UnitedHealth Group Inc. is buying Change Healthcare, a health technology firm based in Nashville, in a $13 billion deal that is among the largest by the Minnetonka-based company.

UnitedHealth said Wednesday it will fold the company into Optum, its health information and technology business. It is the second-largest acquisition in company history, further widening UnitedHealth's empire beyond its legacy health care plans.

While UnitedHealth is best known as the nation's largest health insurer, it is seeing significant growth in its medical services that fall under Optum — which is expected to account for about 50% of UnitedHealth's overall earnings in 2021.

Change, with about $3 billion in annual revenue, will deepen UnitedHealth's already sizable presence in health services, with products ranging from revenue management to customer experience platforms to medical imaging data.

Change will be combined with OptumInsight, which offers software, data analytics and related services to health care providers. It is the smallest division in Optum and had about $11 billion in revenue last year.

Neil de Crescenzo, Change's chief executive, will assume the top position of the newly expanded OptumInsight.

UnitedHealth will pay $25.75 a share for Change, about a 40% premium to Change's closing share price on Tuesday and a price that puts Change's value at nearly $8 billion. UnitedHealth will also assume about $5 billion of debt owed by Change.

On a cash basis, the only larger deal by UnitedHealth was its $13.2 billion purchase of Catamaran Corp., which boosted its presence in the business of prescription-drug benefit management.

Shares in UnitedHealth rose 4.2%, the sixth-biggest gain of the 30 stocks in the Dow Jones industrials as the benchmark index hit a new record Wednesday. Change shares rose about 30% to $23.72, still below the price UnitedHealth offered for them.

"We believe [Change] fits very nicely within OptumInsight," Steven Halper, a healthcare IT analyst at Cantor Fitzgerald, wrote in a note to investors. "Change will add key technologies to optimize health care delivery and workflow while minimizing wasted costs."

UnitedHealth Group is Minnesota's largest company by revenue, bringing in an estimated $256.5 billion in 2020. The company, at its annual investor day last month, projected overall revenue to grow between 8 and 9% this year.

It employs about 325,000 people, including about 18,000 in Minnesota.

UnitedHealth executives declined a request for an interview. A spokesperson did not say whether the operational base for OptumInsight will remain in the Twin Cities or move to Nashville.

"Together we will help streamline and inform the vital clinical, administrative and payment processes on which health care providers and payers depend to serve patients," Andrew Witty, president of UnitedHealth Group and chief executive of Optum, said.

Kristen Leigh Painter • 612-673-4767