Raleigh, N.C. — The University of North Carolina system requires all students to have health insurance coverage, but the cost of a plan the system offers has more than doubled in two years.

The insurance requirement started in 2010, and about one-third of students on the system's 16 university campuses buy their policy through UNC's provider, New York-based insurer Chartis. The rest of the students have other coverage, usually through their parents.

The average cost of the Chartis policy started at $695 a year, but it rose to $847 last year. Tuition bills that are now arriving in student mailboxes for the 2012-13 school year include a $1,418 health insurance premium.

"That's a lot of money to come out of our pocket. I hated to see that," said Kerwin Chavis, a senior at North Carolina State University. "That's why I'm here at work. I'm actually trying to get up some money so I can pay for it this year."

Bruce Mallette, the UNC system's vice president for academic and student affairs, blamed the increase on a high number of claims by students on the policy.

"It was a very affordable plan," Mallette said. "If you look nationally, the pricing we had in the first two years was very, very competitive, and students utilized it and utilized it and utilized it."

Chartis initially underestimated the cost of the claims, he said, and UNC's contract doesn't limit yearly increases.

"(The company) had a review of all the data to justify any increase that was there, so there was no cap," he said.

Chartis officials declined to comment.

UNC plans to re-bid the insurance contract next year, Mallette said.

In the meantime, he said, the university health plan is still a good deal, noting that the University of South Carolina charges its students $1,624 a year for health coverage and the University of Virginia charges $2,400.

Students also are free to shop around for cheaper health coverage elsewhere, he said.

"If they prefer to get a different set of benefits at a different cost premium, they can shop with any vendor and seek a combination that best fits their needs," he said.

Chavis didn't shop around this semester, but he said he might for the spring semester.

"It's getting larger and larger," he said of the premium. "(I'm) trying to get out of here as quick as I can."

Students who opt out of the Chartis plan must prove they have other health coverage by Sept. 15 to avoid being charged.