For many people, the decision between fish oil vs krill oil begins with a simple aim: increasing their intake of omega-3 fats. Yet the most suitable option is not always the one with the most elegant packaging or the highest price point. The meaningful differences lie in the amount of EPA and DHA supplied, the form in which they are delivered, and how well the supplement fits your diet, health needs and daily routine.
Both can be valuable sources of long-chain omega-3 fatty acids. The right choice is usually less about finding a universal winner and more about selecting a carefully made product with a dose that suits your needs. Our guide to choosing an omega-3 supplement covers the fundamentals that apply either way.
Why EPA and DHA matter
Omega-3 fats are a family of essential dietary fats. The two most discussed in fish and krill-derived supplements are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). At a daily intake of 250 mg, EPA and DHA contribute to the normal function of the heart, while DHA also contributes to the maintenance of normal brain function and normal vision.
Our bodies can convert only small amounts of EPA and DHA from plant-based alpha-linolenic acid (ALA), found in foods such as flaxseed and walnuts - our explainer on EPA, DHA and ALA sets out how the three differ. This is why oily fish, seafood remains the preferred dietary sources of EPA and DHA, while supplements may be appropriate for people who do not regularly consume these foods. A balanced diet remains the foundation. For adults who eat fish, the usual public health advice is to include two portions each week, one of which is oily fish.
Supplements can offer a practical alternative or complement, particularly for people who avoid fish, dislike its flavour, have an inconsistent diet or are seeking a more targeted intake. Current evidence does not support omega-3 supplements for everyone solely to prevent cardiovascular disease, and they should not replace a healthy lifestyle or prescribed treatment.
Fish oil vs krill oil: the key differences
Fish oil is generally extracted typically from the flesh (body) of oily fish such as anchovies, sardines or mackerel. It is widely available and often provides a substantial amount of EPA and DHA in each serving. Products may contain omega-3s in natural triglyceride form, re-esterified triglyceride form or ethyl ester form. These technical distinctions can influence formulation and cost, but the stated EPA and DHA quantity is usually the most useful comparison point for shoppers.
Krill oil is derived from Antarctic krill, a tiny crustacean. Its EPA and DHA are largely attached to phospholipids, which are fat molecules that are also naturally present in cell membranes. Krill oil also contains astaxanthin, a naturally occurring carotenoid that gives it its characteristic red-orange hue.
The phospholipid form is often presented as a reason to choose krill oil. Some studies suggest omega-3s from krill oil are absorbed more efficiently, but current evidence has not consistently shown clinically meaningful advantages over well-formulated fish oil supplements providing equivalent amounts of EPA and DHA. Overall intake, consistency and the quality of the product remain more decisive than a single ingredient story.
Omega-3 content per serving
This is the practical point that deserves the closest attention. Fish oil often delivers a higher combined quantity of EPA and DHA per capsule or daily serving than krill oil. That can make it more convenient where a higher omega-3 intake is desired, as fewer capsules may be required. The amount of EPA and DHA—not the total amount of oil—is the most important figure when comparing products.
Krill oil products are often sold in smaller capsules but typically provide less EPA and DHA per serving than concentrated fish oil products. A label stating 1,000 mg of krill oil does not mean it contains 1,000 mg of omega-3. The same principle applies to fish oil. Look beyond the headline oil quantity and find the separate amounts of EPA and DHA in the nutritional information.
For example, two supplements may both state that they contain 1,000 mg of oil, while one supplies 600 mg of EPA and DHA and the other supplies 200 mg. Their usefulness cannot be judged from the front-of-pack oil figure alone.
Absorption and tolerance
Taking an omega-3 supplement with a meal that contains some fat can support absorption, whichever source you choose. Some people find krill oil easier to tolerate, reporting fewer fishy aftertastes or repeat sensations. This is individual rather than guaranteed, and a high-quality fish oil capsule, particularly one taken with food, may be equally comfortable.
