Tens of thousands of Iowans who buy their own health insurance are about to receive a shock in the mail.

Wellmark Blue Cross & Blue Shield is sending letters this week telling about 30,000 customers it plans to raise their premiums by 38 percent to 43 percent next year.

Wellmark sells about three-quarters of individual policies in Iowa’s health-insurance market. The steep increases will affect people who bought relatively new plans that comply with rules of the Affordable Care Act.

Another 90,000 Wellmark customers who hold older individual insurance plans are expected to face smaller increases, which will be announced in June. The increases being proposed this week also don’t affect the hundreds of thousands of Wellmark customers who obtain coverage via their employers. Their premiums are expected to rise less, because they are in larger, more stable pools of customers.

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