One of the greatest threats to your family's financial security -- particularly now that the population is aging -- is unmanageable medical expenses.

Best to avoid this scenario by getting family members to eat properly -- lots of fresh vegetables, grains and fruit. Also, exercise is key.

It also helps to plan carefully.

Much as we advise you to check out financial advisers before taking the word of friends, Shawn D. Glisson, M.D., and Wynne A. Whitman, a tax and trust and estate attorney, suggest checking out your doctors before you become ill.

In their excellent new book, "Wants, Wishes and Wills" (Financial Times Press), the two advise that you check with your state medical board to make certain the doctor is licensed and has no formal disciplinary actions against him or her.

They also advise that you call to make certain he or she is on your health insurance plan.

Plus, double-check that the diagnostic facilities and hospitals your doctor uses are on your health insurance plan. Try to use those facilities -- even if you must travel farther. This can avoid the unnecessary cost and the disruption in your treatment by seeing a new doctor.

You can review accredited facilities at the Joint Commission on Accreditation of Healthcare Organizations Web site at www.jointcommission.org. Other sites to check: HealthGrades, at www.healthgrades.com, which rates hospitals; and Medicare at www.medicare.gov, which can help you search nearby hospitals.

Is a family member hospitalized? Know and justify the role of each new person entering the room. Ask questions. You don't want to pay for services you don't need.

Need a surgical procedure? Get a second opinion.

Don't neglect your health care proxy, which gives someone authority to make medical decisions on your behalf; a living will, which gives end-of-life directives; and a durable power of attorney to manage your financial affairs if you become incapacitated.

The two experts caution against limiting durable powers of attorneys. "We believe the general power of attorney is best, provided that you have a trusted individual to act as your agent," they say. Otherwise, your agent could be forced to spend time, money and energy proving to banks and brokerages that you're no longer able to act or that you have the right to conduct more business than it allows. Of course, double-check this issue with your own attorney.

What should you do with an old health care proxy and living will?

Be sure a statement is included in the new document revoking all prior instruments. Destroy the old documents in a shredder. Or write, "revoked," on the document in clear handwriting on the first page. If copies of the old documents have been given to other people, ask the individuals to destroy the documents.

Have an older family member who is terminally ill, but his or her health insurance won't cover some treatments?

The authors suggest that you may be able to cash out the person's life insurance policy.

If the illness is terminal and a doctor confirms that you have less than six months to live, you might be eligible for a life insurance policy's "Living Needs Benefit." This may let you tap the face value of your life insurance policy while living.

If the illness is not terminal, check into the prospect of a "life settlement." A settlement company may be able to buy a life insurance policy for about 10 to 35 percent of the face value. So if you have $100,000 policy, you could get up to $35,000 to pay medical bills.