If fishy burps are a concern, consider the capsule format, serving size and timing. Splitting the dose between meals may help. Enteric-coated products are another option, although they are not necessary for everyone, and there is limited evidence that they consistently reduce gastrointestinal side effects.
Price and everyday practicality
Fish oil is usually the more economical route to a meaningful EPA and DHA dose. It has a long history of use, a broad choice of formats and a range of strengths, from straightforward daily capsules to concentrated formulas.
Krill oil typically costs more per milligram of EPA and DHA. For some, the smaller capsule size, phospholipid format and inclusion of astaxanthin may justify that premium. For others, especially those comparing value or taking a higher daily dose, fish oil may be the more practical choice.
How to choose an omega-3 supplement well
Once you've decided between fish oil and krill oil, the next step is choosing a good-quality supplement. The label should make your decision easier, not more complicated. Begin by identifying how much EPA and DHA the daily serving provides. A supplement's total fish oil or krill oil content is secondary to this figure.
Then consider the source and standard of manufacture. Reputable brands should provide clear information on ingredients, daily dosage and any relevant purity or quality testing. Fish oil should be appropriately purified, and both fish and krill oils should be protected from oxidation. A noticeably rancid smell or taste or if they are past their expiry date is a reason not to continue using a product.
If sustainability is important to you, it's also worth considering how the omega-3 has been sourced. Look for transparent sourcing and independently recognised responsible fisheries standards where available. Choosing products manufactured to recognised quality standards and independently tested for contaminants such as heavy metals and oxidation can provide additional reassurance. Small pelagic fish used for many fish oils can be a resource-efficient source of omega-3, while krill harvesting requires particularly careful management because krill play a central role in the Antarctic food web. There is no single environmental verdict that applies to every product, so traceability matters.
Your preferred format is also relevant. Capsules are simple and portable, while liquid fish oil can suit those who prefer to avoid swallowing several capsules. Flavoured liquids may be easier to take, although they should be stored exactly as directed once opened.
Who may prefer fish oil?
Fish oil is often a sensible choice for someone looking for a flexible, cost-conscious way to increase EPA and DHA intake. It can be particularly suitable when you want a concentrated formula, prefer a liquid option or wish to achieve a higher intake without taking multiple capsules.
It is also the more established category, with a very broad selection of formulations. That makes it easier to match the product to your routine, whether you value a small daily capsule, a high-strength serving or a formula designed to be taken with meals.
Who may prefer krill oil?
Krill oil may appeal if you favour a phospholipid-based source of omega-3 and want a smaller capsule with naturally occurring astaxanthin. It can be an attractive option for those who have found conventional fish oil difficult to tolerate, though it is still worth checking the EPA and DHA amount before assuming it meets your intended intake.
Its premium positioning should be weighed against its dose. Krill oil can be an excellent fit for a modest daily omega-3 supplement, but it may be less efficient for someone specifically seeking a larger amount of EPA and DHA.
Important safety considerations
Fish oil and krill oil are not suitable for everyone. People with a fish allergy should avoid fish oil unless advised otherwise by a healthcare professional. Krill is a crustacean, and so krill oil is not appropriate for people with a crustacean shellfish allergy.
Omega-3 supplements are generally considered safe at typical supplemental doses, but higher doses may increase bleeding risk in some individuals. If you take anticoagulant (such as warfarin or DOACs) or antiplatelet (such as clopidogrel) medicines, have a bleeding disorder, are preparing for surgery, or are pregnant or breastfeeding, speak to a pharmacist, GP or midwife before starting an omega-3 supplement. This is especially important with higher-dose products. Do not use a supplement as a substitute for prescribed treatment or a varied diet.
For tailored support, a pharmacist can help you compare the actual EPA and DHA content of your shortlisted products, consider possible interactions and select a format you will be happy to take consistently. Our omegas and oils range covers both sources. In a category full of impressive claims, a measured approach is often the best investment in your wellbeing.
Pregnant women should avoid supplements made from fish liver oils because these may contain excessive vitamin A.