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Fish oil comes from many types of fish. It is rich in two important omega-3 fatty acids called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
The benefits of fish oil seem to come from its omega-3 fatty acid content. Fish that are especially rich in these oils include mackerel, herring, tuna, and salmon. The body doesn't produce many of its own omega-3 fatty acids. Omega-3 fatty acids reduce pain and swelling, and also prevent the blood from clotting easily.
Some fish oil products are approved by the FDA as prescription medications to lower triglycerides levels. Fish oil is also available as a supplement. Fish oil supplements do not contain the same amount of fish oil as prescription products, so they cannot be used in place of prescription products. Fish oil supplements are sometimes used for heart health and mental health, but there is no strong evidence to support most of these uses.
Do not confuse fish oil with EPA, DHA, cod liver oil, flaxseed oil, krill oil, or shark liver oil. See the separate listings for these topics.
- Hypertriglyceridemia. Oral prescription fish oil products reduce triglyceride levels in patients with hypertriglyceridemia, especially in severe cases. Oral fish oil supplements may reduce triglyceride levels when used in very high doses of up to 12 capsules per dose.
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- Angioplasty. Oral fish oil seems to prevent restenosis when started at least 3 weeks before percutaneous transluminal coronary angioplasty (PTCA).
Login for details - Cachexia. Oral fish oil in doses of 7.5-8.1 grams daily seems to slow weight loss in patients with cachexia. Lower doses might not be effective.
Login for details - Cyclosporine-induced nephrotoxicity. Oral fish oil seems to prevent cyclosporine-induced nephrotoxicity.
Login for details - Dysmenorrhea. Oral fish oil seems to reduce symptoms of dysmenorrhea.
Login for details - Heart failure. Dietary fish oil seems to prevent heart failure. Also, oral fish oil seems to prevent further hospitalization, and possibly mortality, in patients with heart failure.
Login for details - HIV/AIDS-related dyslipidemia. Oral fish oil seems to reduce triglyceride levels in patients with this condition. It is unclear if oral fish oil reduces levels of low-density lipoprotein (LDL) cholesterol in these patients.
Login for details - Hypertension. Oral fish oil seems to reduce systolic and diastolic blood pressure in adults with moderate or severe hypertension. It is unclear if oral fish oil reduces blood pressure in patients with mild hypertension or in those using antihypertensive drugs.
Login for details - IgA nephropathy. When used for 2-4 years, oral fish oil seems to slow the rate of renal function loss in high-risk patients. It is unclear if oral fish oil slows renal function loss when used for shorter time points or in low-risk patients.
Login for details - Nonalcoholic fatty liver disease (NAFLD). Oral fish oil seems to reduce liver steatosis in adults and children with NAFLD.
Login for details - Rheumatoid arthritis (RA). Oral and intravenous fish oil seem to reduce pain and stiffness in patients with RA.
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- Age-related macular degeneration (AMD). Oral fish oil does not seem to prevent the incidence of AMD or its progression. However, eating fish regularly might reduce the risk of AMD.
Login for details - Angina. Oral fish oil does not seem to improve cardiovascular outcomes in patients with angina.
Login for details - Atherosclerosis. Oral fish oil does not seem to attenuate atherosclerosis progression.
Login for details - Atopic dermatitis (eczema). Oral fish oil does not seem to treat or prevent atopic dermatitis.
Login for details - Atrial fibrillation. Oral fish oil does not seem to reduce the risk of new or recurrent atrial fibrillation. Some clinical research suggests that high-dose fish oil may actually increase the risk for new atrial fibrillation.
Login for details - Bipolar disorder. Oral fish oil does not seem to prevent mood relapses or improve symptoms in patients with bipolar disorder.
Login for details - Bronchopulmonary dysplasia. Oral fish oil does not seem to prevent bronchopulmonary dysplasia in preterm infants.
Login for details - Cerebrovascular disease. Oral fish oil does not seem to prevent cerebrovascular disease.
