Prescription Fish Oil vs. Supplements

What's the Difference?

Omega-3 fatty acids are a group of polyunsaturated fats, or “good” fats, that include eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). Although they are found in foods—such as certain fatty fish and nuts—omega-3s are available in much higher amounts in a variety of over-the-counter (OTC) fish oil supplements, as well as prescription drugs like Lovaza (omega-3-acid ethyl esters) and Vascepa (icosapent ethyl), which were approved by the FDA in 2004 and 2012, respectively. Newer options Epanova (omega-3-carboxylic acids) and Omtryg (omega-3-Acid ethyl esters A) may hit the market in the future—they were approved by the FDA in 2014 but are not yet commercially available.

Studies of individuals with high triglyceride levels have shown that taking anywhere between 2 and 4 grams of omega-3 fats per day may be able to reduce triglyceride levels by up to 50%. Having elevated triglycerides is a precursor to cardiovascular disease and associated conditions like heart attack and stroke.

Other Uses

In addition to lowering triglycerides, omega-3s may raise HDL cholesterol (the "good" cholesterol) and increase the particle size of LDL cholesterol, which is beneficial because smaller LDL particles contribute to the development of atherosclerosis. Consuming omega-3s may have other heart-healthy benefits including preventing irregular heart beat (arrhythmia), lowering heart rate and blood pressure, reducing inflammation, and improving the function of blood vessels.

There is also evidence to suggest that omega-3s support brain health: slowing cognitive decline, aiding recovery from traumatic brain injuries, and abating symptoms of ADHD and psychosis in youngsters, to name a few studied benefits.

If you're considering increasing your omega-3 intake with supplements, it's worth reviewing how OTC fish oil supplements and prescriptions containing omega-3 fatty acids compare.

Omega-3 Content

Prescription and fish oil supplements differ in the amount of omega-3 fatty acids they contain. Prescription medications like Lovaza may contain up to 90% omega-3 fatty acids, whereas over-the-counter fish oil supplements contain roughly between 30% and 50% omega-3 fatty acids, depending on the product.

Availability and Efficacy

While fish oil supplements are available for anyone to purchase (for a variety of intentions), omega-3 prescriptions are usually indicated for use in the 25% of U.S. adults who have elevated triglycerides (200–499 mg/dL) or extremely high triglyceride levels (500 mg/dL or more).

When taken in equivalent amounts, prescription omega-3s and over-the-counter fish oil supplements should lower triglycerides in the same manner.

Safety Considerations

Supplements and prescriptions containing omega-3 fatty acids are not all created equal. They each undergo different monitoring as required by the Food and Drug Administration (FDA).

Fish oil supplements found in your local drugstore, like similar OTC products, are classified as “foods” by the FDA. This means that it is the manufacturer’s responsibility to make sure that these products are safe, free of contaminants, correctly labeled, and made in a clean environment. The only way the FDA will remove a supplement from the market is if there have been numerous health complaints about the product after it has reached store shelves, which obviously depends on public reporting.

Prescription drugs, on the other hand, are monitored a little bit differently. To be approved for use as a prescription medication, drugs containing omega-3 fatty acids must undergo extensive testing before they can be prescribed by healthcare providers and sold in pharmacies. The manufacturers must prove to the FDA that the drug works how it is supposed to, that it is safe, and that it contains all of the ingredients stated on the label. They must also disclose any adverse effects experienced by individuals taking the medication.

Because OTC fish oil doesn't undergo the same rigorous testing as required by the FDA, there could be varying levels of EPA and DHA in each product that don't always match what's stated on the label. Additionally, fish oil is highly susceptible to oxidation, which in laymen's terms means becoming rancid. Because they're not regulated heavily by the FDA, there is no guarantee that OTC fish oil supplements are fresh or free from chemicals like dioxins and heavy metals like mercury, which are prevalent in the tissues of ocean fish. Nevertheless, some research suggests that the amount of potential contaminants in OTC fish oil supplements is far less than in a serving of fish that you would eat.

Prescription omega-3s on the other hand, which are extracted from fish oil, are highly purified to remove isomers, heavy metals, and all other impurities to the level of detection. Because these products are derived from fish, it's not known whether they are safe for people with allergies to fish.


Because fish oil supplements do not have to undergo the extensive testing requirements for prescriptions, they are usually much cheaper.

Lovaza vs. Vascepa

With multiple prescription fish oils on the market, it's helpful to know what sets them apart.


  • Side effects: Burping and indigestion; changes in taste

  • Has a generic form

  • Cost (without insurance): $312 for 120 capsules, 1 g each ($105 for generic)

  • Contains EPA and DHA


  • Side effects: Joint pain

  • No generic form

  • Cost (without insurance): $326 for 120 capsules, 1 g each

  • Only contains EPA

Lovaza contains both EPA and DHA, while Vascepa contains only EPA, potentially making it better suited to those who have high LDL cholesterol (the "bad" cholesterol), as DHA is known to increase LDL cholesterol in the blood.

A Word From Verywell

If you are considering adding omega-3 supplements to your diet, you should consult with your healthcare provider. The FDA currently recommends that you should not take more than 2g of fish oil supplements a day unless it is under the guidance of your doctor. Even though fish oil supplements are readily available, they can still cause certain side effects and aggravate certain medical conditions.

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