Is It Okay to Take Expired Fish Oil?
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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 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, like 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 so-called “bad” (LDL) 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 products were oxidized.

 In addition, 65 percent of the flavored versions and 32 percent of the unflavored versions 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.

 Added flavors can mask the odors that indicate something's off, however.
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).

 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 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, and 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 higher "bad" (LDL) cholesterol and 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.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Fish Oil. Mayo Clinic. August 10, 2023.
  2. Yenipazar H et al. Effect of packaging and encapsulation on the oxidative and sensory stability of omega-3 supplements. Food Science & Nutrition. December 21, 2022.
  3. Kane A. What you should know about supplements, according to an expert. CNN. July 15, 2025.
  4. Tests Find Many Popular Omega 3 Supplements Are Rancid. The George Washington University. September 15, 2023.
  5. Corliss J. The false promise of fish oil supplements. Harvard Health Publishing. December 1, 2023.
  6. Sherratt SCR et al. Are dietary fish oil supplements appropriate for dyslipidemia management? A review of the evidence. Current Opinion in Lipidology. April 2020.
  7. Sherratt SCR et al. Are dietary fish oil supplements appropriate for dyslipidemia management? A review of the evidence. Journal of Dietary Supplements. September 15, 2023.
  8. Sirois J et al. Safety considerations for dietary supplement manufacturers in the United States. Regulatory Toxicology and Pharmacology. December 27, 2023.
  9. Syal R. Revealed: many common omega-3 fish oil supplements are ‘rancid'. The Guardian. January 17, 2022.
  10. Miller K. Revealed: many common omega-3 fish oil supplements are ‘rancid'. Yahoo! Life. September 19, 2023.
  11. Bannenberg G. Advice to Amazon on proper storage and distribution conditions for omega-3 EPA/DHA dietary supplements. Global Organization for EPA and DHa Omega-3s. April 2021.
  12. Omega-3 Fatty Acids. Memorial Sloan Kettering Cancer Center. July 1, 2025.
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Grant Chu, MD, is an assistant clinical professor at the David Geffen School of Medicine at UCLA. Dr. Chu is also the associate director of education at the UCLA Center for East-West Medicine, using technology to further medical education.

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