Apple‘s costly legal battle with medical technology company Masimo has become even more expensive. A federal judge has ordered the iPhone maker to pay an additional $184 million in prejudgment interest on top of the $634 million patent infringement damages awarded to Masimo last year, pushing Apple’s total liability to roughly $818 million before any continuing post-judgment interest is added.

The latest ruling stems from Apple’s long-running dispute with Masimo over pulse oximetry technology used in the Apple Watch. In November 2025, a California jury found that Apple infringed Masimo patents related to low-power blood oxygen monitoring and awarded the medical technology company $634 million in damages. Apple has maintained that it disagrees with the verdict and is appealing the decision.

Why Apple owes more than the original verdict

The new $184 million award isn’t an additional penalty for infringement. Instead, it represents prejudgment interest—money intended to compensate Masimo for the time it went without royalty payments it would theoretically have received if Apple had licensed the patented technology.

Judge James Selna rejected Apple’s argument that awarding prejudgment interest would unfairly benefit Masimo. Citing guidance from the U.S. Supreme Court, the judge said that interest is meant to make the patent holder whole by accounting for the delay in receiving compensation.

Masimo had actually sought an even larger interest payment. The company asked the court to calculate interest at a 7% rate, which would have increased the award to approximately $243 million. Instead, the judge used Masimo’s own borrowing rate and applied annual compounding from the time the infringement began, resulting in the lower $184 million figure.

Separate from the Apple Watch import ban

Although both cases involve Apple Watch blood oxygen technology, this damages award is separate from the high-profile U.S. import dispute that forced Apple to disable the Blood Oxygen feature on certain Apple Watch models sold in the United States.

That earlier conflict was decided through the U.S. International Trade Commission (ITC), which found Apple had infringed different Masimo patents. To continue selling affected Apple Watch models in the U.S., Apple removed blood oxygen functionality from new domestic units while it continues challenging the ITC ruling through the courts.

What happens next?

Apple is expected to continue appealing both the underlying $634 million jury verdict and the latest interest award. Until the judgment is resolved and paid, additional post-judgment interest will continue to accrue, potentially increasing Apple’s final bill beyond the current estimated $818 million.

While Apple generates hundreds of billions of dollars in annual revenue, the case remains significant because it underscores the financial and legal risks surrounding health technology patents as smartwatches evolve into increasingly sophisticated medical devices.