As many common expenses spiral out of control, it's ever more critical to save money wherever possible. But socking away money, whether for short-term savings or long-term retirement, seems harder than ever now; gas tops $3 per gallon, milk prices have risen 40% in the past year, and wheat costs 60% more than last year. But there's one area where you can lower your expenses: prescription drugs.

Businesses like CVS Caremark (NYSE:CVS), Walgreen (NYSE:WAG), Rite Aid (NYSE:RAD), and even Wal-Mart (NYSE:WMT) like having customers come in to pick up their prescriptions, because they hope to lure those shoppers into extra in-store purchases. But a little comparison-shopping might give you a better deal for prescriptions by mail. (Your friendly local pharmacy might have a mail-order business, too.)

According to a study by the Lewin Group, mail-order pharmacies, such as Medco (NYSE:MHS) and Express Scripts (NASDAQ:ESRX), can save you as much as 10% overall, compared with the price of medications at conventional pharmacies. They tend to be especially good at getting you generic versions of drugs as soon as possible, offering extra savings. (That's at least partly because such pharmacies enjoy a fatter profit margin on generics, aligning their best interests with your own.)

Seeking out the lowest prices for prescription drugs is a worthwhile habit. As we get older, we'll likely spend increasing amounts in this category. According to a survey commissioned by Medco, about one-quarter of retirees spend 10% or more of their income on medications. Remember, that's just the drugs, not other medical services.

Check with your health plan to see what options you have, pharmacy-wise. Save as much as you can, and beef up your savings and investment accounts. You can get other money-saving ideas in these articles:

Longtime Fool contributor Selena Maranjian owns shares of Wal-Mart. Wal-Mart is a Motley Fool Inside Value recommendation. Try any of our investing services free for 30 days. The Motley Fool is Fools writing for Fools.