Login for details - Cognitive function. Oral fish oil does not seem to improve cognitive function in most people.
Login for details - Helicobacter pylori. Oral fish oil does not seem to aid in the Helicobacter pylori eradication.
Login for details - Kidney transplant. Oral fish oil does not seem to improve survival or rejection rates following a kidney transplant.
Login for details - Mastalgia. Oral fish oil does not seem to reduce chronic breast pain.
Login for details - Multiple sclerosis (MS). Oral fish oil does not seem to improve symptoms in patients with MS.
Login for details - Osteoarthritis. Oral fish oil does not seem to improve pain or function in patients with osteoarthritis. However, oral fish oil might be beneficial for osteoarthritis-related joint pain in overweight patients.
Login for details - Pregnancy-induced hypertension. Oral fish oil does not seem to reduce the risk for hypertension during pregnancy.
Login for details - Pre-eclampsia. Oral fish oil does not seem to reduce the risk of pre-eclampsia.
Login for details - Sarcopenia. Oral fish oil does not seem to improve muscle strength in older adults with sarcopenia.
Login for details - Ventricular arrhythmias. Oral fish oil does not seem to prevent ventricular arrhythmias or prevent mortality in patients with a history of ventricular arrhythmias.
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- Diabetes. Oral fish oil does not improve glycemic control or prevent cardiovascular outcomes in patients with type 2 diabetes. However, oral fish oil may lower triglyceride levels in patients with type 2 diabetes.
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- Acute respiratory distress syndrome (ARDS). It is unclear if enteral or intravenous fish oil is beneficial in patients with ARDS.
Login for details - Age-related cognitive decline. It is unclear if oral fish oil prevents age-related cognitive decline.
Login for details - Allergic rhinitis (hay fever). It is unclear if taking oral fish oil during pregnancy prevents allergic rhinitis in the child.
Login for details - Alzheimer disease. It is unclear if oral fish oil is beneficial for preventing Alzheimer disease or for improving cognition in those with this condition.
Login for details - Antiphospholipid syndrome-associated miscarriage. It is unclear if oral fish oil prevents miscarriage in patients with antiphospholipid syndrome.
Login for details - Antipsychotic-induced metabolic side effects. It is unclear if oral fish oil is beneficial for metabolic side effects related to the use of olanzapine.
Login for details - Asthma. It is unclear if oral fish oil prevents or treats asthma.
Login for details - Athletic performance. It is unclear if oral fish oil improves athletic performance.
Login for details - Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral fish oil is beneficial in patients with ADHD.
Login for details - Autism spectrum disorder. It is unclear if oral fish oil is beneficial in patients with autism spectrum disorder.
Login for details - Borderline personality disorder. It is unclear if oral fish oil is beneficial for borderline personality disorder.
Login for details - Cancer. It is unclear if dietary or supplemental fish oil can reduce the risk for cancer.
Login for details - Canker sores. It is unclear if oral fish oil is beneficial for preventing or treating canker sores.
Login for details - Cardiovascular disease (CVD). The effect of fish oil on cardiovascular health is controversial. Oral fish oil in doses of up to 4 grams daily does not seem to be beneficial for primary or secondary prevention of CVD. It is unclear whether dietary fish oil or a higher daily dose is beneficial for prevention of CVD.
Login for details - Cataracts. It is unclear if oral fish oil prevents the development of cataracts.
Login for details - Chemotherapy-induced peripheral neuropathy. It is unclear if oral fish oil is beneficial for the prevention of peripheral neuropathy in patients receiving chemotherapy.
Login for details - Chronic kidney disease (CKD). It is unclear if oral fish oil is beneficial in patients with CKD.
Login for details - Chronic obstructive pulmonary disease (COPD). It is unclear if oral fish oil is beneficial in patients with COPD.
Login for details - Cirrhosis. It is unclear if oral fish oil is beneficial in patients with cirrhosis.
