The US Food and Drug Administration has imposed a ban on a company offering personal genetic screening to the general public.
Google-backed 23andme has been ordered to "immediately discontinue" selling its saliva-collection tests after failing to provide information to back its marketing claims.
The tests aims to show how personal genetic codes may affect future health.
The company said it would address concerns.
The start-up has been operating since 2006 and was co-founded by Anne Wojcicki, the wife of Google co-founder Sergey Brin.
For $99 (£61), users receive a kit allowing them to take sample of saliva. This is sent to the company and in return users receive a readout of their genetic code.
The website promises reports on 254 health conditions and traits as well as offering to help people trace their genealogy.
Under FDA rules, the company must provide proof about how accurate its detection methods are as well as supplying the error rates from its personal genome service (PGS).
In a public letter the FDA said that 23andme had not supplied this information, despite increasing its marketing campaign and the scope of its tests.
"FDA is concerned about the public health consequences of inaccurate results from the PGS device - the main purpose of compliance with FDA's regulatory requirements is to ensure that the tests work," said Alberto Gutierrez, director of the FDA's centre for devices and radiological health, in a letter to the company.
"Patients relying on such tests may begin to self-manage their treatment through dose changes or even abandon certain therapies depending on the outcome of the assessment," he added.
Despite hundreds of emails and 14 face-to-face meetings with 23andme, little evidence had been provided, the agency added.
The company said: "We recognise that we have not met the FDA's expectations regarding timeline and communication regarding our submission.
"Our relationship with the FDA is extremely important to us and we are committed to fully engaging with them to address their concerns."
The Center for Genetics and Society said it welcomed the FDA's stance.
"Our society regulates medical products to protect public health. Without strong public oversight, we're back to the era of snake oil," said executive director Marcy Darnovsky.
"The public agency charged with protecting public health has finally lost patience with a private company that seems to think it doesn't have to play by the rules," she added.
It is not the first time the company has hit the headlines. A "build-a-baby" patent, which offered to show perspective parents what traits a future baby may have, was criticised by the Genetics and Society organisation.
The company described the system as an enjoyable way for parents to "dip their toes into genetics".
There are an increasing number of companies offering low-cost home genetic testing - but some medical experts have raised questions about the accuracy of the tests, and asked what benefit they offer to consumers.