Skip these 5 household items at Costco—they aren't worth the bargain, says expert at finding deals

When it comes to Costco, it's possible to have too much of a good thing.

That's because the wholesale retailer's low-cost items are often sold in sizes that may be too large to consume before they spoil or go stale, depending on your household size.

Plus, the company doesn't price match with competitors, so you could potentially find lower prices on the same items elsewhere, like at rivals Sam's Club or BJ's Wholesale Club.

To help you determine what's worth buying at Costco and what you can skip, CNBC Make It turned to Julie Ramhold, a consumer analyst at DealNews.com.

Remember that you'll need to purchase a $60 membership to buy almost all items at Costco, which can factor into how much you save. Additionally, prices can vary between Costco locations, and in-store prices tend to be cheaper than what's found online.

Costco's breakfast cereal prices are similar to what you find at other wholesalers, although the selection is limited, says Ramhold.

The store offers brands like Honey Bunches of Oats, Raisin Bran and Cheerios, but doesn't usually have a wide selection of "fun" sugary cereals, she says.

Typically, cereal comes in two-box packages, which means you'll be eating "the same thing over and over to ensure you'll eat it all before it goes stale," says Ramhold. Ready-to-eat cereal lasts about three months after opening, although it starts to go stale much sooner if the packaging isn't tightly sealed.

Lip balm can last a long time, although estimates differ. Some are good for at least a year once opened, while others with natural ingredients like beeswax, shea butter or coconut oil might get hard or clumpy sooner than that.

And most people don't tend to go through stick after stick of lip balm in rapid succession, Ramhold says.

"It may sound like a great idea to buy the lip balm in bulk and have a container for every possible room in your home, plus your vehicle," says Ramhold. "But the truth is that even if you use it habitually, it takes a long time to go through that much lip balm."

For that reason, unless you're buying for family or friends, you probably don't need to grab the nine-count pack of lip balm on Costco shelves. A single stick will do just fine. 

Costco has low-price pain medications compared with many pharmacies, and medicines like aspirin and ibuprofen can last a long time, with expiration dates up to three years, depending on the brand.

However, you simply might not need 1,000 pills of, say, Kirkland Signature brand ibuprofen, unless you have a large household, Ramhold says. For a single person, such a large bottle could take years to finish.

"You probably won't be able to get through an entire bottle of them unless you have chronic pain due to an injury or something like that," says Ramhold. "It's best to speak with your doctor to make sure it's OK to take them that often — some meds can cause liver or stomach issues with prolonged use."

Costco's fresh produce is sold in bulk sizes that are typically larger than what you find in regular grocery stores. 

Considering how quickly produce can spoil, a 25-pound bag of white onions or carton of red tomatoes can be impractical for a shopper without a large family to feed. 

Unless you plan to make a lot of pre-cooked meals in advance, you're likely to waste some of the produce, which would negate the cost savings you'd get from buying in bulk, Ramhold says.

Ground spices have a limited shelf life of about six months, after which they lose their potency. In that case, you probably don't need to buy Costco's five-pound tub of garlic powder, even if it's at a great price.

"For a giant container of chili seasoning, if you're not planning on making chili every single weekend, you probably don't want something that big from Costco," says Ramhold.

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