Here's What You Should Know Before Taking Magnesium and Fish Oil Together

Fish oil and magnesium are two popular supplements used for a variety of reasons. Fish oil is beneficial in providing energy, as well as in helping with heart, lung, and immune system functioning. Magnesium is used in many important body processes, including managing blood sugar levels, blood pressure, and muscle and nerve function. 

Your body does not naturally make fish oil or magnesium, and both must be obtained through your diet. Some people consume enough fish oil and magnesium through food and beverages. However, other people may require supplements to help meet their daily needs. 

Based on your individual health needs, your healthcare provider may recommend you take supplements for both fish oil and magnesium.

Fish oil is a natural product that comes from a variety of oily fish, such as salmon, trout, and anchovies. Fish oil supplements provide omega-3 fatty acids, specifically eicosatetraenoic acid (EPA) and docosahexaenoic acid (DHA). Omega-3 fatty acids help give your body energy and also help with functions in the heart, lungs, immune system, and other parts of the body.

Fish oil supplements can be used to help prevent and treat many health conditions. Some of the potential benefits of fish oil supplements include that they can:

• Promote heart health: Fish oil helps keep your heart healthy, protecting against issues like high blood pressure (hypertension), stroke, and high cholesterol (hyperlipidemia).
• Reduce triglycerides: Fish oil has also been shown to reduce triglyceride levels. Triglycerides are a type of fat found in the blood that can raise your risk of heart disease. Fish oil helps remove plaque caused by triglycerides, which allows blood to flow more freely and blood pressure to decrease.
• Prevent cancer: Fish oil and omega-3 supplements may reduce the risk of breast cancer and colorectal cancer.
• Manage inflammation: Fish oil can improve inflammation and may relieve pain caused by inflammation, especially in people with rheumatoid arthritis.
• Protect cognitive function: Fish oil may lower the risk of developing Alzheimer’s disease, dementia, and other cognitive function problems. 
• Prevent eye degeneration: Fish oil supplements may decrease the risk of developing age-related macular degeneration (AMD). AMD is a common cause of vision loss for older adults. 
• Improve mental health: Fish oil may also help reduce anxiety and depression symptoms.

Magnesium is necessary for the proper function of many processes in the body, including mineral absorption, muscle and nerve function, and DNA production. Magnesium can be found in many foods, such as green leafy vegetables, fortified breakfast cereals, nuts, seeds, and various dairy products. However, it's estimated that half of Americans ingest less magnesium from food than recommended.

Magnesium supplements may be necessary for people who don't consume enough magnesium in their diet. Taking magnesium has been shown to help with multiple health conditions. Magnesium supplements may benefit you in the following ways:

• Promote heart health: Magnesium supplements may decrease blood pressure, which in turn lowers your risk of heart disease and stroke. However, research shows magnesium decreases blood pressure by only a small amount, so people with hypertension may see a benefit if they take magnesium with other blood pressure-lowering medications.
• Manage blood sugar: Magnesium helps the body break down sugar, which may help reduce the risk of insulin resistance and the chances of developing type 2 diabetes. 
• Promote bone health: Magnesium is important for bone health, reducing the risk of bone fractures and osteoporosis in certain populations.
• Manage migraine: Magnesium supplements can reduce the frequency of migraine headaches. 
• Improve mental health: Magnesium supplements may help lower symptoms related to stress and anxiety. 

There are multiple types of magnesium, and some may be better at treating certain symptoms or health conditions than others. The magnesium supplement forms most easily absorbed by the body are magnesium aspartate, magnesium citrate, magnesium lactate, and magnesium chloride.

Taking fish oil and magnesium together may be beneficial to people with certain health conditions, particularly when it comes to heart and brain health. 

Since fish oil helps lower triglyceride levels and plaque buildup, the supplement may improve overall blood flow and help decrease blood pressure. Magnesium also helps open the blood vessels, which may further contribute to lowering blood pressure. Therefore, people with heart conditions and high blood pressure may see compounded benefits by taking fish oil and magnesium together. 

Fish oil and magnesium have also been shown to improve mental health. Therefore, taking both supplements may be especially beneficial for people with anxiety or depression.

Fish oil and magnesium are not available as one combination product. 

Fish oil supplements can be purchased in either a softgel capsule or liquid form and are taken by mouth. Fish oil supplements are available as a single product, in combination with other fish products (such as krill oil), or as a part of a multivitamin. You can take fish oil supplements at any time of the day, depending on when works best for you.

Magnesium supplements can be purchased in various forms, including capsules, tablets, powders, and liquids. They're available as a single product, in combination with other supplements, or as part of a multivitamin. Magnesium within a supplement varies, and some types may be better at treating certain symptoms or health conditions than others. You can take magnesium supplements at any time of the day, depending on when works best for you.

Dosage

Your dosage for fish oil and magnesium and how long you should take each at that dosage can depend on factors like your current levels of both, health conditions you may have, and your diet. 

The amount of fish oil a supplement has varies depending on the product. Typically, a fish oil supplement provides about 1,000 milligrams (mg) of fish oil. That amount usually has 180 mg of EPA and 120 mg of DHA. In studies, fish oil has most often been used in doses up to 6 grams (g) a day for up to 12 weeks, though lower doses have been used for longer. 

