Trenton, N.J. ? Consumers in at least four states who buy their own health insurance are getting hit with premium increases of 15 percent or more — and people in other states could see the same thing.

Anthem Blue Cross, a subsidiary of WellPoint Inc., has been under fire for a week from regulators and politicians for notifying some of its 800,000 individual policyholders in California that it plans to raise rates by up to 39 percent March 1.

The Anthem Blue Cross plan in Maine is asking for increases of about 23 percent this year for some individual policyholders. Last year, they raised rates up to 32 percent.

Kansas had one recent case where one insurer wanting to raise most individual rates 20 percent to 30 percent was persuaded by state insurance officials to reduce the increases to 10 percent to 20 percent. The insurance department would not identify the company but said it was not Anthem.

And in Oregon, multiple insurers were granted rate hikes of 15 percent or more this year after increases of around 25 percent last year for customers who purchase individual health insurance, rather than getting it through their employer.

Premiums are far more volatile for individual policies than for those bought by employers and other large groups, which have bargaining clout and a sizable pool of people among which to spread risk. As more people have lost jobs, many who are healthy have decided to go without health insurance or get a bare-bones, high-deductible policy, reducing the amount of premiums insurers receive.

Steep rate hikes in this sliver of the insurance market — about 13 million Americans, as of 2008 — have popped up sporadically for years. Experts see them becoming increasingly common.

“You’re going to see rate increases of 20, 25, 30 percent” for individual health policies in the near term, Sandy Praeger, chairwoman of the health insurance and managed care committee for the National Association of Insurance Commissioners, predicted Friday.

Most states don’t have the legal authority to block or reduce health insurance rate increases, noted Praeger, who is also the Kansas insurance commissioner.

“When you see stories like (Anthem’s), you can almost guarantee there’s going to be increased consumer protection activity” in state legislatures, she said.

Her group doesn’t track rates state by state, but Praeger said it likely will start doing so, “if we don’t get any kind of meaningful reform at the federal level.”

Politicians and even some health insurers, including Anthem, are urging a revival of the stalled effort in Congress to overhaul the health care system, arguing everyone needs to be covered by health insurance in order to prevent such premium spikes.