Login for details - Cognitive impairment. It is unclear if oral fish oil prevents or treats cognitive impairment.
Login for details - Colorectal cancer. It is unclear if oral fish oil prevents or treats colorectal cancer.
Login for details - Coronary artery bypass graft (CABG) surgery. It is unclear if oral fish oil is beneficial following CABG surgery.
Login for details - Crohn disease. It is unclear if oral fish oil is beneficial for reducing the risk for relapse in patients with Crohn disease who are in remission; the available evidence is conflicting.
Login for details - Cyclosporine-induced hypertension. Small clinical studies suggest that oral fish oil may prevent or modestly improve symptoms in patients with cyclosporine-induced hypertension.
Login for details - Cystic fibrosis. It is unclear if oral or intravenous fish oil is beneficial in patients with cystic fibrosis.
Login for details - Dementia. It is unclear if oral fish oil prevents dementia.
Login for details - Depression. It is unclear if oral fish oil is beneficial in patients with depression. There is some evidence that benefits vary depending on the form of fish oil used and the patient population studied.
Login for details - Developmental coordination disorder (DCD). Oral fish oil has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Diabetic nephropathy. It is unclear if oral fish oil is beneficial in patients with diabetic nephropathy.
Login for details - Diabetic neuropathy. It is unclear if oral fish oil is beneficial for the treatment or prevention of neuropathy in patients with type 1 diabetes.
Login for details - Diabetic retinopathy. It is unclear if oral fish oil is beneficial in patients with diabetic retinopathy.
Login for details - Dry eye. It is unclear if oral fish oil is beneficial in patients with dry eye.
Login for details - Dyslexia. It is unclear if oral fish oil is beneficial in patients with dyslexia.
Login for details - Dyslipidemia. It is unclear if oral fish oil is beneficial in patients with dyslipidemia.
Login for details - Endometrial cancer. It is unclear if oral fish oil reduces the risk for endometrial cancer.
Login for details - Endometriosis. It is unclear if oral fish oil is beneficial in patients with endometriosis.
Login for details - Epilepsy. Some clinical research suggests that oral omega-3 fatty acids may modestly reduce seizure frequency in patients with epilepsy. However, it is unclear if oral fish oil itself is beneficial in patients with epilepsy.
Login for details - Exercise-induced muscle soreness. It is unclear if oral fish oil reduces the severity of exercise-induced muscle soreness.
Login for details - Food allergies. It is unclear if oral fish oil is beneficial in patients with food allergies.
Login for details - Gingivitis. It is unclear if oral fish oil is beneficial in patients with gingivitis.
Login for details - Glaucoma. Login for details
- Hemodialysis graft dysfunction. It is unclear if oral fish oil is beneficial in patients with hemodialysis graft dysfunction.
Login for details - Heart transplant. It is unclear if oral fish oil is beneficial in patients after a heart transplant.
Login for details - HIV/AIDS. It is unclear if oral fish oil is beneficial for HIV.
Login for details - Impaired glucose tolerance (prediabetes). It is unclear if oral fish oil is beneficial for impaired glucose tolerance.
Login for details - Infant development. It is unclear if oral fish oil, taken during pregnancy or by the infant, is beneficial for improving vision or cognitive development in infants.
Login for details - Insomnia. It is unclear if oral fish oil is beneficial for insomnia.
Login for details - Intrauterine growth restriction (IUGR). Login for details
- Joint pain. It is unclear if oral fish oil is beneficial for joint pain.
Login for details - Kidney failure. Small clinical studies in adults with kidney failure suggest that oral fish oil may modestly improve some blood lipid and inflammatory marker levels.
Login for details - Lyme disease. Login for details
- Male infertility. It is unclear if oral fish oil is beneficial for male infertility.
Login for details - Menopausal symptoms. It is unclear if oral fish oil is beneficial for menopausal symptoms.
