 111, which fits the 105 plus six partial responders, though the paper doesn't spell that out.

Separately, the team reviewed 229 spa websites for additional services, weight loss and IV therapy among them.

What the spas sell

Among participating spas, 87.39% (97) reported offering botulinum toxin and 86.49% offered hyaluronic acid fillers. Microneedling was the most common service reported, at 92.79%. Laser, light or energy-based services were offered by 87.39%, led by laser hair removal at 72.97%.

The website review is where the adjacent lines show up. The paper reports that 53.07% of sites advertised some form of medical weight loss and 21.49% (49 sites) GLP-1 agonists. IV infusions appeared on 32.46% and B12 injections on 39.47%. Several of those percentages don't divide exactly from the counts printed beside them (49 of 229 is 21.40%), so treat the decimals as soft; the gaps run to about 0.3 of a point.

Who does the work

Mid-level staff, which the paper defines as nurses and nurse practitioners, injected neurotoxin at 94.68% of the spas offering it. Physicians injected at 18.09% and aestheticians at 2.13%. Fillers looked the same. Not so lasers and microneedling: aestheticians operated lasers at 67.42% of spas offering them and performed microneedling at 67.68%, with physicians at 12.36% and 5.05%.

The average spa had 1.18 affiliated physicians and 4.06 non-physician staff administering cosmetic services, a ratio the authors give as 1 to 2.1. Four spas (3.60%) reported no physician involvement at all, and two did not know.

One finding concerns stock, not staffing. Of 93 spas that said they offered fillers, 64.52% said they carried hyaluronidase, 22.58% said they did not and 11.83% did not know. We report that as the paper does and draw no clinical conclusion from it.

The limits the authors state

It is one state. The authors say regional or national studies are needed.

The data are also only as good as whoever picked up the phone. Respondents ranged from front-desk receptionists to treating staff, the paper says, and knowledge varied. The website review could not show which staff deliver the weight-loss, hormone and IV services, and the authors say they "do not attempt to insinuate" that non-medically trained staff do.

A research grant from the American Society for Dermatologic Surgery, a physician society, supported the work, and the paper cites the position of the American Society for Dermatologic Surgery Association, which opposes "in-name-only" medical directors. The authors declare no significant interest with commercial supporters. Their conclusion is that consistent statewide regulation is needed. In our reading that is a view, since the study did not measure patient outcomes.

What it means for an owner

The study stops there. What follows is our analysis, not the authors'.

If Missouri is any guide, a spa that offers toxin, filler, microneedling and a laser has matched nearly everyone and distinguished itself from no one. Weight loss, on about half of websites in a list drawn up in 2023, was already crowded before FDA declared the semaglutide and tirzepatide shortages over and its grace periods for compounders ended in 2025. We covered that in our look at the GLP-1 line.

The 22.52% is the figure most likely to be quoted back at the industry. It sits below the 38.1% of 63 spas where a Las Vegas phone survey found an on-site physician supervising or performing procedures, though the two studies asked the question differently.

And the don't-know answers are cheap to fix. If two spas could not say whether a physician was affiliated, the gap may well have been at the front desk. Call your own number and ask.

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