Flaxseed oil is a supplement that can boost your intake of omega-3 fatty acids. These are considered to help with lowering your cholesterol as well as lowering your chances of developing cardiovascular disease, diabetes, and even some cancers.

Getting omega-3 into your body requires eating it in your diet or consuming it as a supplement, as your body does not produce it on its own.

Flaxseed oil contains a-linolenic acid (ALA), which the body can break down into an omega-3 fatty acid. Flaxseed oil doesn’t have as many benefits as other omega-3 sources like fish, fish oil, and flax in its seed form.

Flaxseed oil is generally cold pressed. You can find flaxseed oil in oil form, in capsules, or even in enriched food products.

You need to take a tablespoon of flaxseed oil to get seven grams of ALA. You may need to take up to six flaxseed oil capsules to achieve this amount in pill form. You can get the same amount of omega-3 fatty acids in your body by consuming fewer fish oil capsules.

Read about how you can use flaxseed oil »

It’s important to be cautious when using flaxseed oil, as there are several risks and side effects. For many, the benefits of flax seeds and flaxseed oil may outweigh the risks of using the product. Use caution when adding flaxseed oil to your diet or using it as a supplement.

Lack of definitive research

There are many studies currently under way to link the use of flaxseed oil with positive health benefits, but there is no standard use of the supplement. Discuss with your doctor the benefits of flaxseed oil for your health before trying it out. You should also discuss the length of time it’s healthy to use it as well as a recommended dosage.

Quality can vary

Flaxseed oil as a dietary supplement is not regulated by the U.S. Food and Drug Administration. Therefore, the quality and contents of flaxseed oil aren’t regulated and standardized. You should use these products with caution.

Low blood sugar

The use of flax seeds or flaxseed oil may result in lowered blood sugar. You need to be careful in using these supplements if you have diabetes or any other condition that affects your blood sugar levels. You should also be cautious about consuming flaxseed oil if you use medications that alter your blood sugar levels.

Low blood pressure

Consuming flaxseed oil may lower your blood pressure. If you have a condition or take a medication that lowers your blood pressure, adding this supplement to your diet could cause complications.


The use of flax seeds may increase your chances of bleeding. This may be problematic if you have a health condition that causes bleeding or if you’re on certain medications that may lead to bleeding, such as blood thinners.

Hormone adjustments

Don’t take flaxseed oil or flax seeds in pregnancy or while breastfeeding. Flaxseed oil may cause complications with women who are pregnant because of its ability to affect hormones.


There is a chance you may have an allergy to flax seeds and flaxseed oil. You should discontinue and avoid the use of flaxseed oil if you notice itching, swelling, redness, or hives when you ingest it. Vomiting and nausea may also be signs of an allergy. See a medical center immediately if your reaction to flaxseed oil causes your throat to tighten or shortness of breath. These might be signs of anaphylactic shock.

Prostate cancer

There is conflicting research about whether ALA found in flax seeds and flaxseed oil actually causes tumors from prostate cancer to be more aggressive. Flaxseed oil does not have the nutrient lignan, which has been linked to slowing tumors for prostate cancer. Additionally, the fat in flaxseed oil may not give your body what it needs if you have prostate cancer. Oncology Nutrition advises that you should discuss the use of flax seeds with your doctor and avoid the use of flaxseed oil altogether because it provides no benefit to those with prostate cancer.

Constipation and diarrhea

Flax seeds are considered to help with constipation. Flaxseed oil doesn’t contain fiber like flax seeds, however. Therefore, using flaxseed oil to relieve your bowels will not have the same effect as using flax seeds. You should consume water regularly if you use flax seeds as a supplement. You may find that flaxseed oil leads to diarrhea.

The side effects of flaxseed oil may lead to adverse reactions if you consume it and take certain medications or have particular medical conditions. Sometimes flax seed will interfere with the absorption of other medications. Often you’ll need to take flaxseed oil a few hours before administering medications to make sure your body absorbs them properly. Additionally, you may have to avoid the supplement completely.

Some medications that may interact with flaxseed oil negatively include:

  • those that alter your blood flow and bleeding, including:
    • aspirin
    • blood thinners, like warfarin (Coumadin) and clopedigrel (Plavix)
    • some nonsteroidal anti-inflammatory drugs, like ibuprofen and naproxen
    • those that regulate blood sugar, including:
      • insulin
      • glipizide (Glucotrol)
      • glucophage (Metformin)
      • glyburide (Micronase or Diabeta)
      • those that alter your estrogen levels
      • those that help with constipation
      • those that lower blood pressure

You should consult your doctor before using flaxseed oil if you have:

Pregnant and nursing women should avoid the use of flaxseed oil.

You should see your doctor immediately if you suspect you’re having a reaction from the intake of flaxseed oil.

To be as proactive as possible, consult your doctor about using flaxseed oil as a dietary supplement before you begin to use it. This will help prevent any negative reactions that might arise.

You may be eager to find a supplement to boost the omega-3 fatty acids in your body. Flaxseed oil may be a good option for you. However, it may cause undesirable side effects if you have a preexisting medical condition, use certain medications, or take the wrong dosage. Consult your doctor before relying on flaxseed oil to boost your omega-3 fatty acid levels to ensure you’re using the supplement safely. Fish oil may be a better and safer choice.