What Not to Take With Fish Oil: 7 Key Interactions
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What Not to Take With Fish Oil: 7 Key Interactions
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Fish oil supplements may interact with blood thinners, NSAIDs, blood pressure medicines, orlistat, ginkgo, high-dose vitamin E, and some contraceptive medicines. The main concerns include changes in blood clotting, lower blood pressure, or reduced absorption. Most combinations are not automatically unsafe, but check with your doctor or pharmacist before taking them together.
Fish oil is one of the most popular omega-3 supplements. It contains fats linked to several potential health benefits, especially for heart health and triglyceride levels.
But taking more supplements does not always mean getting more benefits.
Some medicines and supplements can overlap with the effects of fish oil. This becomes more important with high doses or when several products are taken together.
Here are seven interactions worth knowing.
What Are Omega-3 Fatty Acids?
Before looking at fish oil interactions, it helps to understand what omega-3s actually are.
There are three main types commonly discussed:
- Alpha-linolenic acid (ALA)
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
The NIH identifies alpha-linolenic acid ALA, eicosapentaenoic acid EPA, and docosahexaenoic acid DHA as the three omega-3 fatty acids most often studied.
ALA mainly comes from plant foods. Flaxseed oil, chia seeds, walnuts, soybean oil, and canola oil are common sources.
EPA and DHA are found mainly in fish and seafood. Fatty fish such as salmon, sardines, mackerel, and herring are particularly rich in omega-3 fatty acids.
Fish oil is therefore a concentrated source of omega-3 fatty acids, especially EPA and DHA.
Your body can convert some ALA into EPA and DHA, but that conversion is limited. This is why fish, seafood, fish oil, and algal oil are more direct sources of DHA and EPA.
Learn more from the NIH Office of Dietary Supplements — Omega-3 Fatty Acids.
1. Blood Thinners and Antiplatelet Medicines
This is probably the best-known fish oil interaction.
Omega-3 fatty acids can affect platelet activity and blood clotting. At higher doses, they may increase the time it takes for bleeding to stop.
Medicines that also affect clotting include:
- Warfarin
- Apixaban
- Rivaroxaban
- Heparin
- Clopidogrel
- Aspirin
That does not mean fish oil and blood thinners can never be used together.
NIH notes that research has not consistently shown serious bleeding problems from normal fish oil use. However, people taking medicines that affect clotting should discuss omega-3 supplements with their health care provider.
Watch for:
- Unusual bruising
- Frequent nosebleeds
- Bleeding gums
- Blood in urine or stool
- Bleeding that takes longer than usual to stop
If you take warfarin, your doctor may decide whether additional monitoring is needed.
Read more: NCCIH — Omega-3s and Heart Disease.
2. NSAID Pain Relievers
NSAIDs are common medicines for pain and inflammation.
Examples include:
- Ibuprofen
- Naproxen
- Aspirin at certain doses
NSAIDs can increase the chance of stomach or intestinal bleeding.
Because fish oil can also affect blood clotting, regularly combining the two deserves extra attention.
The risk may be more important if you:
- Take NSAIDs every day
- Use high doses
- Have had a stomach ulcer
- Also take a blood thinner
- Are taking several supplements that affect clotting
Occasionally taking ibuprofen does not automatically mean you will have a dangerous interaction.
Still, if NSAIDs are part of your regular routine, tell your doctor or pharmacist that you also take fish oil.
3. Blood Pressure Medications
Omega-3 fatty acids may modestly lower blood pressure in some people.
This is one reason omega-3s are often discussed in relation to heart health.
However, taking fish oil together with medication that already lowers blood pressure could sometimes make the effect stronger.
Examples include:
- ACE inhibitors
- ARBs
- Beta blockers
- Calcium-channel blockers
- Diuretics
Watch for:
- Dizziness
- Lightheadedness
- Weakness
- Blurred vision
- Feeling faint when standing
This does not mean you need to stop fish oil or your prescription.
Never change blood pressure medication on your own. If your readings or symptoms change after starting a supplement, speak with your healthcare professional.
4. Orlistat (Alli or Xenical)
Orlistat is a weight-loss medicine that reduces how much dietary fat your body absorbs.
Because omega-3 fatty acids are fats, orlistat may also reduce the absorption of fish oil.
The main concern here is not bleeding.
It is that you may absorb less of the EPA and DHA from your supplement.
