(Bloomberg) -- DNA4Life offers a $249 test to help customersunderstand whether their genes put them at risk ofhaving bad reactions to more than 100 common medicines.

Read: Benefits idea: DNA testing

Interleukin Genetics sells a $169 test that “may help you losemore weight by properly matching diet and exercise plans” togenetic profiles.

Read: Lab Corp to let consumers order owntests

And DNA-CardioCheck has suggested its test, at $450, is a"reliable method to determine whether or not you might be atrisk for developing blood clots which might result incardiovascular disease."

All three companies got letters from the Food and DrugAdministration in early November suggesting they didn’t have theproper clearance to sell medical tests to consumers.

It’s the latest sign that regulators are concerned about howcompanies market DNA tests for health insights, sometimes bypassingdoctors entirely.

There’s good reason for that worry: For most people, the geneticanalysis available today doesn’t provide much meaningful healthinformation at all.

DNA tests can reliably establish family ties, like paternitytests, or reveal a person’s ethnic heritage.

They can also tell whether people are at risk for certain rarediseases like cystic fibrosis that are directly linked togenetic mutations, or for passing the risk on to theirchildren.

But when it comes to information relevant to people’s health,especially about common conditions like heart disease or diabetes,the value of genetics becomes much murkier.

"Right now, almost all of this is premature and not terriblyuseful to individuals,” said George Annas, a Boston Universitybioethics professor and co-author of Genomic Messages, a book abouthow genetics is changing medicine. “It’s complicated, and thesetesting companies are trying to make it appear that it’s much moresimplistic so they can sell you a product."

Companies see a gold mine in turning genetic data intoinformation people can use to stay healthy or battle illness.

A few years ago, Booz Allen Hamilton estimated that therewere nearly 3,000 tests available; market researcher Technavio saysthe industry is growing by close to 10 percent ayear.

Many of these tests are available only through health careproviders.

The FDA didn’t tell the three companies to stop selling theirtests.

But the agency pointed out that it considers them medicaldevices that need regulatory clearance, and asked forjustifications if they believed the clearance wasn’t necessary.

"The FDA actively regulates genetic tests sold directly toconsumers to make sure they are safe and do what they claim to do,"spokeswoman Jennifer Dooren said in an email. "Without FDAoversight, the safety and efficacy of the these tests have not beendetermined and could potentially lead to patient harm."

DNA4Life and DNA-CardioCheck didn’t respond to requests forcomment.

Mark Carbeau, chief executive of Interleukin Genetics, said thecompany’s main product, a test that predicts the risk of gumdisease, is sold primarily through dentists. Other products "can bepurchased by a consumer, though a medical professional needs to beinvolved,” Carbeau said. "We think, properly done, genetic testsoffer real value to the health care community, and we’re certainlysupportive of the FDA’s efforts to protect the public and provideguidance.”

The FDA has cracked down on testing companies marketing straightto the public before.

In late 2013, it ordered 23andMe to stop selling its personalgenome analysis.

This past February, the agency approved 23andMe’s test for alimited use, to detect whether people carried the gene for Bloomsyndrome, a rare genetic disorder.

The company has since added other approved uses to determinewhether people carry mutations that could be passed down tochildren.

One of the risks of making genetic tests available directly toconsumers is that people may confuse diseases caused bycomplex risk factors with those caused by a single geneticabnormality.

While a single gene mutation can cause cysticfibrosis, “for things like cardiovascular disease that’s justnot true," said Michael Christman, chief executive of the CoriellInstitute, a Camden, N.J., research center focused on geneticmedicine.

Unlike some rare hereditary conditions, many pieces of aperson’s DNA may influence his or her risk for heart disease,cancer, or diabetes, and they’re not all well understood.

And genetics are only one risk factor, along with environmentalexposures and lifestyle, that help determine whether someone willget a disease.

In an ideal world, genetic tests would go through physicians orother experts capable of interpreting results, Christman said.“People joke, there’s the $1,000 genome followed by the $1million interpretation,” he said. "The interpretation iscomplicated, and it needs to be done very well.

Christman said the greatest potential for genetic medicine rightnow is using DNA profiles to determine how people might react todifferent drugs or doses, a field called pharmacogenomics.

More than 100 drugs have information on their labels about howpeople with certain genetic markers may respond differently.

The challenge ahead for the FDA is policing the evolving marketfor genetic testing.

"They’re trying to figure out, 'How do we help consumers andproviders that don’t work in genetics all the time to distinguishwhat tests are useful and what aren’t?' " said Joy LarsenHaidle, president of the National Society of GeneticCounselors. "What got some of the labs into trouble beforewith the FDA was you could send a sample of saliva to a couple ofdifferent labs and you would get very different results to the samequestion."

Copyright 2018 Bloomberg. All rightsreserved. This material may not be published, broadcast, rewritten,or redistributed.