What Happens if You Take Expired Fish Oil?

Fish oil supplements contain heart-healthy and inflammation-fighting omega-3 fatty acids. If you're having trouble fitting fish into your weekly meals, fish oil supplements can help.

But when your fish oil supplements have expired, you may wonder what happens if you take expired fish oil.

First, it helps to understand what's in those supplements: Fish oil contains two omega-3 fatty acids: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), according to the Mayo Clinic. Your body can't make these omega-3s on its own, so you have to get them from food, like salmon, trout and oysters, or from supplements. The supplements, which usually come in pill, capsule or liquid form, help reduce inflammation.

Yes. You'll find the expiration date printed on your bottle of supplements. Time, temperature, air and light can all cause fish oil to start to break down. After the expiration date, fish oil supplements start to lose potency and may be less effective. And if you're relying on fish oil supplements to keep you healthy, taking an expired product could therefore have harmful effects.

For example, in a small July 2013 ‌International Journal of Food Sciences and Nutrition‌ study, people who took fish oil supplements that had been exposed to air (aka oxidized and going bad) saw their cholesterol levels increase, whereas people who took good fish oil pills saw lower levels.

But if your fish oil supplements have expired, it's also possible they're rancid. Over time, changes in light exposure and temperature can cause fish oil supplements to go bad. In a September 2023 ‌Journal of Dietary Supplements‌ article, researchers examined 72 different fish oil supplements and found 68 percent of flavored versions and 13 percent of unflavored products were oxidized or rancid.

Supplement manufacturers often place a conservative expiration date on their supplements because they take factors like poor storage, time on a shelf and time for the product to be shipped into consideration. This means in some instances, fish oil supplements can still be effective, though possibly less potent, after they have expired.

Therefore, taking expired fish oil supplements is a "do-so-at-your-own-risk" decision. However, if the supplements are significantly past their expiration date — such as one or more years — your risk of experiencing adverse side effects is heightened.

If your expired fish oil supplements smell bad or appear slightly discolored, do not take them. Try breaking open a capsule and smelling the liquid: If it smells like fish, it's likely rancid, according to the Arthritis Foundation. A fishy taste when you take your supplements is also a sign they've gone bad, per Nordic Naturals.

Fish oil can cause a number of stomach-related side effects, including fish oil burps, nausea and loose stools. Taking rancid, expired fish oil supplements can worsen side effects, per the Arthritis Foundation.

Even if your fish oil supplements haven't expired, they can still go bad if you store them improperly.

Store fish oil at room temperature, out of direct sunlight and somewhere dry (aka not the bathroom), according to Memorial Sloan Kettering Cancer Center (MSKCC). Some fish oil shouldn't be frozen; others you can pop in the freezer to keep them fresh for longer. Always refer to the product's label for storage tips.

And when it comes to what to do with expired fish oil capsules (even unopened expired fish oil), toss it in the garbage, per MSKCC.