Fish oil side effects

The most commonly reported side effects of fish oil are mild and gastrointestinal: a fishy aftertaste, burping, and occasional nausea. A systematic review of prescription-strength omega-3 — at doses well above a standard softgel — found these effects showed up more often than with placebo, alongside a couple of minor lab-value changes; it found no clear evidence of any serious treatment-related adverse event.

What the safety data actually covers

A 2018 systematic review and meta-analysis pooled 21 randomized controlled trials of prescription omega-3 products, totaling 24,460 participants. Compared with placebo, the omega-3 groups reported more treatment-related fishy aftertaste (dysgeusia) and skin reactions (eruption, itching, rash or eczema). A subgroup using combined EPA+DHA products specifically reported more burping (eructation) and nausea than placebo. The review also found small changes in some lab values — a slight rise in fasting blood sugar, liver enzymes and blood urea nitrogen, and a slight drop in hemoglobin and hematocrit — and concluded that prescription omega-3 is generally safe and well tolerated but not free of side effects.

Worth naming plainly: this review studied prescription-strength omega-3 products, which use doses well above the 600 mg/day Electric Tiger Omega-3's label directs at two softgels a day. We're citing it because it's the most direct safety data available, not because our softgel has been tested at this level — a lower dose could plausibly produce fewer or milder effects, but nothing in this review establishes that directly.

What tends to help with the fishy aftertaste and burping

Taking a softgel with a meal, rather than on an empty stomach, is the most common practical suggestion — see when is the best time to take fish oil for what the absorption research says about food. Refrigerating softgels is another common suggestion, on the reasoning that a colder capsule dissolves slightly more slowly in the stomach; we haven't found a controlled trial testing that specifically.

Questions people ask

What are the side effects of fish oil?

The most commonly reported are mild and gastrointestinal: fishy aftertaste, burping and occasional nausea. A skin reaction (rash, itching or eczema) was also reported more often than placebo in the safety review above. Serious adverse events were not clearly linked to omega-3 treatment in that review.

Does fish oil upset your stomach?

It can, for some people — burping and mild nausea are the most commonly reported gastrointestinal effects, more so at higher, prescription-strength doses than at typical over-the-counter amounts. Taking it with a meal is the most common way people reduce it.

Can fish oil cause bad breath or burping?

Yes, a fishy aftertaste and burping (eructation) are among the most consistently reported effects across the trials reviewed. They're not dangerous, but they're common enough to be worth knowing about before you start.

Does fish oil affect blood sugar or liver enzymes?

The safety review above found small changes in some lab values — including fasting blood sugar and liver enzymes — at prescription-strength doses, well above what a standard softgel provides. Nothing in that review establishes what, if anything, happens at a 600 mg/day amount.

Related reading: how much fish oil should you take a day, who should not take fish oil, and fish oil and medications: what to check.