Login for details - Migraine headache. Supplemental fish oil does not seem to reduce the frequency or severity of migraine headaches. However, dietary fish oil may reduce the frequency and duration of migraine headaches.
Login for details - Obesity. Most clinical research shows that fish oil supplements do not improve weight loss; however, dietary fish intake might be beneficial for obesity. It is unclear if fish oil is beneficial for improving cardiometabolic risk factors in overweight or obese children.
Login for details - Oral mucositis. It is unclear if oral fish oil is beneficial for oral mucositis.
Login for details - Osteoporosis. Oral fish oil has predominantly been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Pancreatitis. Small clinical studies suggest that parenteral fish oil may modestly benefit patients with pancreatitis. It is unclear if oral fish oil is beneficial for pancreatitis.
Login for details - Peripheral arterial disease (PAD). It is unclear if oral fish oil is beneficial for PAD.
Login for details - Periodontitis. It is unclear if oral fish oil is beneficial for periodontitis.
Login for details - Phenylketonuria (PKU). Small clinical studies suggest that oral fish oil may modestly improve symptoms in patients with PKU.
Login for details - Pneumonia. It is unclear if oral fish oil is beneficial for pneumonia.
Login for details - Post-traumatic stress disorder (PTSD). It is unclear if oral fish oil is beneficial for PTSD.
Login for details - Postpartum depression. It is unclear if oral fish oil is beneficial for postpartum depression.
Login for details - Preterm labor. Research on the use of oral fish oil for the prevention of preterm labor is conflicting; however, there may be benefit of oral fish oil in patients with low baseline omega-3 status.
Login for details - Prematurity. It is unclear if oral fish oil is beneficial for improving the development of premature infants.
Login for details - Pressure ulcers. It is unclear if enteral, parenteral, or topical fish oil is beneficial in patients with pressure ulcers.
Login for details - Psoriasis. It is unclear if oral or topical fish oil is beneficial in patients with psoriasis. Intravenous fish oil seems to reduce symptoms in patients with acute, extended guttate psoriasis or chronic plaque psoriasis.
Login for details - Psychosis. Evidence on the use of oral fish oil for psychosis prevention is conflicting.
Login for details - Raynaud syndrome. It is unclear if oral fish oil is beneficial in patients with this condition.
Login for details - Respiratory tract infections. It is unclear if oral fish oil prevents respiratory tract infections.
Login for details - Salicylate intolerance. It is unclear if oral fish oil is beneficial in patients with salicylate intolerance.
Login for details - Schizophrenia. It is unclear if oral fish oil is beneficial in patients with schizophrenia.
Login for details - Sepsis. It is unclear if oral fish oil is beneficial in patients with sepsis.
Login for details - Sickle cell disease. It is unclear if oral fish oil is beneficial in patients with sickle cell disease.
Login for details - Stroke. It is unclear if oral fish oil is beneficial in the secondary prevention of stroke or for improving recovery from a stroke. Oral supplemental fish oil does not seem to be beneficial in the primary prevention of stroke.
Login for details - Systemic lupus erythematosus (SLE). It is unclear if oral fish oil is beneficial in patients with SLE.
Login for details - Ulcerative colitis. It is unclear if oral fish oil is beneficial in patients with ulcerative colitis.
Login for details - Venous thromboembolism (VTE). It is unclear if dietary fish or omega-3 fatty acids are beneficial in VTE prevention.
Login for details - Vitamin D deficiency. It is unclear if fish oil is beneficial for vitamin D deficiency.
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When taken by mouth: Fish oil is likely safe for most people in doses of 3 grams or less daily. Taking more than 3 grams daily might increase the chance of bleeding. Fish oil side effects include heartburn, loose stools, and nosebleeds. Taking fish oil supplements with meals or freezing them can reduce these issues.
Consuming high amounts of fish oil from DIETARY sources is possibly unsafe. Some fish are contaminated with mercury and other chemicals. Fish oil supplements typically do not contain these chemicals.
