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Healthcare providers have become more and more interested in addressing the problem of high risk patients returning to hospital.

Patients who have had heart surgery or who suffer from hypertension are very expensive to care for, and much of the expense stems from the patients’ failure to take their medications and follow doctors’ orders at home.

Redwood City, Calif.-based Proteus Digital Health makes a system that reports to caregivers whether or not a patient has taken their meds, as well as a number of other biometric stats.

The system uses a tiny ingestible sensor that patients swallow with their medication every day. The sensor contains tiny amounts of magnesium and copper that react together and send a signal to a battery-operated patch that’s worn on the patient’s abdomen. The patch, which lasts about a week, reports its data to a tablet or smartphone via Bluetooth, and the device forwards the information up to the cloud. Once the data is in the cloud, it can be monitored by doctors and other caregivers.

Proteus became a company in 2001 and has been working with the FDA to approve its technology since the mid-2000s. The company has received a CE mark in Europe and FDA market clearance in the U.S. for its wearables and Ingestible Sensors.

A handful of health systems in the U.S. and U.K. are now testing the Proteus system in what Proteus calls a “private beta.” The company isn’t saying when the product will become generally available.

To fuel the rest of the beta testing, the company has taken an new $52 million to add to the $120 million it announced in early June. The total $172 million round, which Proteus says comes from a group of “new major institutional investors based in the United States, Europe, and Asia,” is certainly among the largest venture fundings of a digital health startup this year.

Proteus lists Carlyle, Essex Woodlands, Kaiser Permanente, Medtronic, Novartis, Otsuka, Oracle, and ON Semiconductor as existing investors.

“Investor confidence in Proteus is driven by customer excitement, our superior board and leadership team, and a unique technology platform that enables us to link one of the most valuable industries of the 20th century – pharmaceuticals – to the most important utility of the 21st: the mobile Internet,” said Proteus CEO Andrew Thompson in a statement Tuesday.

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