Fish Oil Benefits and EPA·DHA Content Comparison

Skin & CoatIngredientsMeongsiljang Veterinary Advisory Board

Fish oil is a key ingredient rich in EPA and DHA, two types of omega-3 fatty acids that support skin, joint, and cardiovascular health. Here’s a breakdown of the omega-3 content in different types of fish oil and how to properly administer it.

What is Fish Oil? The Key Source of Omega-3 for Pets

Illustration of a puppy and a kitten sitting next to Eoyu capsules

Fish oil is extracted from oily fish such as salmon, sardines, and anchovies, and is rich in omega-3 fatty acids, specifically EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). The most important factor is the actual EPA and DHA content. Even among products labeled as "fish oil supplements," the EPA and DHA levels can vary by two to three times, so it is essential to check the specific amounts listed on the label. This key ingredient is widely used to support skin, joint, and cardiovascular health in both dogs and cats.

5 Main Benefits of Fish Oil

According to veterinary nutrition textbooks, EPA and DHA from fish oil provide broad benefits for the overall health of dogs and cats.

Skin and Coat Improvement: Supports the skin barrier, reduces inflammatory signals such as itching, and helps promote a shiny, healthy coat.

Joint Inflammation Relief: May help lower pain associated with chronic arthritis and improve mobility.

Cardiovascular Health: Incorporates into cell membranes of heart and blood vessel tissues, competitively inhibiting the production of inflammatory mediators derived from omega-6 fatty acids (arachidonic acid).

Brain and Eye Development: Essential for retinal and neural tissues, supporting neurological and retinal development in young animals.

Kidney Health Management: Used as a supportive measure in managing chronic kidney disease, with specific reference dosages for omega-3 supplementation in renal patients provided in textbooks.

EPA·DHA Key Ingredient Card

Safe

EPA (에이코사펜타엔산)

염증 반응 억제, 관절·피부 가려움 완화

Dosage: 체중 kg당 40mg/일 (일반 건강)

미국수의내과학회(ACVIM) 권장

Safe

DHA (도코사헥사엔산)

뇌·망막·신경 발달, 인지 기능 유지

Dosage: 체중 kg당 25~30mg/일

수의영양학 교과서 기준

Caution

ALA (알파리놀렌산, 식물성)

EPA·DHA로 전환되지만 강아지 전환율 10% 미만, 고양이는 거의 0%

Dosage: 식물성 기름에 주로 존재

Bauer 연구(2011) — 반려동물은 생선 유래 오메가3 권장

Fish Oil Efficacy According to Veterinary Research

Clinical evidence reported in Plumb’s Veterinary Drug Handbook shows that consistent administration of high-dose fish oil rich in EPA and DHA to dogs with arthritis significantly reduces pain indicators and improves quality of life and activity levels. Fish oil is also used as an adjunctive therapy in kidney disease, with veterinary nutrition textbooks providing a specific reference dosage for omega-3 supplementation in renal disease (approximately 140 mg/kg^0.75). In dermatology, multiple studies have confirmed that supplementing dogs with atopic dermatitis with EPA and DHA improves clinical symptoms such as itching. However, the effects of fish oil do not appear immediately. Textbooks recommend consistent administration for about 6 to 8 weeks to properly evaluate the benefits of essential fatty acid supplementation. Therefore, it is important to continue supplementation for an adequate period and then assess the results together with your veterinarian, even if no changes are observed in the short term.

An illustration of a veterinarian examining a puppy, with a bottle of fish oil placed nearby.

Comparison of EPA·DHA Content by Fish Oil Source

Item	Salmon oil	Sardine/anchovy oil	Krill oil	Cod liver oil
EPA content (per 1g)	80–120mg	180–240mg	120–150mg	60–90mg
DHA content (per 1g)	120–180mg	120–180mg	60–90mg	80–120mg
Absorption rate	Moderate	Moderate	High (phospholipid form)	Moderate
Vitamin A/D	False	False	False	True
Recommendation level for pets	Good	Very good	Good	Caution (excess vitamin A)

Average values based on typical commercial ingredients. Variation between products is large.