When applied to the skin: There isn't enough reliable information to know if fish oil is safe or what the side effects might be.
Special Precautions & Warnings:
Pregnancy and breast-feeding: Fish oil supplements are likely safe when taken by mouth. Taking fish oil does not seem to affect the fetus during pregnancy or the baby while breast-feeding. But shark, swordfish, king mackerel, and tilefish should be avoided during pregnancy, by those who may become pregnant, and while breast-feeding. These fish might contain high levels of mercury and may contain other toxins. Limit consumption of other fish to 12 ounces/week (about 3 to 4 servings/week). Consuming fatty fish in high amounts is possibly unsafe.Children: Fish oil supplements are possibly safe when taken by mouth. In adolescents, fish oil has been used safely in doses of up to about 2.2 grams daily for 12 weeks. But young children should not eat more than two ounces of fish per week. Consuming fish oil from DIETARY sources in large amounts is possibly unsafe. Fatty fish contain toxins such as mercury. Eating contaminated fish frequently can cause serious adverse effects in children.
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.
Diabetes: Taking high doses of fish oil might make it more difficult to control blood sugar levels.
Familial adenomatous polyposis: There is some concern that fish oil might further increase the risk of getting cancer in people with this condition.
Conditions in which the immune system response is lowered (including HIV/AIDS): 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 device to prevent irregular heartbeat: Fish oil might increase the risk of irregular heartbeat in patients with an implanted defibrillator. Stay on the safe side and avoid 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.
Birth control pills (Contraceptive drugs)
Interaction Rating=Moderate Be cautious with this combination.
Fish oils seem to help reduce some fat levels in the blood. These fats are called triglycerides. Birth control pills might decrease the effectiveness of fish oils by reducing these fat levels in the blood.
Medications for high blood pressure (Antihypertensive drugs)
Interaction Rating=Moderate Be cautious with this combination.
Fish oils seem to decrease blood pressure. Taking fish oils along with medications for high blood pressure might cause your blood pressure to go too low.
Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)
Interaction Rating=Minor Be watchful with this combination.
Fish oils might slow blood clotting. Taking fish oils along with medications that also slow clotting might increase the chances of bruising and bleeding.
Orlistat (Xenical, Alli)
Interaction Rating=Moderate Be cautious with this combination.
Orlistat (Xenical, Alli) is used for weight loss. It prevents dietary fats from being absorbed from the gut. There is some concern that orlistat (Xenical, Alli) might also decrease absorption of fish oil when they are taken together. To avoid this potential interaction take orlistat (Xenical, Alli) and fish oil at least 2 hours apart.
Herbs and supplements that might lower blood pressure: Fish oil might lower blood pressure. Taking it with other supplements that have the same effect might cause blood pressure to drop too much. Examples of supplements with this effect include andrographis, casein peptides, L-arginine, niacin, and stinging nettle.
Herbs and supplements that might slow blood clotting: Fish oil might slow blood clotting and increase the risk of bleeding. Taking it with other supplements with similar effects might increase the risk of bleeding in some people. Examples of supplements with this effect include garlic, ginger, ginkgo, nattokinase, and Panax ginseng.
Vitamin D: Taking fish oil may increase vitamin D levels. This seems to only occur in people who have low vitamin D levels.
Vitamin E: Fish oil might reduce vitamin E levels. Researchers aren't sure if this is because fish oil keeps vitamin E from being absorbed from food or because it causes the body to use up vitamin E faster than it should.
There are no known interactions with foods.
Fish oil supplements have most often been used by adults in doses of up to 6 grams daily by mouth for up to 12 weeks. Fish oil products typically provide 180-465 mg of EPA and 120-375 mg of DHA per capsule. Fish oil is also available in prescription drugs, including Lovaza, Omtryg, and Epanova. Fish oil supplements cannot be used in place of fish oil prescription drugs. Speak with a healthcare provider to find out what product and dose might be best for a specific condition.
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