More than a million California small-business owners and individual policyholders face a wave of health insurance premium increases in the coming months that range from single digits to as high as 20 percent.

Starting Sunday, about 101,000 Anthem Blue Cross small-group customers will see their premiums go up an average of 13.8 percent but as high as 20.5 percent. At the same time, more than 16,000 small businesses covered by Aetna will receive hikes averaging 3.7 percent. While a few will see decreases, others will get hit with increases of more than 20 percent.

Some of these increases may not reach the nosebleed levels they have in recent years when many consumers faced raised rates of nearly 40 percent and a few experienced hikes higher than 75 percent. But for those who have experienced increases year after year, this latest round is still tough to manage.

Health insurance has been in the spotlight this week with the U.S. Supreme Court weighing the constitutionality of the federal health law. A key issue is whether Americans should be required to buy health insurance, so affordability is an issue.

"We're in the middle of a week where the Supreme Court is considering the mandate and whether insurance would be affordable without it," said Carmen Balber with Consumer Watchdog, a California group spearheading a campaign to put a measure on the ballot to regulate health rates. "The only way we're going to ensure affordability is requiring oversight of these massive rate increases."

Anthem Blue Cross customer Alison Heath, 56, of San Francisco will get hit with a 19.7 percent increase effective May 1 – her third increase since October 2010, making for a total increase of 66 percent.

"There's a breaking point somewhere," she said. "I keep feeling like we're awfully close to it."

Her insurer Anthem, which is owned by WellPoint Inc., had previously proposed to raise rates averaging 10.4 percent but as high as 30 percent for some 600,000 consumers. It agreed earlier this month to lower rate hikes to an average of 8.2 percent, but some, like Heath, will experience higher increases.

Anthem officials said they agreed to modify the rates even though a third-party review found the rates in line with the federal health legislation. "In modifying our rate filings we were sensitive to the challenges increasing health care cost places on our individual members," said Anthem spokesman Darrel Ng.

Other increases are planned for May 1, affecting small-group customers of Health Net and UnitedHealthcare.

"These rates have been calculated to cover the continued steep increases in the cost of medical care," said Health Net spokesman Brad Kieffer.

Even those consumers who are not facing premium increases say they have been slammed by increased deductibles, higher co-payments and reductions in benefits.

Christopher and Janet Hildreth, owners of Tree Lovers Floors in San Francisco, didn't get a premium increase for the first time in many years, but said Blue Shield of California eliminated their policy and replaced it with one that has less coverage and more costs. For example, it no longer covers one of
Christopher's brand-name asthma medications, so he now has to pay more than $200 out of pocket for the drug.

"There is an increase; it's just hidden," Janet Hildreth said. "It's not an increase in reality."

Victoria Colliver is a San Francisco Chronicle staff writer. [email protected]