Both fish oil and magnesium have a number of health benefits. Taking fish oil supplements may help lower your triglycerides, ease inflammation and pain, and lower blood pressure. Magnesium supplements may also help reduce your blood pressure, as well as manage your calcium levels and prevent hardening of the blood vessels.
Because these supplements have some overlapping effects, it’s important to speak with your doctor before taking the two together. Taking them at the same time may lead to too much of a good thing, such as causing your blood pressure to drop too low and uncomfortable symptoms.
How Do Fish Oil and Magnesium Interact?
Fish oil can help lower your triglycerides and begin to clear out your arteries, causing your blood pressure to decrease, according to Mayo Clinic. Magnesium is considered a natural calcium channel blocker, meaning it prevents calcium from building up in your arteries. In fact, it may help your arteries relax and open up, and potentially lower your blood pressure.
Taking both fish oil and magnesium supplements at the same time may lower your blood pressure even more. Low blood pressure may cause you to feel dizzy, lightheaded, weak, and even confused, says Cleveland Clinic.
For this reason, it’s important to talk with your doctor about potential interactions between fish oil and magnesium supplements before you take them at the same time. You may be able to space them out during the day instead.
Overall, the risk of interaction between fish oil and magnesium is more theoretical, since both fish oil and magnesium on their own are known to mildly lower blood pressure. In fact, various drug interaction checkers, as well as Mayo Clinic and the National Institutes of Health (NIH), for example, do not list the two as having a possible interaction.
But if you already have low blood pressure, it’s best to speak with your doctor before starting either, and especially if you plan to take them together.
The Benefits of Fish Oil
Omega-3 fatty acids are healthy fats found in fish like salmon and mackerel, as well as fish oil supplements. They’re not produced by your body, but they’re important for various bodily processes, such as helping your cells grow and your muscles function, as well as lowering blood pressure, says Mayo Clinic. They can also play an important role in:
- Lowering triglyceride and cholesterol levels: The omega-3 fatty acids in fish oil can significantly lower the levels of fatty substances called triglycerides in your blood, says Mayo Clinic. These substances clog your arteries over time, forming hard plaque that makes it harder for blood from your heart to flow through your blood vessels. Omega-3 fatty acids can also lower LDL (“bad”) cholesterol levels while improving HDL (“good”) cholesterol.
- Reducing arterial plaque: Fish oil may help remove plaque that forms in your arteries and can prevent it from forming, according to research published in 2020. This allows blood to flow more easily throughout your body.
- Easing inflammation: Fish oil can help reduce pain associated with inflammation in your joints, says the Arthritis Foundation. It may also help you feel less achy and stiff in the morning and even lessen the need for anti-inflammatory medications, says Mayo Clinic.
- Improving mood: Research published in 2023 suggests that omega-3s, which are found in fish oil, may reduce symptoms of depression.
Fish oil is generally safe to take, and any side effects you may experience are mild and temporary, according to Mayo Clinic. These side effects can include a taste akin to fish in your mouth, belching, and nausea.
It’s also possible for fish oil to interact with other medications, including anticoagulant and blood pressure medications, so it’s important to speak with your doctor first before taking it as a supplement.
The Benefits of Magnesium
Magnesium has a number of health benefits, according to Cleveland Clinic. It can support healthy digestion, ease stress and anxiety, and relieve sore, achy muscles. It also plays a role in:
- Improving heart beat: Magnesium helps your heart beat consistently, says the Keck Medicine of USC. Too low levels can contribute to irregular heartbeats.
- Reducing the risk of cardiac events: Research published in 2025 suggests that magnesium supplements can reduce the risk of heart failure and major cardiac events, such as heart attack and stroke, in people with diabetes.
- Lowering blood pressure: Calcium can affect the way your heart beats and may contribute to high blood pressure. It can build up in your arteries, contributing to calcification or hardening in your blood vessels, says the British Heart Foundation. Increasing your intake of magnesium can help prevent this hardening, which is a predictor of heart attack or stroke, according to research published in 2022. Magnesium acts as a natural calcium channel blocker or antihypertensive medication.
While magnesium supplements are considered safe, you may experience some mild side effects, such as nausea or mild diarrhea, upon taking them, according to Harvard Health Publishing. Getting magnesium through food sources — such as spinach and other leafy greens, legumes, nuts, and whole grains — doesn’t cause these side effects, though, says the Office of Dietary Supplements.
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