Beginning Dec. 18, CareFirst BlueCross BlueShield insurance will no longer be in-network for One Medical. (PicturePartners/Getty Images/iStockphoto)

A popular District primary-care group said it will drop the city’s largest health-insurance provider, leaving thousands of angry patients to choose whether to find a new doctor or a new insurer.

One Medical — a concierge-style practice that, for an annual fee, promises a more-efficient, less-stressful doctor’s visit — sent a brief email this past week to patients informing them that, beginning Dec. 18, their CareFirst BlueCross BlueShield insurance would no longer be in-network, a change that would mean more out-of-pocket payments.

CareFirst, which did not respond to a request for comment, released a statement placing the onus on One Medical for “seeking dramatic — egregious — increases in rates from CareFirst as well as additional mandatory charges from CareFirst members that would result in millions of dollars in additional costs to members. Such cost increases at a time when many are already struggling to pay for their healthcare are unconscionable.”

One Medical chief executive Amir Rubin agreed to an interview about the situation and then decided “for corporate integrity and various legal reasons we’re not going to engage in a public interview about ongoing contract negotiations,” said Vanessa Schenider, the practice’s vice president of marketing.

Instead, the company provided a statement pointing to a rise in health-care costs and premiums that it said drove the need to raise rates: “These dynamics — which can disproportionately affect independent practices such as ours — disrupt our ability to focus on clinical excellence and a great patient experience.”

One Medical, which began as a start-up in San Francisco in 2011, has five locations in Washington, with a sixth scheduled to open soon. It declined to say how many patients it serves.

The practice promises to improve visits by eliminating long wait times in offices, offering same-day appointments and allowing online referrals and prescriptions.

The notice of the coming change created enough of a firestorm on social media that @onemedical was trending on Twitter for a time Thursday. And with few details offered for the shift, upset patients were split over whom to blame.

“I don’t think I’m overstating the fact that @CareFirst should give in to whatever @onemedical wants #FIXIT,” read one tweet; another: “onemedical the world is already terrible! why did you make it worse!”

Robin Summer started a Change.org petition, which collected more than 1,000 signatures in a day. It included a letter sent to the CEOs of CareFirst and One Medical.

“Regardless of what led to the breakdown in the relationship between CareFirst and One Medical or who is to blame, the end of One Medical’s inclusion as an in-network provider through CareFirst will be a significant problem for many in the DC area,” the letter read.

Summer, 41, said that it was her first time launching a petition drive but she felt compelled to act when social media flared over the change and “it seemed like everybody in D.C. went a little nuts for a minute.”

An aim, she said, is “trying to show there is going to be a cost here to both of your sides so fix it.”

Several signers credited One Medical for having the best LGBT care in the District, something it advertises on its website.

While most patients pay a $200 annual membership fee for the convenience of same-day attention, for the past few years it has been waived for CareFirst members.

Mindy Moretti, 46, who is self-employed and gets her insurance through the federal exchange, initially paid the fee when she joined One Medical in 2013. She said it was worth it to be able to avoid the common hassles and frustrations of finding a good doctor with a competent and caring office that did not have long wait times for appointments.

“So when you find a situation that is great, they’re convenient, they take my insurance, they work together . . . no one wants to choose between their health insurance and their doctors,” Moretti said.

That’s the situation many CareFirst members find themselves in now. For those who do not get insurance through work and shop on the marketplace, like Moretti, do they switch to another carrier so they can continue using One Medical? Or do they stick with CareFirst and find a new doctor?

A third option is to continue with both and pay out-of-network costs to keep their doctors, which would be $175 for the first visit and $125 for every visit after that.

Deborah Chollet, a senior fellow at Mathematica Policy Research who has expertise in health insurance, said that it is impossible to know who is really to blame in this particular breakdown. CareFirst has already locked in its rate requests for 2018 based on how much it estimated paying out to providers, so if One Medical was asking for rates much higher than CareFirst anticipated paying, that may have led to their parting ways, she said.

CareFirst has operated with a nearly $1 billion surplus for a decade, which exceeds the appropriate reserve level by $268 million, and was ordered by D.C. insurance regulators to invest a portion back into the community — which it has not yet done, Chollet said. Financially, CareFirst could have enough money to absorb the additional One Medical costs by drawing from its reserves, she said, but noted that there would be little incentive for the company to do that.