Prescription Omega-3s vs. Supplements

Omega 3 softgels

Verywell / Anastasia Tretiak

Omega-3s have been shown to improve heart, vascular, and brain health in a number of ways. Given this, many seek to get more of them by eating more foods that are rich in these fatty acids and by using omega-3 supplements, be them over-the-counter (OTC) or prescription versions.

There are differences in fish oil and other omega-3 supplements that should be considered, which, in part, is why Rx versions are not appropriate for everyone. And though omega-3s are beneficial, there are some individuals for which supplementation is not advised.

Why Supplement?

Omega-3 fatty acids are in a group of polyunsaturated fats, or “good” fats, that include eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). They boast a number of health benefits, so ensuring that you get an adequate amount is a worthy goal.

Among the health benefits of omega-3s:

  • Studies of individuals with high triglyceride levels have shown that taking anywhere between 2 and 4 grams (2,000 to 4,000 milligrams) of omega-3s per day may reduce triglyceride levels by up to 50%. High triglycerides are linked with heart health concerns, such as stroke and heart attack.
  • Omega-3s may raise HDL ("good") cholesterol and increase the particle size of LDL ("bad") cholesterol, reducing the potential of atherosclerosis.
  • Consuming omega-3s may have other heart-healthy benefits, such as lowering blood pressure and reducing inflammation, among others.
  • There is also evidence to suggest that omega-3s support brain health by, for example, improving mood and sleep, and slowing cognitive decline.

Omega-3s are found in foods such as certain fatty fish; seeds like flax, chia, and hemp; as well as walnuts, soybeans, kidney beans, and seaweed. However, omega-3s are available in much higher amounts in a variety of OTC supplements and prescription drugs.

Types and Omega-3 Content

Visit a vitamin shop and you'll see a wide variety of omega-3 supplements on the shelf. These may be made from:

  • Fish oil (most common)
  • Other marine animal oils (e.g., krill)
  • Plant sources (e.g., algae)

The source of omega-3s plays into a product's overall omega-3 content and its bioavailability (the ease with with your body is able to use it), among other things. And because OTC supplements aren't subjected to the rigorous testing required of prescription drugs, there could be varying levels of EPA and DHA in each product that don't always match what's stated on the label.

Regardless, prescription drugs are highly purified and contain more omega-3s than OTC supplements.

Prescription omega-3 drugs include:

  • Lovaza (omega-3-acid ethyl esters): Contains both EPA and DHA
  • Vascepa (icosapent ethyl): Contains only EPA, potentially making it better suited for those who have high LDL cholesterol.
  • Side effects: Burping and indigestion; changes in taste

  • Has a generic form

  • Cost (without insurance): $447 for 120 capsules, 1 g each ($38 for generic)

  • Contains EPA and DHA

  • Side effects: Muscle and joint pain; constipation

  • Has a generic form

  • Cost (without insurance): $367 for 120 capsules, 1 g each

  • Only contains EPA

Availability and Efficacy

Omega 3 softgels

Verywell / Anastasia Tretiak

While omega-3 supplements are available for anyone to purchase for a variety of uses, omega-3 prescriptions are usually indicated for use in American adults who have very high triglyceride levels (500 mg/dL or more) along with dietary changes. Your medical practitioner may also write a prescription for other medical conditions that could benefit from omega-3s.

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

Potential Side Effects and Risks

Possible side effects of omega-3 supplements and drugs include:

  • Indigestion, heartburn, or burping
  • Diarrhea or flatulence
  • Increased bleeding

Stomach upset is often due to the high fat content of fish oil and can be mitigated by taking fish oil supplements with a meal and early in the day, rather than on an empty stomach or at dinner or bedtime. Another option is to try other omega-3 supplements that do not contain fish oil.

OTC omega-3 supplements that may contain fish should not be used by those with fish allergies. The Rx omega-3s derived from fish are highly purified, yet the risks are still unclear, so those with fish allergies may want to avoid them and opt for plant-based sources instead.

People who take blood pressure medications or anticoagulants, who have hypotension, or who have an increased risk of bleeding or hemorrhagic stroke should seek medical advice before starting omega-3 supplements.

Safety and Purity

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).

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.

That's why it's very important to do your research and only buy OTC supplements from reputable brands. 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 depends on public reporting.

Prescription drugs, on the other hand, are monitored 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 provide evidence 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 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.

Note: Fish oil is highly susceptible to oxidation (becoming rancid), which can compromise OTC supplements.


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

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 healthcare provider. Even though fish oil supplements are readily available, they can still cause certain side effects and aggravate certain medical conditions.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institutes of Health. Omega-3 fatty acids.

  2. Hilleman DE, Wiggins BS, Bottorff MB. Critical differences between dietary supplement and prescription omega-3 fatty acids: a narrative reviewAdv Ther. 2020;37(2):656-670. doi:10.1007/s12325-019-01211-1

  3. Skulas-Ray AC, Wilson PWF, Harris WS, et al. Omega-3 fatty acids for the management of hypertriglyceridemia: a science advisory from the American Heart AssociationCirculation. 2019;140(12):e673-e691. doi:10.1161/CIR.0000000000000709

  4. Food and Drug Administration. Dietary supplements.

Additional Reading

By Jennifer Moll, PharmD
Jennifer Moll, MS, PharmD, is a pharmacist actively involved in educating patients about the importance of heart disease prevention.