While you're out scouring the after-Christmas sales this week, ask yourself whether you need a new pair of eyeglasses or an extra month's supply of aspirin.

The end of the year marks a deadline for many people to use money stashed away in flexible savings accounts. These handy vehicles allow workers to set aside a little money, before taxes, to cover any uninsured health expenses. Everything from prescription fees to contact lens solution may count.

They're a great benefit for anyone with some medical expenses, essentially allowing a tax break for health costs. Here's the wrinkle. For most people, any money left in those accounts at the end of the year may be lost forever, under the aptly named "use it or lose it rule." Or it may not.

To further confuse the situation, your employer may give you a little bit of a grace period. The Internal Revenue Service recently said expenses incurred through the following March 15 may be reimbursed with money saved in flexible spending accounts, if the plan makes such an allowance.

But not all plans do make such allowances. Make sure you check the details of your plan with your employer before deciding you have an extra two and a half months to stock up on cold and allergy medicine.

If your deadline arrives at the end of this week, you'll have to do some quick and creative shopping. In years past, I've stocked up on contact solution to exhaust my flexible spending account. Last year, I purchased enough first-aid supplies to make our house a neighborhood Red Cross station.

Review your plan's allowed purchases before running out to the drugstore. Odds are you'll also see some reminders when you go out shopping. Some retail outlets have started using flexible spending deadlines to run marketing campaigns, hoping to lure in some extra business at the end of the year.

1-800 CONTACTS (NASDAQ:CTAC) has a reminder about flexible spending accounts on the front page of its website, linking to more information about how to have your contact lens purchase reimbursed. Drugstore.com (NASDAQ:DSCM) has a special FSA store on its website, which also allows regular customers to view and print receipts from previous purchases eligible for reimbursement. Walgreens (NYSE:WAG) has a handy list that links to commonly eligible purchases.

If your deadline does arrive at the end of the year, you may want to consider a bulk purchase of any prescription drug you regularly take, if your insurance plan allows it. Otherwise, you'll have to come up with some quick purchases.

Try to buy things you know you'll use during the upcoming year. Over-the-counter medication purchases can be reimbursed in most cases. To get you started, think about cold, allergy, and sinus medication; pain relievers; antacids; anti-itch creams; and pretty much anything else in those aisles meant to take away your little aches and pains. Basic first-aid supplies, from alcohol swabs to thermometers, are also typically covered. Of course, there's always contact solution.

If you have a lot of money left in your account but only a few days to spend it, consider new eyeglasses, or new lenses for your old frames. Think about prescription sunglasses if you don't need new eyeglasses.

If you have a few more months to spend the money in your account, call your doctor or dentist right now and get an appointment to have that overdue cleaning or physical done. A visit to your acupuncturist or chiropractor may also be covered.

Then, remember to file your claim and get your reimbursement. You may need to take one or two of those aspirin before tackling the paperwork.

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Fool contributor Mary Dalrymple does not own stock in any company mentioned in this article, and she welcomes your feedback. The Fool's disclosure policy goes to the dentist every six months, right on schedule.