When uBiome was founded in 2012, the world was a different place. Silicon Valley was regarded with more reverence than suspicion, and DNA testing company 23andMe had just dropped its $299 price tag down to $99 to attract less wealthy customers interested in learning more about their genetics. UBiome promised people the same kind of insight into their bodies, but through their poop. Plus, it was for a good cause: uBiome billed itself as a citizen science project, where all samples would go toward gut microbiome research. “By joining uBiome, you can explore your own microbiome as well as take part in the process of scientific discovery,” the company’s website said.

Personal microbiome explorers were initially uBiome’s target audience, but as investors poured money into the company, its business model evolved. In a deep dive into the company’s unraveling, Business Insider reports that according to internal emails, uBiome “switched gears” in 2016 to marketing its tests as medical tools. Realizing that it had overpromised investors the number of billable tests run, the company approached previous customers and asked them if they wanted to “upgrade” to a medical-grade test called SmartGut. The upgrade was free for customers, but billed insurance companies thousands of dollars. Fast forward three years: After an FBI raid in April, the company has now ceased processing medical tests and is under investigation for financial misconduct.

The company’s claims that its tests could be medically diagnostic were always somewhat dubious. The gut microbiome is a constantly changing environment, and a single sample can’t tell you about its overall health. One former uBiome employee who had used the company’s tests told Business Insider’s Erin Brodwin that some of the results “remind me of astrology.” He went on: “You get one SmartGut report and you might say, ‘Oh, well that totally explains why I’ve been having such-and-such problem.’ Then you do it the next day, and you get completely different results.”

Science and astrology are often seen as opposite poles, and this former employee’s words seem carefully chosen to draw on that contrast. The implication is that anything making a scientific claim, like a medical test, should not be as squishy as astrology. Yet the same thing that drives some people toward astrology drives others toward mail-in test kits: People want to learn more about themselves and make sense of why they are the way they are. Your life might be fine, but perhaps it could be better if you understand yourself on a deeper level.

After all, that’s where 23andMe started. There was novelty in a test that told you where your ancestors came from, and the company’s website in 2008 reflects that, using words like discovery, fun, and empowerment. The company still offers many tests that seem born of idle curiosity more than anything else, like what genes you have for metabolizing coffee. This type of result invites armchair self-diagnosis: Ah, so maybe my genes explain why I can’t handle more than a cup of coffee without getting super jittery! In a review of the 23andMe user experience, Sofia Sokolove writes in Alcalde that her report turns up a high caffeine metabolism, which “feels like a solid piece of information to wield over friends that judge me for a 5 p.m. coffee. And I brag to everyone who will listen about my muscle composition, which apparently is, ahem, ‘common in elite athletes.’ ” She’s eager to know more about her genetic traits: “There’s just something inherently compelling about learning why I am the way that I am.”

One might turn to astrology for the same type of meaning-making. You have about as much control over the cosmos as you do your genetics, but perhaps returning to core elements of your identity can reveal new insights. A horoscope might not be based in science, but if you take the time to read it and believe it’s speaking to you, it might spur you on to examine why a friendship feels off or why you’re feeling uninspired at work. It’s not a coincidence that astrology, too, is having a cultural moment: Horoscope app Co-Star just raised $5 million to expand from iOS to Android, and astrology social media accounts like Astro Poets have amassed hundreds of thousands of followers. In the Atlantic, Julie Beck explores why millennials are so into astrology right now:

It does give one a pleasing orderly sort of feeling, not unlike alphabetizing a library, to take life’s random events and emotions and slot them into helpfully labeled shelves. This guy isn’t texting me back because Mercury retrograde probably kept him from getting the message. I take such a long time to make decisions because my Mars is in Taurus. My boss will finally recognize all my hard work when Jupiter enters my tenth house. A combination of stress and uncertainty about the future is an ailment for which astrology can seem like the perfect balm.

But the majority of Americans don’t believe astrology is scientific; many of the people Beck interviews see it as a tool for contemplation, not an empirically rigorous practice. Mail-order test companies, however, give off that air of scientific authority. People might be more apt to believe that a test using your spit, blood, or poop will yield scientifically rigorous information about your health and physiology.

Take, for instance, the claim that a genetic analysis can help suggest diets and exercises tailored for your body. On its face, this seems plausible, but there isn’t yet strong evidence linking genetics and any kind of personalized health plan. Certainly, it can’t hurt to know what genes you have, but will knowing actually yield actionable results? When the Verge’s Angela Chen tried one such test, she concluded that it was “unlikely to do major harm, but it’s unlikely to help either.” She, too, found a parallel between her results and astrology, calling our DNA “the original birth charts.” A range of customers have also reported being unimpressed with their mail-in test results.

Disappointment is one thing, but the darker side of these tests is when a company overpromises their tests’ diagnostic abilities, providing an avenue for people to seek astrology-style answers to questions that really should be addressed by live medical experts. A single, easy-to-take test may seem authoritative, but there could be important missing context that a trained professional could provide, or they may suggest a different diagnostic tool entirely. In the case of uBiome, gastroenterologists say the company’s diagnostic test can’t hurt, but is unlikely to capture the full complexity of the gut. That would require longer-term monitoring and multiple tests over time.

But just taking a test can lead people to mistakenly believe they know more about their health than they actually do. For instance, food sensitivity tests, like one offered by health test company EverlyWell, use a customer’s tiny pinprick of a blood sample to determine their immune responses to dozens of foods.* The test measures the blood’s reactivity to an immune protein called Immunoglobulin G; high IgG levels are interpreted as a show of food sensitivity. But medical experts say IgG tests are not a reliable way of measuring allergies or sensitivities, even if some people report feeling better after cutting out certain foods at the recommendation of their IgG tests. Rather, one doctor told NPR, this “huxterist testing is keying off of the placebo effect”: You might feel better just because you took a step toward understanding what’s “wrong” with you. But in the long run, writes one nutritionist, at-home food sensitivity tests are “a confusing distraction … in the pursuit of actually helpful and actionable answers.”

These tests let people seek astrology-style answers to questions that really should be addressed by live medical experts.

Tests can also be used to “confirm” existing beliefs about health and wellness. One recent example of this is how some people are using 23andMe tests to seek medical exemptions for vaccinating their children. They use the test to analyze their children’s MTHFR gene, a move that’s based on an overinterpretation of a 2008 paper that found people with certain genetic mutations are at greater risk of developing adverse reaction to smallpox vaccines. That this finding is being used to justify medical exemptions on the basis of linking vaccines with autism is an outcome the paper’s authors did not expect, and that one author of the paper called “illogical and inappropriate.”

That’s not to mention the risk that these tests are sometimes just straight-up wrong, or the serious privacy concerns with sending companies your biological data. But if there’s one thing we can learn from uBiome’s failure, it’s that when companies rebrand services once marketed as “genetic explorations for the curious” as diagnostic tools, consumers should be wary of their claims.

Personalized genetic readings can still be fun, even if they don’t promise the sun, moon, and stars; genomics company Helix sells, alongside some dubious-sounding tests, personalized DNA clothing, tote bags, couch throws, and artwork. But if you’re really concerned about your fertility, your gut health, or your cancer risk? If you wouldn’t consult your horoscope, you might not want to consult a mail-in test either.

Correction, June 18, 2019: This article originally misidentified EverlyWell as a DNA test company. Though it offers DNA products, it also has health tests that don’t involve DNA.

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.