Mayo Clinic advises separating fish oil and orlistat by about two hours.
If you use Alli or Xenical, ask your pharmacist when to take your fish oil supplements.
5. Certain Contraceptive Medicines
Some contraceptive medicines may change the effect fish oil has on triglyceride levels.
This does not mean the combination is dangerous.
It matters mainly if you are taking fish oil specifically because you are trying to lower high triglycerides.
If triglyceride control is the goal, your doctor can use blood tests to see whether your treatment is working.
Do not assume a supplement is effective simply because you take it every day.
6. Ginkgo and Other Supplements That Affect Clotting
Ginkgo biloba is a popular herbal supplement.
It may also affect blood clotting.
Taking ginkgo together with fish oil may deserve more caution, especially if you also take:
- Aspirin
- Warfarin
- Clopidogrel
- Another anticoagulant
The combination is not automatically unsafe.
The concern is that several products may have overlapping effects.
The simplest rule is:
Tell your doctor about supplements just as you would tell them about prescription medicines.
“Natural” does not mean interaction-free.
7. High-Dose Vitamin E
Vitamin E is an important nutrient.
Most people can get it from foods such as:
- Almonds
- Sunflower seeds
- Vegetable oils
- Spinach
- Broccoli
Food sources are usually not the problem.
The concern is mainly high doses of vitamin E from supplements.
High-dose vitamin E may affect platelet activity. Combining it with fish oil may deserve more attention if you also take aspirin or prescription blood thinners.
Do not automatically add vitamin E simply because you take fish oil.
Check your multivitamin and supplement labels first.
Fish Oil vs. Flaxseed Oil
Fish oil and flaxseed oil are both a source of omega-3s, but they provide different types.
Fish oil mainly provides:
EPA + DHA
Flaxseed oil mainly provides:
ALA
The body can convert alpha-linolenic acid (ALA) into EPA and then DHA, but NIH notes that this conversion is limited. Therefore, flaxseed oil should not be viewed as nutritionally identical to fish oil.
That does not make flaxseed oil unhealthy.
It simply means they are different sources of omega-3 fats.
For people who do not eat fish, flaxseed, chia seeds, walnuts, and plant oils can still be useful parts of a healthy diet.
Fish Oil vs. Cod Liver Oil
They are also not the same product.
Regular fish oil mainly provides EPA and DHA.
Cod liver oil provides:
- EPA
- DHA
- Vitamin A
- Vitamin D
If you already take vitamin A, vitamin D, or a multivitamin, check the label before using cod liver oil.
Too much of some fat-soluble vitamins can be harmful.
This is another reason to read the Supplement Facts panel instead of assuming all omega-3 supplements are the same.
What Are the Health Benefits of Omega-3s?
Research on omega-3s covers many areas, but the evidence is stronger for some benefits than others.
One of the clearest effects of long-chain omega-3s is lowering triglyceride levels. NIH reports that fish oil and other long-chain omega-3 supplements can reduce triglycerides.
Omega-3s are also widely studied for heart health and blood pressure.
However, this does not mean taking an OTC fish oil supplement prevents heart disease in everyone.
For most healthy adults, eating fish as part of an overall healthy diet is a more established recommendation.
The American Heart Association recommends two servings of fish per week, especially fatty fish.
Regularly eating fish and seafood as part of a healthy dietary pattern is associated with cardiovascular benefits and may play a role in reducing the risk of cardiovascular disease.
The Best Food Sources of Omega-3s
Supplements are not the only option.
Fatty fish is an excellent source of omega-3 fatty acids.
Good choices include:
- Salmon
- Sardines
- Mackerel
- Herring
- Trout
- Tuna
These foods provide DHA and EPA directly.
Plant foods can provide ALA.
Good plant sources include:
- Flaxseed
- Flaxseed oil
- Chia seeds
- Walnuts
- Canola oil
- Soybean oil
For example, NIH lists flaxseed oil as one of the richest dietary sources of ALA.
A food-first approach also provides protein, vitamins, minerals, fiber, and other nutrients that a capsule alone cannot provide.
Can High Doses of Fish Oil Cause Problems?
More is not always better.
High doses of omega-3 supplements deserve more caution, especially if you take medications.
Potential concerns can include:
- Changes in bleeding time
- Drug interactions
- Digestive symptoms
- Changes in heart rhythm in certain high-risk people
Some studies using about 4 grams per day of omega-3 fatty acids found a small increase in atrial fibrillation among people with cardiovascular disease or a high risk of it.
