You already know that fish oil provides support for your heart, joints, and overall mood, and you’re trying to incorporate omega-3 supplements into your diet. You may have heard about, or experienced firsthand, fish oil side effects—most notably those fishy burps. These side effects are normal, but there are a few ways you can reduce symptoms to build a daily supplement routine.
Side effects of fish oil
Like many medications and supplements, fish oil can produce side effects in some individuals. However, most side effects are mild and include the following:
- An unpleasant, fishy taste
- Bad breath
- Bad-smelling sweat
- Belching
- Headache
- Gastrointestinal issues, including heartburn, nausea, and diarrhea1
Some of these fish oil side effects may lessen as your body adjusts to taking the supplement.
Less common side effects
Here are some more serious, but less common, fish oil side effects to be aware of:
- Allergic reaction: Never take fish oil supplements if you are allergic to fish or soy (unless it’s vegan omega-3). Signs of an allergic reaction include difficulty breathing, hives, and swelling of the tongue, lips, or throat. Seek medical attention immediately if you experience these symptoms.
- Low blood pressure: A 2022 study published in the Journal of the American Heart Association showed that an intake of omega-3 can lower blood pressure, which could be problematic for those who already have low blood pressure or are on medication that lowers it2.
- AFib: People with cardiovascular disease or those at high risk may increase their risk of atrial fibrillation if taking very large doses (4,000+ mg) of fish oil daily.
- Reduced immune function: Similarly, prolonged use in high doses may reduce your body’s immune function to fight infections and injuries.
- Vitamin A toxicity: Cod liver oil may have side effects on the kidneys. Cod liver oil supplements contain Vitamin A, which the body stores if you have extra. High levels of accumulation can lead to Vitamin A toxicity, which includes dizziness, nausea, joint pain, skin irritation, and severe headaches3.
You should always talk to your doctor when taking new supplements to ensure proper dosage and avoid medication interactions.
How to reduce fish oil side effects
Gastrointestinal side effects like heartburn and burping are often the most common side effects of fish oil supplements, but there are a few ways to reduce them.
Choose enteric-coated fish oil
When choosing a supplement, look for enteric-coated fish oil capsules. OmegaVia capsules have a special coating that prevents your stomach from immediately dissolving them. Instead, the capsules won’t break down until hitting your intestines. The coating helps minimize the likelihood of burps; however, using enteric-coated fish oil in combination with antacids or heartburn medications, like Pepcid® and Prilosec®, could cause burps.
Take with a meal
The time of day you take omega-3 supplements doesn’t matter quite as much as taking them with a meal. Acid reflux and indigestion (all those fishy burps) often occur because the fish oil will float on top of stomach acid if it’s empty, which then allows acid to come back up the esophagus.
Taking the supplement before eating allows the fish oil to mix with food and pass through to the intestines. It’s also best to take fish oil with food that’s higher in fat, which helps with absorption, so try to incorporate eggs, nuts, or avocados4.
Split up doses
If you’re taking more than one supplement a day, split up the doses. Otherwise, you could experience acid reflux or diarrhea from a higher dosage. Instead, try taking one in the morning and one in the evening, but always take each dose with a meal.
Why choose OmegaVia?
OmegaVia offers a variety of omega-3 supplements to help with heart, joint, brain, and eye support. Our products use ultra-concentrated triglyceride from sustainably sourced sardine, anchovy, and mackerel, so there is no need to worry about the side effects of cod liver oil on the kidneys. The supplements are also purified to remove cholesterol and mercury, making them safe for daily use.
For those worried about heartburn and fishy burps, our fish oil supplements have an enteric coating, so they won’t break down in your stomach.
Frequently asked questions
Can fish oil interact with blood thinners or other medications?
Yes, fish oil can interact with blood thinners when taken in high doses. Fish oil has blood-thinning properties, so taking it with an anticoagulant could extend clotting times. However, research has shown no significant risks in typical doses of 3 to 6 grams per day5.
Manufacturers of these medications include printed advisories of possible medication interactions and recommend that patients work with their doctor to monitor supplement intake and any changes in blood clotting.
Does fish oil cause heartburn or acid reflux?
Yes, fish oil can cause heartburn and acid reflux, which are the most common side effects. When ingested, fish oil can float on top of stomach acid. That stomach acid may come back up your esophagus, causing acid reflux, burping, and heartburn. To reduce these side effects, look for enteric-coated fish oil capsules, which won’t break down until they pass through the intestines.
Also, take fish oil supplements with a meal, preferably with healthy fats to help with nutrient absorption.
What happens when you stop taking fish oil?
There are no withdrawal side effects when you stop taking fish oil. Instead, you can expect a reversal of any benefits from the supplement, so less support for your heart and joints. Fish oil will clear from your bloodstream in just a few days—it has a half-life of about two days. But the omega-3 can remain in your tissues for several weeks6.
Does fish oil cause diarrhea?
Yes, fish oil may cause diarrhea, which is a common side effect. Fish oil has high fat content and, when taken in larger doses, it may cause your colon to secrete more water7. To reduce side effects, take your supplements with a meal. If you’re still having diarrhea, try taking a smaller dosage.
Is it safe to take fish oil every day long-term?
Yes, it’s generally safe to take fish oil every day long-term. As with all supplements, you should talk to your doctor first about the appropriate dosage and how long to take them. More adverse side effects of fish oil supplements usually occur if you’re taking high doses. Taking up to 1 gram per day is considered safe for most adults5.
Sources
- (November 2024). Omega-3 Supplements: What You Need To Know. NCCIH. Retrieved May 20, 2026, from https://www.nccih.nih.gov/health/omega3-supplements-what-you-need-to-know
- Zhang, X., Ritonja, J., Zhou, N., Chen, B., and Li, X. (1 June 2022). Omega‐3 Polyunsaturated Fatty Acids Intake and Blood Pressure: A Dose‐Response Meta‐Analysis of Randomized Controlled Trials. Journal of the American Heart Association. Retrieved May 20, 2026, from https://www.ahajournals.org/doi/full/10.1161/JAHA.121.025071
- Hobbs, H. (February 14, 2025). 9 Little-Known Side Effects of Too Much Fish Oil. Healthline. Retrieved May 20, 2026, from https://www.healthline.com/nutrition/fish-oil-side-effects
- Berger, K. (April 18, 2026). The Best Time to Take Fish Oil Supplements. Verywell Health. Retrieved May 20, 2026, from https://www.verywellhealth.com/time-to-take-fish-oil-8757904
- (August 22, 2025). Omega-3 Fatty Acids. National Institutes of Health. Retrieved May 20, 2026, from https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
- Curtis, L. (December 13, 2025). How Long Does Fish Oil Stay in Your System? Verywell Health. Retrieved May 20, 2026, from https://www.verywellhealth.com/how-long-does-fish-oil-stay-in-your-system-11750167
- Irvine, H. (October 23, 2025). 5 Supplements That Can Cause Diarrhea and How to Prevent It. Everyday Health. Retrieved May 20, 2026, from https://www.everydayhealth.com/nutrients-supplements/supplements-that-cause-diarrhea/