Recommended Dosage Guidelines by Body Weight

According to the textbook Applied Veterinary Clinical Nutrition, fish oil dosage varies by condition and should be calculated based on metabolic body weight (mg/kg^0.75), not simple body weight (mg/kg). The daily reference doses for combined EPA and DHA are approximately 125 mg/kg^0.75 for general inflammation and atopy, 140 mg/kg^0.75 for kidney disease, 115 mg/kg^0.75 for cardiovascular disease, and 310 mg/kg^0.75 for arthritis. For example, in a 5 kg dog (where kg^0.75 ≈ 3.3), the reference daily dose would be about 410 mg for atopy and about 1,020 mg for arthritis. Because required dosages vary significantly depending on the condition, it is essential to calculate based on the actual EPA and DHA content rather than the total "1,000 mg fish oil" listed on the product label. For safety, please consult your veterinarian to determine the precise dosage.

Proper Fish Oil Administration Methods

Fish oil is best absorbed when given with meals. Since it’s fat-based, it’s better to sprinkle it over kibble or hide the capsule in a treat rather than giving it on an empty stomach.

Storage: Refrigerate after opening and use within 3 months.

Checking for rancidity: If it has a strong fishy odor or a bitter taste, it has oxidized—do not feed it.

Choosing a form: Liquid form allows for easier dosage adjustment, while capsules oxidize more slowly.

Starting dose: Begin with half the recommended amount and gradually increase over 1–2 weeks.

Cats are sensitive to smells, so if you crush the capsule and mix it into their food, they may refuse it. Start with a small amount to test their acceptance.

A dog and a cat standing in front of their bowls, with a single drop of fish oil resting on top of their food.

Side Effects and Precautions of Fish Oil

Fish oil is generally a safe ingredient. According to the BSAVA Manual of Canine and Feline Dermatology, side effects from essential fatty acid (EFA) supplements are minimal and typically limited to intermittent gastrointestinal signs. However, please keep the following points in mind when administering high doses over extended periods.

Gastrointestinal signs: Diarrhea, vomiting, and fishy burps (these are the most common and are the primary side effects noted in the textbook).

Caution with high doses: Cats, in particular, lack a clearly defined safe upper limit for EPA and DHA, so extra caution is warranted when administering high doses for long durations.

Weight management: As a fat-based supplement, fish oil is calorie-dense, so overall dietary balance should be considered.

Products containing Vitamin E: To prevent the oxidation of omega-3 fatty acids, products are commonly formulated with added Vitamin E (d-α-tocopherol).

In most cases, fish oil can be used without issue within the recommended dosage range. However, if your pet is undergoing surgery or has underlying health conditions, please consult your veterinarian before deciding whether to administer it.

Be Sure to Check Before Administering Fish Oil

Please consult your veterinarian before giving this supplement in the following situations: if your pet has a bleeding disorder or is taking anticoagulant medication; if surgery is planned (discontinue use two weeks prior); if there is a history of pancreatitis (due to fat sensitivity); or if your pet is already on a prescription diet containing omega-3s (to avoid the risk of excessive intake). Many prescription diets for kidney, joint, or skin conditions already include EPA and DHA, so adding extra supplements could lead to overdose. For safety, let your veterinarian determine the final dosage based on your pet’s weight and underlying health conditions.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can I give my dog human omega-3 supplements?

While pure fish oil is safe for short-term use, human-grade products may contain additives that are harmful to pets, such as xylitol, artificial fragrances, or excessive vitamin A. Always check the ingredient list carefully, and for safety, it’s best to use products specifically formulated for pets.

When will the effects start to show?

Textbooks generally recommend administering essential fatty acid supplements, such as fish oil, consistently for about **6 to 8 weeks** to properly evaluate their effectiveness. Since it often takes time to see improvements in skin or joint symptoms, please do not stop the supplement if you don't notice changes in the short term. Instead, continue giving it for the full recommended period and then assess the results together with your veterinarian.

Can flaxseed oil be used as a substitute for omega-3?

It’s a bit complicated. Flaxseed oil contains plant-based omega-3 (ALA). According to veterinary textbooks, while both dogs and cats can convert ALA into EPA, their ability to convert it into DHA is limited. In particular, for growing animals or those that are pregnant or nursing, it’s recommended to provide EPA and DHA directly. Therefore, for pets, it’s more effective to supply EPA and DHA directly through fish-derived fish oil.

How should I store the eel oil capsules?

Store in a cool, dark place before opening, and refrigerate after opening. Exposure to light and heat can cause oxidation, leading to the formation of harmful peroxides. If a strong fishy odor develops, discard the product immediately.

Can I give my cat the same dose as my dog?

While the per-kilogram guidelines are similar, cats lack a clearly established safe upper limit for EPA and DHA, so extra caution is warranted with higher doses. We recommend using products specifically formulated for cats or consulting your veterinarian to determine the appropriate dosage.