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Side Effects

Risk of Side Effects from Ingestion of Omega-3 Fatty Acids, Per Dosage

Up to 1 g/day 1 to 3 g/day More than 3g/day
Fishy Aftertaste Low Moderate Likely
Gastrointestinal Upset Very low Moderate Moderate

The Most Common Side Effect of Fish Oil is Fishy Aftertaste

  • In the GISSI Prevention study, which provided 850 mg of Omega-3 fatty acids per day for 3.5 years,
    • 3.8% of patients discontinued taking their supplements compared with 2.1 taking Vit E
    • Gastrointestinal disturbance and nausea were the most commonly reported side effects, with 4.9% and 1.4% reported, respectively, compared with 2.9% and 0.4% in the Vit E group
  • When 12 capsules containing 6g of Omega-3 fatty acids were fed to 41 patients for 2.4 years, three patients (7% of patients) dropped from the study claiming intolerance to the capsules
  • In a 6-month trial providing 275 patients with 6.9g of EPA + DHA in 10 capsules daily, there was no difference between fish oil and corn oil control groups for any adverse events/
    • Gastrointestinal upset was reported by 8% of the latter and 7% of the former.


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  1. One school says it is easier for body to convert EPA into DHA. Other says it is easier for body to convert DHA into EPA by removing 2 bonds. Adding 2 bonds for conversion from EPA to DHA is difficult.
    First school of thoughts says Fish oil with EPA and DHA should not be taken. DHA will neutralise EPA. Only excess of EPA over DHA will be useful for body.It says body needs DHA only upto 2 yrs of age. Adults should use only EPAOmega 3 WITHOUT DHA
    Other school says higher the DHA the better for the adults.
    There is lot of conflicting literature.
    Will you please clarify on this ?

    • Hi Deepak – there is indeed a lot of conflicting information on the internet. It is after all, the internet, where anyone with a laptop and an opinion is an expert. I understand that I am not exempt from this criticism.

      Having said that, I feel pretty confident in saying that retroconversion of DHA to EPA is relatively easier because it requires less of the body.
      You need DHA well past age 2.

      • I have been taking 2,000 mg. of fish oil for a couple of years now. I am getting a yellow film on my skin AND oily hair. Could this be the fish oil?

        • Hi Valerie – it is possible. It could also be some of the other things you are consuming.

          How concentrated is your fish oil? In other words, out of the 2000 mg of fish oil, how much is Omega-3? The reason you’re taking all that oil is for the Omegas. You can take a different brand with more Omega per pill…you don’t have to buy our ultra high concentration products, but you can select a good one with 80%+ Omega-3 at IFOS Consumer Reports.

  2. Hi Norma – Omega-3 does not impact cholesterol levels that much. It will improve triglyceride levels (another type of fat in the blood) and it will lower inflammation. 2400 mg Omega-3 is a moderate dose. Any side effects you feel from this is probably related to digestive discomfort. It should be temporary and harmless.

  3. Hi Martha – fish oil’s Omega-3 benefits will subside in a couple of weeks as the EPA Omega- 3 gets processed out. The DHA in fish oil will stay in the body for much longer, but that will not cause any bleeding risks. My suggestion is to stop taking it for 2 weeks. Buy another brand and take 2000 mg of Omega-3 per day instead. If the bleeding continues, talk to your doctor, as it is probably something else.

  4. Hi.. My mother has hemophilia A she didnt know the doctor who gave her medicine has fishoil in it. Now she has been suffering from nose bleeds and it has been five days that she is going to hospital. Please guide us how to reduce these already prevailing effects she has got. She had imediately stopped taking the pill. But still the side effect in the blood was there. Thank you

    • Hi Tak Yam – hemophilia is a serious medical condition. We cannot provide medical advice. For normal healthy people, fish oil does not cause bleeding issues if taken as directed. However, this is a different situation. Please work with your doctor to ensure proper care.

    • My boyfriend has and odor from taking fish oil pills I am trying to find a way to counter act the smell of anyone knows something that could help I would greatly appreciate it.

      • Hi Rai – I suggest discontinuing the Omega-3 supplement for two weeks and start with a different brand or source of Omega-3.

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