By the time your children toss their high school graduation caps into the air, they'll probably have chosen a college and mapped out their freshman courses. But is their health insurance securely in place?

Often, the medical plan a parent has through work will cover children up until they're between 20 and 24 years old, whether they live at home or away at school. However, because college health plans at some schools are subsidized by tuition (though not necessarily subsidized for the student's spouse or dependents), college plans might save parents money. If you don't have any health insurance for the student, college health plans could be a good solution.

College plans are not free, and the benefits vary from college to college. Committees from each college meet with insurance companies and design plans specific to their schools.

College plans sometimes limit preventive care, but students often can go to the college health center for free services. Many times there's no charge for office visits to the health center, although students may be charged for lab work, physical therapy, X-rays, prescriptions, and procedures such as treatment for a wound. Other covered services may include mental health, well-child care, newborn and infant care, routine pap and pelvic exams, cholesterol screening, and routine STD/AIDS testing. Mammograms are usually covered when prescribed by a doctor.

Typically, college health plans will pay 100 percent of charges for covered services at the college health center. For coverage outside the health center, including out-of-state providers, a student's coverage may drop to 70 percent and impose a deductible.

In addition, state laws and market factors play significant roles in the policies offered to students. As a result, there's a wide range of premiums and benefits that vary from college to college.

Pre-existing conditions can create problems

Your state may allow "blanket disability" products to exclude coverage for pre-existing conditions even if the state won't allow the exclusion on "group disability" products. This means insurance companies can refuse to provide benefits for the treatment of medical conditions that existed before the coverage took effect. So before you sign up for a college health plan, make sure you know whether the plan is a blanket disability product that won't cover treatment for your asthma or any other pre-existing condition — and, if so, just how "pre-existing conditions" are defined in the plan.

People sometimes buy a college's health insurance even when the student is covered under a parent's plan if the policy requires doctor referrals for care. Obtaining referrals across states can be problematic. (Many HMOs require referrals for visits to out-of-network providers.) Parents who want their out-of-state college children to get prompt care without calling home for a physician's referral might want to consider college health plans.

Cost and the problem of referrals shouldn't prevent the student from having health insurance, whether it's their parent's plan or the school's plan. A serious illness or injury could have long-lasting negative financial consequences for the student, the parent, or both.