Primary care group One Medical is in talks to raise more than $200 million in growth capital from the private equity firm Carlyle Group, according to people with knowledge of the talks. The firm also aims to buy an additional $100 million worth of shares from existing investors.

The company is in the late stages of conversation, the sources say, as the deal is not yet done. The company declined to comment.

One Medical is a primary care group with offices in San Francisco, New York, Seattle and other cities across the country. It accepts insurance from most carriers, and and also lets users without insurance pay out-of-pocket. The company sets itself apart with its technology. In addition to online scheduling, the company offers a virtual medical team, a suite of mobile apps and has built its own electronic medical system rather than relying on a third party vendor.

One Medical in July of 2017 named former UnitedHealth group executive Amir Rubin as its CEO to replace its founder Tom Lee. At that time, Rubin told CNBC that the company had seen "tremendous growth" in its business that sells its primary care clinics into the employer market, and not just with consumers. One Medical in recent years has positioned itself as an on-site or nearby clinic to companies with large campuses, so that employees can access concierge medical care without leaving the office.

The company has raised more than $180 million in capital since it launched in 2007 from investors such as JPMorgan, Alphabet's GV, Benchmark and Maverick. One Medical's most recently reported valuation was more than $1 billion. It's not known where the current round values the company.