Fish oil tablets contain omega-3 fatty acids that your body uses for brain, heart, and joint function

Fish oil tablets are supplements made from the tissue of fatty fish like salmon, mackerel, and sardines. The main active compounds are two omega-3 fatty acids: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Your body cannot make these on its own, so it relies on food or supplements to get them.

These fatty acids work in your cells to reduce inflammation, support nerve signaling, and help maintain the structure of cell membranes throughout your body. Most research on fish oil has focused on three areas: heart health, brain function, and joint inflammation. The strength of evidence varies for each use, and results depend partly on how much fish oil you take and for how long.

Key Takeaways

  • Fish oil tablets contain EPA and DHA, two omega-3 fatty acids that reduce inflammation and support cell function in your heart, brain, and joints.
  • A typical dose ranges from 1,000 to 3,000 mg per day, though some people take more under medical supervision.
  • Fish oil may help lower triglycerides (a type of blood fat) and support heart rhythm, but it does not prevent heart disease on its own.
  • Side effects are usually mild—fishy aftertaste, nausea, or loose stools—and often improve if you take the tablet with food or switch brands.
  • Fish oil can interact with blood thinners and high-dose aspirin, so tell your doctor if you take either before starting a supplement.

How fish oil affects your heart and blood vessels

Fish oil's most studied effect is on triglycerides, a type of fat in your blood. High triglyceride levels are linked to heart disease risk. Studies show that fish oil at doses of 2,000 to 4,000 mg per day can lower triglycerides by 20 to 50 percent, depending on how high they were to begin with. This effect is strongest in people whose triglycerides are already elevated.

Fish oil may also help maintain a steady heart rhythm and reduce inflammation in blood vessels. However, research does not show that fish oil prevents heart attacks or strokes in people without existing heart disease. If you have heart disease or high triglycerides, your doctor may recommend fish oil as part of a broader treatment plan that includes diet and exercise changes.

What fish oil does for your brain and nervous system

DHA makes up a large portion of the fatty tissue in your brain, so some researchers have studied whether fish oil supplements support memory, focus, and mood. The evidence is mixed. Some studies suggest fish oil may help with mild cognitive decline in older adults, while others show no clear benefit for healthy people.

Fish oil has also been studied for depression and anxiety, with some research pointing to modest improvements in mood when combined with other treatments. The doses used in these studies were typically 1,000 to 2,000 mg per day over several weeks or months. If you are considering fish oil for mental health, discuss it with your doctor first, as it works best alongside other treatments rather than as a replacement.

Fish oil and joint inflammation

People with rheumatoid arthritis have reported less joint pain and swelling when taking fish oil supplements, particularly at doses above 2,000 mg per day. The omega-3 fatty acids in fish oil reduce the production of inflammatory molecules in your body, which may ease joint discomfort over time.

This effect typically takes 8 to 12 weeks to become noticeable, so fish oil is not a quick fix for joint pain. It works best as a long-term supplement, often combined with other treatments your doctor recommends. For general joint health in people without arthritis, the evidence is weaker.

Common side effects and how to manage them

The most frequent side effect is a fishy aftertaste or burp that lingers after taking the tablet. This happens because the fish oil is absorbed in your stomach and released as you digest it. Taking the tablet with food, especially a meal with fat, slows digestion and reduces this effect. Some people find that freezing the tablet before swallowing it helps, since a frozen tablet dissolves more slowly.

Nausea and loose stools occur in some people, particularly at higher doses. Starting with a lower dose and increasing gradually over a week or two gives your digestive system time to adjust. If side effects persist, switching to a different brand or form—such as a liquid or a capsule with an enteric coating designed to dissolve in your intestines rather than your stomach—may help.

Interactions with medications and when to tell your doctor

Fish oil can thin your blood slightly, which matters if you take blood thinners like warfarin or apixaban, or high-dose aspirin. The combination increases your bleeding risk, so your doctor may need to monitor you more closely or adjust your dose. Even if you do not take these medications, mention fish oil to your doctor before starting it, especially if you have a bleeding disorder or are scheduled for surgery.

Fish oil does not interact significantly with most other supplements or medications, but your doctor should know everything you are taking. This is particularly important if you have diabetes, since fish oil may affect blood sugar levels slightly in some people.

How much fish oil to take and what to look for

A typical dose ranges from 1,000 to 3,000 mg per day, though the right amount depends on why you are taking it and your individual health. For general heart health, 1,000 to 2,000 mg per day is common. For high triglycerides, doctors often recommend 2,000 to 4,000 mg per day. Always follow the label instructions or your doctor's recommendation rather than guessing.

When choosing a brand, look for a third-party test seal from organizations like NSF International or USP (United States Pharmacopeia). These seals mean the product has been tested for purity and potency. Check the label for the amount of EPA and DHA listed separately—these are the active compounds, not the total fish oil weight. A tablet labeled "1,000 mg fish oil" might contain only 300 mg of combined EPA and DHA, so read carefully.

Frequently Asked Questions

Can I get enough omega-3s from eating fish instead of taking supplements?

Yes. Eating fatty fish like salmon, mackerel, or sardines two to three times per week provides enough EPA and DHA for most people. Fish also contains other nutrients supplements do not. Supplements are useful if you do not eat fish, are vegetarian, or have a condition like high triglycerides that requires a larger dose than food alone provides.

How long does it take for fish oil to work?

For triglycerides, you may see changes in 4 to 8 weeks. For joint pain or mood, it often takes 8 to 12 weeks. Brain function changes are harder to measure and may take longer. Consistency matters—taking fish oil sporadically will not produce the same results as taking it daily.

Is fish oil safe to take long-term?

Fish oil is generally safe for long-term use at standard doses (up to 3,000 mg per day). Very high doses above 3,000 mg daily may increase bleeding risk or affect immune function, so stay within recommended ranges. Your doctor can advise on safe long-term use based on your health.

What is the difference between fish oil and krill oil?

Krill oil comes from tiny shrimp-like creatures and contains EPA and DHA like fish oil, but in smaller amounts per dose. Krill oil is more expensive and has less research behind it. For most people, fish oil is the more practical choice. Both work similarly in your body.

Can I take fish oil if I am pregnant or breastfeeding?

Fish oil is often recommended during pregnancy and breastfeeding because DHA supports fetal brain development. However, doses and safety vary, so talk to your doctor or midwife before starting. They can recommend the right amount based on your diet and health.