When selecting a dosage, you’ll want to consider the daily recommended values (DV) of EPA and DHA. The U.S. Food and Drug Administration (FDA) recommends no more than 5 g of EPA and DHA combined from dietary supplements per day. You likely won’t reach that amount in fish oil supplements alone, but if you have heart disease, know that the recommended intake of EPA plus DHA is no more than 1 g in diet and supplements combined. 

The amount of magnesium in a supplement also varies depending on the product, as does the type of magnesium. The daily recommended value for magnesium—from combined food and supplement sources—depends on your age and sex:

• Men: 400 mg if you are 19-30, 420 mg if you are 31 or older
• Women: 310 mg if you are 19-30, 320 mg if you are 31 or older
• Pregnant people: 40 mg

Be sure to follow all dosage directions from your healthcare provider and the drug manufacturer.

It appears largely safe to take fish oil and magnesium together.

A complication that could theoretically happen is the supplement combination lowers your blood pressure too much. But since fish oil and magnesium appear to decrease blood pressure only by a small amount compared with blood pressure-lowering medications, the likelihood is low that this would be a significant concern.

Still, people with low blood pressure (hypotension) or who are taking blood pressure-lowering medications should be cautious when taking the two blood pressure-lowering supplements. 

Symptoms of low blood pressure include dizziness, lightheadedness, nausea, and confusion.

Potential Drug Interactions

Fish oil and magnesium may each interact with medications you are already taking. Examples of medications that fish oil supplements can interact with include:

• Anticoagulants: Fish oil may increase the risk of bleeding if taken with blood thinners such as warfarin (sold under brand names like Antoven and Coumadin). 
• Antihypertensives: Since fish oil may lower your blood pressure, taking the supplement with medications used to treat high blood pressure might lower your blood pressure too much and cause hypotension.
• Contraceptives: Contraceptive drugs, such as birth control pills, may decrease the triglyceride-lowering effects of fish oil.

Magnesium supplements may interact with medications such as:

• Bisphosphonates: Magnesium may decrease the absorption of medications in this class of drug used to treat osteoporosis. To prevent the effect, bisphosphonates should be taken two hours before or after magnesium.
• Antibiotics: Certain antibiotics, such as doxycycline and ciprofloxacin, may not be absorbed well if taken at the same time as a magnesium supplement. Antibiotics should be taken two hours before or four to six hours after you take a magnesium supplement. 
• Diuretics: Potassium-sparing diuretics, such as spironolactone (sold under brand names like Aldactone and Carospir), may decrease the amount of magnesium lost through your urine. Especially taken with a magnesium supplement, the diuretic may cause the magnesium level in your body to be too high.
• Zinc: Very high doses of zinc may interfere with your body’s ability to absorb magnesium.

Check with your healthcare provider or pharmacist about any interactions fish oil and magnesium may have with other medications or supplements you are already taking.

What To Look for

When shopping for fish oil and magnesium supplements, it is important you’re buying products that are safe and high-quality. Supplements are not regulated by the FDA the same way medications are. Therefore, shopping for supplements tested by independent third-party organizations helps ensure the ingredients listed are actually the ingredients in the supplement. 

Popular organizations that offer quality testing include United States Pharmacopeia (USP), NSF International, and ConsumerLab.com. You can look for their labels on the product packaging.

Can You Take Too Much Fish Oil or Magnesium?

There is not an official upper recommended limit for fish oil. Taking high doses of fish oil is unlikely to cause adverse health effects. 

Magnesium supplements should not be consumed above the upper recommended limit, unless recommended by a healthcare provider. The daily upper limit for magnesium in dietary supplements and medications in all adults is 350 mg. This limit does not include magnesium naturally found in food. 

Side effects associated with taking too much magnesium include diarrhea, nausea, abdominal pain, irregular heartbeat, and cardiac arrest. The risk for side effects is higher in people with kidney issues. 

There are no known side effects that come from specifically taking fish oil and magnesium together. What you’ll want to do is consider the potential side effects of either supplement alone—which are often minimal. 

Fish oil side effects are usually not serious and do not last long. The most common side effects include:

• An unpleasant taste of fish
• Bad breath
• Burping
• Abdominal pain
• Heartburn
• Nausea
• Diarrhea 
• Rash

Certain forms of magnesium, such as magnesium oxide or magnesium sulfate, may be more likely to cause side effects than others. The most common magnesium supplement side effects include: 

• Nausea and vomiting
• Diarrhea
• Abdominal pain 
• Abdominal cramping 

If you experience gastrointestinal symptoms after taking fish oil and magnesium, you can consider taking the supplements at different times to help relieve symptoms.

Fish oil and magnesium play essential roles in health. If you’re unable to get enough fish oil and magnesium from your diet, your healthcare provider may recommend taking supplements for both.

Taking fish oil and magnesium together may be beneficial to people with certain health conditions, including heart issues. You can talk with your healthcare provider about whether fish oil and magnesium supplements would be beneficial to you.