Should I Join a Medicare Part D Prescription Drug Plan if I Have Other Drug Coverage?

Usually not, for two reasons: First, if your other drug plan covers all the prescription drugs you regularly take, enrolling in a Medicare Part D prescription drug plan would be a waste of money -- one plan or the other can pay for a single prescription, but not both. The second reason is that if you ever lose or drop the other coverage, you can then join a Medicare Part D prescription drug plan without penalty.

This ability to enroll later without penalty in a Medicare Part D plan doesn't apply to all drug coverage. You are protected from the Medicare Part D late enrollment penalty only if the other health insurance qualifies under Medicare Part D rules as "creditable prescription drug coverage." This insurance includes:

• Employer-sponsored health insurance with prescription drug benefits. This can include insurance you receive as a current worker, the spouse of a current worker, a retired worker, or the spouse of a retired worker. If you have a question about whether your employer-sponsored insurance qualifies as creditable drug coverage under Medicare Part D's definition, ask at the benefits office of the employer that provides the insurance.

• A Medicare Part C Medicare Advantage plan with comprehensive prescription drug benefits. If your Medicare Part C Medicare Advantage plan includes prescription drug benefits, you don't also need a Medicare Part D drug plan.

• V.A. medical benefits. Not all veterans and dependents who get some medical care from the V.A. get prescription drug coverage. If you receive any V.A. medical benefits that include some drug coverage, check with the V.A. facility where you receive care to find out if your drug coverage is "creditable" under Medicare rules.

• TRICARE or the Federal Employee Health Benefits (FEHB) program. These federal employee health insurance programs include creditable drug coverage.

If you have some drug coverage but it doesn't qualify as "creditable," Medicare will impose a penalty on you -- when you do eventually join a Medicare Part D prescription drug plan -- if you don't enroll in a Part D plan when you're first eligible for it. The penalty is a 1 percent rise in your premiums, on any Part D plan you join, for every month you delay after first becoming eligible.