What Happens to Your Blood Pressure When You Take Fish Oil

Fish oil, which contains omega-3 fatty acids, is found in foods like fatty fish and has been linked to heart health benefits, including reducing triglycerides. But evidence is mixed on whether fish oil supplements significantly reduce blood pressure.

Overall, the research on fish oil and blood pressure is inconsistent. “Some studies have shown that fish oil can help lower blood pressure and others have not,” said Lauren Hynicka, PharmD, BCPS, associate professor of practice, science and health outcomes research at the University of Maryland School of Pharmacy.

A 2022 analysis found that people who consumed 2 to 3 grams of omega-3 fatty acids per day experienced a small average reduction in blood pressure, with the most noticeable effects seen in those who had high blood pressure to begin with. Still, it’s unclear whether fish oil would provide additional benefits to people who already take prescription medications to manage their blood pressure. “Those with normal blood pressure typically see little or no change in their own blood pressure when they take fish oil,” says Michelle Routhenstein, MS, RD, CDCES, CDN, cardiology dietitian at Fully Nourished.

One reason the results are inconsistent is the wide variation among fish oil products on the market, which contain different ratios of the two main types of omega-3, DHA and EPA. Studies also test a range of dosages, some of which appear to have an effect, while others do not. “It is possible that the dose of fish oil makes a difference in the observed effect on blood pressure,” Hynicka said. “But the research is mixed.”

Although there is no conclusive evidence that taking fish oil can lower blood pressure, studies linking fish oil to lower blood pressure suggest that the supplement may help blood vessels relax and widen. In theory, this could decrease inflammation and improve overall blood vessel function, Hynicka said.

Researchers also believe omega-3s reduce oxidative stress, a buildup of free radicals that can damage cells and is thought to contribute to high blood pressure.

Although fish oil is generally well tolerated, it is not without potential side effects. These range from mild problems, like a fishy aftertaste and heartburn, to more serious problems, including an increased risk of atrial fibrillation and stroke. Elevated LDL cholesterol and bleeding complications have also been reported, added Amin Yehya, MD, a cardiologist at Sentara Heart Hospital in Norfolk, Virginia.

It’s also important to know that, unlike prescription medications, supplements are not regulated by the Food and Drug Administration (FDA), meaning they are not approved and evaluated for safety and effectiveness before being released to the market. To ensure quality, experts recommend choosing products that have been tested for purity and accurate labeling by a third-party laboratory.

Because of the relatively high doses required, the risk of side effects and the availability of more effective treatments for hypertension, clinicians do not routinely recommend fish oil supplements, Yehya said. Instead, experts encourage getting omega-3 from food. Oily fish like salmon, mackerel, albacore tuna, trout, and sardines are all good sources, and the American Heart Association suggests two 3.5-ounce servings per week.

For people who don’t eat fish, supplements can fill a gap, Routhenstein said. Still, “nutrition and lifestyle changes are much more effective” in maintaining healthy blood pressure, he said. These include prioritizing sleep, exercising regularly, avoiding risky substances like alcohol, limiting sodium, and managing stress.

As with any supplement, it is best to talk to your doctor or pharmacist before you start consuming fish oil. They “will be able to provide you with information about the risks and benefits of the dietary supplement based on your other health information and help you decide if the supplement is right for you,” Hynicka said.