Many years ago, I was getting tension headaches. Along with trying natural treatments, such as exercising and drinking more water, I bought a large bottle of ibuprofen for extra help whenever my head severely throbbed.

The largest bottle gave me the most bang for my buck, and since it contained so many pills, I figured that I wouldn’t have to buy any more for a long time. As it turns out, my thinking was foolish.

A year and a half after I bought the bottle, I took a pill from it and it wasn’t making me feel any better. At first, I wasn’t sure why. But then I realized that the bottle of pain reliever—though I hadn’t even used one-quarter of it—had expired.

I used to think that most expiration dates were mere ploys devised by drug companies to make us toss perfectly good medications and buy more.

I wanted to prevent my readers from making the same mistake I made, so I spoke with Amy Tiemeier, PharmD, assistant professor of pharmacy practice at the St. Louis College of Pharmacy in Missouri, who explained that expiration dates do, in fact, serve a real purpose, including to help ensure the chemical stability of the drug.

WHAT EXPIRATION DATES REALLY MEAN

Until a medication’s expiration date, the manufacturer guarantees that the drug will be chemically stable, so it’s essentially guaranteeing its full potency and safety…but after that date, it can’t, said Dr. Tiemeier. In other words, the drug might work perfectly well after that date or it might be less effective or totally ineffective—you just won’t know for sure. And on rare occasions, taking a pill past the expiration date can hurt you, she added. Very few drugs become toxic, she continued, but antibiotics in the tetracycline family (including tetracycline, doxycycline and minocycline), for example, are ones that do.

Something else to consider: This guarantee of potency and safety applies only if the drug is stored under ideal conditions, as the label instructs. So if you don’t store the drug properly, it’s possible that it may become less effective, ineffective or unsafe even sooner than the expiration date. (More on how to store your drugs properly in a minute.)

SHOULD YOU BE CONCERNED?

It’s important to acknowledge that studies have shown that many drugs maintain full potency and safety long after their expiration dates—even years after. Plus, in my particular situation, I wasted my money but I wasn’t going to die if the pill didn’t help.

When it comes to certain life-sustaining medications, such as nitroglycerine and insulin injections, however, expiration dates become a whole lot more important, because your life depends on those drugs being effective.

The bottom line is that all drugs—especially life-sustaining medications and the antibiotics mentioned earlier—should be stored properly to make sure that they are potent and safe at least through their expiration dates, said Dr. Tiemeier

MAKE YOUR MEDS LAST

Medications should be stored in a cool, dry place where they won’t be subject to big changes in temperature and humidity, said Dr. Tiemeier. Contrary to popular opinion, the bathroom cabinet is usually a terrible place to store medicine, because showers tend to heat up and steam up that room. Leaving pills on the windowsill where the summer sun can beat down on them is also a bad idea—the light ages them. Instead, store your medicines in a cool and dry closet, dresser drawer or kitchen cabinet (not near the heat of an oven or stove).

If you notice a change in how your medicine looks or smells, that may be a sign that the drug has deteriorated, so replace it.

If you’re buying a drug that you’re going to take only on occasion (such as the ibuprofen that I mentioned earlier), look at the expiration date before you buy the bottle and ask yourself whether you’re really going to get through the whole bottle by that date. If not, choose a smaller bottle!

Where do you store your pills? Comment below to share.