Oura Says It Isn't a Medical Device. The Ad Compared It to a Sleep Lab.

Somebody at Oura approved a sentence putting a percentage next to the words clinical sleep lab. That sentence is what a federal court is now being asked to rule on. The algorithm behind it is barely in dispute.

The case is Surber v. Oura, filed this month in the Northern District of California by the Clarkson Law Firm on behalf of a California buyer of an Oura Ring 4. It challenges three pieces of marketing: "Built for accuracy," "Unparalleled Accuracy," and "95% Sleep Staging Accuracy compared to clinical sleep lab." Oura told MobiHealthNews it stands behind its science and will defend the allegations.

Call it a health wearable that oversold its AI and you have the easy reading. I don't buy it. The model is doing roughly what Oura says it does. What went wrong here was a product decision, and it went wrong long before any lawyer read the website.

Both sides describe the same ring

Set the complaint's technical argument beside Oura's response and they agree about the hardware. Sleep gets defined in the brain, the plaintiff argues, through electrical activity, eye movements and muscle tone, read by electrodes on the scalp and leads placed around the eyes. A ring on your finger reaches none of that. Oura doesn't say otherwise. Its own statement describes a device that estimates sleep stages from heart rate, movement, breathing and temperature, and calls itself neither a medical device nor a substitute for a clinical sleep study.

What they are fighting about is one number and the phrase bolted to it.

For its evidence the complaint leans on a 2025 study in Nature that put the ring's sleep-stage agreement near 53 percent across 45 nights. I'd want to read that paper before I treated the figure as settled. Forty-five nights is a small pile of data, and a number this convenient for the people suing deserves the same scrutiny as the claim it targets. Oura answers with more than 1,200 nights of collected data, which is a company number and gets read the same way. Neither figure has been tested by anyone except the party citing it.

Not a medical device answers a question nobody asked

Oura's own framing, that the ring was never a medical device, is also its defense, and that framing is the part worth sitting with. Plenty of founders are running the same play. Staying in general wellness is a real strategy. Keep off disease claims, keep the risk profile low, and the FDA has better things to do than review your app. Where founders get it wrong is treating that as the finish line. It's a boundary on one agency's attention, and that's all it is.

It decides which regulator reads your claims before you ship. Nothing about it touches whether those claims are actionable afterward. California consumer protection law, express and implied warranty, and fraud by misrepresentation are all pleaded in this complaint, and not one of them turns on how the FDA classified the device.

Then there's the comparator. "Compared to clinical sleep lab" reaches over and borrows the authority of polysomnography, the exact standard Oura says it should not be measured against. Declining the jurisdiction is allowed. Cite its gold standard in your advertising while you decline it, and you have volunteered for a different forum.

The expensive word, in a different room

That borrowed authority has a price. The same trade shows up in a room with no jury in it. In a 510(k), the most expensive word a founder can write is "better." Substantial equivalence means equivalent. Frame a technical difference as an improvement and you have made a superiority claim, which can push you out of the pathway the whole submission was built around. The disciplined version says the difference raises no new question of safety or effectiveness, so the device can be evaluated inside the same bounds.

A comparison claim changes what you are asserting, and it summons a reviewer nobody budgeted for. For Oura, that reviewer is a federal judge.

Oura's calendar makes that expensive. The company raised $900 million at a valuation around $11 billion, filed confidentially for an IPO in May, and says it is on pace to pass five million paid members. A company at that stage has an S-1 to write, and its accuracy claims are now part of what has to be disclosed.

Dave Saunders is the founder of Base Reality Group and a Fractional CPO for product companies. He was a founder and operator at Galen Robotics, where the surgical-robotics platform earned FDA De Novo authorization in 2023, and he managed a 35-patent portfolio licensed from Johns Hopkins. He wrote Founders Who Finish and publishes The Build. More about Dave →