Fish oil side effects and safety
Fish oil is LIKELY SAFE for most people when taken by mouth in low doses (3 grams or less per day). There are some safety concerns when fish oil is taken in high doses. Taking more than 3 grams per day might keep blood from clotting and can increase the chance of bleeding.
High doses of fish oil might also reduce the immune system’s activity, reducing the body’s ability to fight infection. This is a special concern for people taking medications to reduce their immune system’s activity (organ transplant patients, for example) and the elderly.
Only take high doses of fish oil while under medical supervision.
Fish oil can cause side effects including belching, bad breath, heartburn, nausea, loose stools, rash, and nosebleeds. Taking fish oil supplements with meals or freezing them can often decrease these side effects.
Fish oil is POSSIBLY SAFE when injected intravenously (by IV) in the short-term. Fish oil or omega-3 fatty acid solutions have been safely used for 1 to 4 weeks.
Consuming large amounts of fish oil from some DIETARY sources is POSSIBLY UNSAFE. Some fish meats (especially shark, king mackerel, and farm-raised salmon) can be contaminated with mercury and other industrial and environmental chemicals. Fish oil supplements typically do not contain these contaminants.
Special Precautions & Warnings:
- Children: Fish oil is POSSIBLY SAFE when taken by mouth appropriately. Fish oil has been used safely through feeding tubes in infants for up to 9 months. But young children should not eat more than two ounces of fish per week. Fish oil is POSSIBLY UNSAFE when consumed from dietary sources in large amounts. Fatty fish contain toxins such as mercury. Eating contaminated fish frequently can cause brain damage, mental retardation, blindness and seizures in children.
- Pregnancy and breast-feeding: Fish oil is LIKELY SAFE when taken by mouth appropriately. Taking fish oil during pregnancy does not seem to affect the fetus or baby while breast-feeding. Women who are pregnant or who may become pregnant, and nursing mothers should avoid shark, swordfish, king mackerel, and tilefish (also called golden bass or golden snapper), as these may contain high levels of mercury. Limit consumption of other fish to 12 ounces/week (about 3 to 4 servings/week). Fish oil is POSSIBLY UNSAFEwhen dietary sources are consumed in large amounts. Fatty fish contain toxins such as mercury.
- Bipolar disorder: Taking fish oil might increase some of the symptoms of this condition.
- Liver disease: Fish oil might increase the risk of bleeding in people with liver scarring due to liver disease.
- Depression: Taking fish oil might increase some of the symptoms of this condition.
- Diabetes: There is some concern that taking high doses of fish oil might make the control of blood sugar more difficult.
- Familial adenomatous polyposis: There is some concern that fish oil might further increase the risk of getting cancer in people with this condition.
- High blood pressure: Fish oil can lower blood pressure and might cause blood pressure to drop too low in people who are being treated with blood pressure-lowering medications.
- HIV/AIDS and other conditions in which the immune system response is lowered: Higher doses of fish oil can lower the body’s immune system response. This could be a problem for people whose immune system is already weak.
- An implanted defibrillator (a surgically placed device to prevent irregular heartbeat): Some, but not all, research suggests that fish oil might increase the risk of irregular heartbeat in patients with an implanted defibrillator. Stay on the safe side by avoiding fish oil supplements.
- Fish or seafood allergy: Some people who are allergic to seafood such as fish might also be allergic to fish oil supplements. There is no reliable information showing how likely people with seafood allergy are to have an allergic reaction to fish oil. Until more is known, advise patients allergic to seafood to avoid or use fish oil supplements cautiously.