People with AFib or another heart rhythm condition should discuss high-dose omega-3 use with their doctor.
Fish Oil Side Effects
Most side effects from omega-3 supplements are mild.
According to NCCIH, possible effects include:
- Fishy or unpleasant taste
- Bad breath
- Heartburn
- Nausea
- Diarrhea
- Headache
Taking fish oil with food may make digestive symptoms easier for some people.
If side effects are persistent or severe, stop guessing and speak with a healthcare professional.
How Much Fish Oil Should You Take?
There is no single dose that is best for everyone.
One common mistake is reading:
“1,000 mg fish oil”
and assuming that means:
“1,000 mg EPA and DHA.”
It usually does not.
NIH notes that a typical 1,000 mg fish oil product may contain around 180 mg EPA and 120 mg DHA, although products vary widely.
When comparing supplements, look for:
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
- Total EPA and DHA per serving
Your appropriate dose depends on why you are taking it.
Higher therapeutic doses used to manage very high triglyceride levels should be taken under medical guidance.
Keep an Eye on Everyday Heart & Wellness Trends
Supplements are only one small part of a heart-healthy routine.
Daily habits such as exercise, sleep, nutrition, and activity also matter.
The PulseMax® 2026 All-in-One Health Smartwatch helps you follow everyday wellness trends including:
- Blood pressure trends
- ECG + PPG heart monitoring
- Heart rate
- Blood oxygen
- Blood glucose trends
- Sleep tracking
- Activity and fitness tracking
Tracking these patterns can make it easier to stay aware of changes in your daily routine while working toward better heart health.
Frequently Asked Questions
What should you not take with fish oil?
Use extra caution with blood thinners, NSAIDs, blood pressure medicines, ginkgo, and high-dose vitamin E. Orlistat may also reduce fish oil absorption. Ask your doctor or pharmacist before combining supplements with regular medicines.
Can fish oil affect blood clotting?
Yes. Omega-3 supplements may increase bleeding time, especially at higher doses. People taking anticoagulants, antiplatelet medicines, or NSAIDs should discuss fish oil with a healthcare provider.
Can fish oil lower blood pressure?
Research suggests EPA and DHA may modestly lower blood pressure in some people. If you already take blood pressure medicine, watch for dizziness or unusually low readings and speak with your doctor before changing treatment.
Are fish oil supplements good for heart health?
Fish oil contains EPA and DHA, which have been studied for several aspects of heart health, including triglycerides and blood pressure. However, the health benefits depend on the person, dose, and reason for taking the supplement.
What is the difference between EPA, DHA, and ALA?
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are mainly found in fish and marine oils. Alpha-linolenic acid (ALA) mainly comes from plant foods such as flaxseed oil, chia seeds, and walnuts.
Is flaxseed oil the same as fish oil?
No. Flaxseed oil mainly provides ALA, while fish oil provides EPA and DHA. The body can convert some ALA into EPA and DHA, but the conversion is limited.
Is fish better than omega-3 supplements?
For many adults, food is a good place to start. The American Heart Association recommends eating two servings of fish per week, especially fatty fish rich in omega-3 fatty acids.
Can fish oil lower triglyceride levels?
Yes. EPA and DHA from fish oil and prescription omega-3 products can lower triglyceride levels, with higher therapeutic doses sometimes used under medical supervision.
What are common fish oil side effects?
Common side effects are usually mild and can include fishy taste, bad breath, heartburn, nausea, diarrhea, and headache.
The Bottom Line
Fish oil supplements can be a useful source of EPA and DHA, but they are not right for everyone.
The seven main combinations to check are:
- Blood thinners and antiplatelet medicines
- NSAIDs
- Blood pressure medicines
- Orlistat
- Certain contraceptive medicines
- Ginkgo and similar supplements
- High-dose vitamin E
Also remember that fish oil is only one source of omega-3s.
Fatty fish provides DHA and EPA, while foods such as walnuts, chia seeds, and flaxseed oil provide alpha-linolenic acid (ALA).
For many people, starting with foods rich in omega-3 fatty acids is a simple way to support a balanced diet and overall heart health.
If you take prescription medicines, have a bleeding condition, have heart rhythm problems, or plan to use high doses of omega-3 supplements, talk with your doctor or pharmacist first.