Is It Okay to Take Expired Fish Oil?
Diet & NutritionFood & Ingredients

What Happens if You Take Expired Fish Oil?

What Happens if You Take Expired Fish Oil?
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Updated on July 31, 2025
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Fish oil supplements contain cholesterol-regulating and inflammation-fighting omega-3 fatty acids.

 If you’re not a fan of fish, or if you are having trouble finding ways to work it into your diet, fish oil supplements may help.

But when your fish oil supplements have expired, you may wonder whether it’s dangerous if you decide to take them anyway.

What Is Fish Oil?

First, it helps to understand what’s in these supplements: Fish oil contains two omega-3 fatty acids: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Your body can’t make omega-3s on its own, so you have to get them from food, such as salmon, trout, and oysters, or from supplements. Fish oil supplements usually come in pill, capsule, or liquid form.

Your body needs omega-3 fatty acids to carry out a variety of functions, including cell growth and muscle activity. Eating fish can have benefits that supplements don’t provide, such as a lower risk of death from heart disease. But unlike fish, omega-3 supplements made from fish oil appear to contain no mercury.

Does Fish Oil Expire?

Yes. You’ll find the expiration date printed on your bottle of supplements. Time, temperature, air, and light can all cause fish oil to break down via a process called oxidation.

 After the expiration date — or sooner, if they’re stored improperly — fish oil supplements lose potency and will be less effective.

 When fish oil is oxidized at a high enough level, it’s considered rancid.

 If you’re relying on fish oil supplements to keep you healthy, taking an oxidized product, whether it’s before the expiration date or after, could even have harmful effects.

For example, one research review found that taking oxidized fish oil may lead to increased cardiovascular risk. Consuming oxidized fish oil has been linked to an increase in LDL (“bad”) cholesterol, and to vascular changes associated with hardening of the arteries, including inflammation.

Over time, exposure to light, higher than optimal temperatures, and air can cause fish oil supplements to go bad. In one study, researchers examined 72 different omega-3 supplements, including fish oil, and found 68 percent of flavored versions and 13 percent of unflavored ones were oxidized. In addition, 65 percent of the flavored versions and 32 percent of the unflavored ones were found to have high levels of a substance indicating rancidity.

Supplement manufacturers often place a conservative expiration date on their supplements, to reflect the date through which the product is expected to remain at full potency.

 This means in some instances, fish oil supplements may still be effective, though possibly less potent, after they have expired.

Taking expired fish oil supplements is a “do-so-at-your-own-risk” decision. Consult your doctor or registered dietitian for advice.

How to Tell if Fish Oil Has Gone Bad

If your expired fish oil supplements smell bad, don’t take them. Try breaking open a capsule and smelling the liquid: If it smells fishy, it may be rancid.

Fish oil can cause a number of gastrointestinal side effects, including a fishy aftertaste, nausea, and loose stools.

 Taking rancid or expired fish oil supplements may not provide the intended health benefits, and it may worsen side effects.

How to Store Fish Oil

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).

 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): Just toss them in the garbage.

The Takeaway

  • Fish oil supplements contain omega-3 fatty acids (DHA and EPA), which the body needs for essential functions. They also have other health benefits, such as helping to regulate cholesterol and fighting inflammation.
  • They oxidize over time, especially when they’re exposed to higher than optimal temperatures, air, and light, which causes them to lose potency and become less effective.
  • Taking oxidized (rancid) fish oil may have harmful effects, such as contributing to higher LDL cholesterol as well as vascular changes associated with hardening of the arteries.
  • It’s important to store fish oil properly and to avoid taking expired or rancid-smelling supplements, as they may not provide benefits and could worsen side effects.
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Yuying Luo, MD

Medical Reviewer

Yuying Luo, MD, is an assistant professor of medicine at Mount Sinai West and Morningside in New York City. She aims to deliver evidence-based, patient-centered, and holistic care for her patients.

Her clinical and research focus includes patients with disorders of gut-brain interaction such as irritable bowel syndrome and functional dyspepsia; patients with lower gastrointestinal motility (constipation) disorders and defecatory and anorectal disorders (such as dyssynergic defecation); and women’s gastrointestinal health.

She graduated from Harvard with a bachelor's degree in molecular and cellular biology and received her MD from the NYU Grossman School of Medicine. She completed her residency in internal medicine at the Icahn School of Medicine at Mount Sinai, where she was also chief resident. She completed her gastroenterology fellowship at Mount Sinai Hospital and was also chief fellow.

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Sarah Klein is a Boston-based health journalist with more than 15 years experience in lifestyle media. She has held staff positions at Livestrong, Health, Prevention, and Huffington Post. She is a graduate of the Arthur L. Carter Journalism Institute at New York University, and a National Academy of Sports Medicine–certified personal trainer. She moderated a panel on accessibility in fitness at SXSW in 2022, completed the National Press Foundation’s 2020 Vaccine Boot Camp, and attended Mayo Clinic’s Journalist Residency in 2019.

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Resources
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