COLUMBIA — A dozen insurers will no longer write health policies in South Carolina, impacting more than 30,000 people, according to the state Insurance Department.

Agency spokeswoman Ann Roberson said insurers cited the federal health care overhaul in abandoning the state’s individual or small group market. State law requires companies to notify the agency only if they’re discontinuing policies in an entire market segment.

Director Ray Farmer said those notices helped him estimate that more than 150,000 South Carolinians overall are being forced from their policies.

Last week, his agency issued guidelines for insurers wanting to extend coverage to clients who previously received termination notices.

Millions of policyholders nationwide have received such notices, despite President Barack Obama’s repeated promise that those who like their health plans would be able to keep it under the 2010 overhaul. People learned that, to keep coverage, they needed to switch to a more comprehensive, and often more expensive, policy that complies with the federal law.

The backlash over canceled plans, including from his own party, caused Obama to take administrative action to let insurers continue for a year policies that the law considered substandard.

Farmer said last week that departing companies don’t have that option, since state law bars them from writing policies in the abandoned segment for five years. But Roberson said Monday they too are invited to participate.

The agency has given insurers until Dec. 2 to decide. On Monday, the agency provided insurers with a standardized letter for informing policyholders of their new options.