Best Fish Oil for Dogs with Arthritis

Short answer: the best fish oil for a dog with arthritis is one that clearly lists EPA and DHA per serving, is fresh and well protected from oxidation, comes from a brand with visible quality controls, and arrives in a format your dog will take every day. The brand name matters less than those details. Your vet should set the target amount of EPA and DHA; your job is to find a product that reaches it cleanly.

Marine omega-3s have the strongest evidence of any common joint supplement in dogs, which is why fish oil is usually the first supplement worth discussing. Our joint supplements and nutrition hub explains where it fits alongside weight control, pain relief and other ingredients.

How we chose

We do not test products ourselves. Our picks are based on published veterinary research summarized in plain terms, manufacturer specifications and label details, and patterns in owner feedback. For fish oil, that came down to:

• EPA and DHA listed separately per serving, not just “fish oil” or “total omega-3.”
• A named fish source and, ideally, country of origin.
• Freshness protection: an antioxidant such as vitamin E (mixed tocopherols), a lot number and an expiry date.
• Evidence of quality control: a NASC Quality Seal, published test results, or a clear description of purity testing. The NASC seal is a quality audit, not proof that a product works.
• Formats for every size of dog: liquids and pumps for large dogs, soft gels for small dogs.

Vet note: Ask your vet before starting fish oil, and ask for a target amount of combined EPA and DHA for your dog. This matters most if your dog takes NSAIDs, steroids or blood thinners, has a history of pancreatitis, is on a fat-restricted diet, or has diabetes, kidney disease or liver disease. Never give more than your vet recommends.

What matters when choosing fish oil

EPA and DHA per serving, not “fish oil mg”

The big number on the front of a bottle is often the total amount of fish oil or total omega-3s. That is not the useful figure. A capsule of “fish oil” can contain only a modest share of EPA and DHA, with the rest made up of other fats.

Turn the bottle over and find EPA and DHA listed separately, per pump, per teaspoon or per capsule. Add them together, then work out how many servings your dog needs to reach your vet’s target. Two products that look similar on the front can differ widely on this figure, which also makes it the fairest way to compare value.

Triglyceride vs. ethyl ester

Fish oil comes in a few chemical forms. Natural fish oil is in triglyceride form. Concentrated oils are often converted to ethyl esters, and some are converted back into what labels call re-esterified triglycerides.

Some research, mostly in people, suggests triglyceride forms may be absorbed somewhat better, especially when given without much food. Differences are smaller when the oil is given with a meal, and dog-specific evidence is limited. Treat form as a minor tiebreaker: the EPA and DHA amount and freshness matter more. Many pet fish oils are unconcentrated triglyceride oils, and some brands state the form on the label.

Freshness and oxidation

Fish oil is fragile. Air, heat and light make it oxidize, and oxidized oil is less pleasant, may upset the stomach, and may be less useful. Look for:

• An added antioxidant such as vitamin E or mixed tocopherols.
• Opaque or dark bottles, or individually sealed soft gels.
• A clear expiry date and storage instructions; some liquids need refrigeration after opening.
• A bottle size you will finish well before that date.

At home, smell the oil. Fresh fish oil smells mildly fishy. A sharp or paint-like smell means it has oxidized and should be thrown out.

Purity and third-party testing

Fish can carry environmental contaminants, so reputable brands test their oils for purity and freshness. Small fish such as anchovies and sardines are low on the food chain, which is one reason many oils use them. Some brands publish certificates of analysis or take part in independent testing programs. If a brand gives no information at all about testing, that is a reason to keep looking. Our joint supplement label checklist lists the other label lines worth checking.

Liquid, pump or capsule

Format	Best for	Watch out for
Liquid with measuring spoon or dropper	Medium and large dogs; precise, adjustable amounts	Exposed to air once opened; may need refrigeration
Pump bottle	Large dogs, multi-dog homes, quick daily use	Pump volume and EPA/DHA per pump vary by brand
Soft gels	Small dogs; mess-free, protected from air	Large dogs may need many capsules a day

If your dog is fussy about any supplement, our guide to liquid vs. powder vs. soft chew supplements has tips for hiding and introducing them.

Look-alikes that are not the same

• Cod liver oil. It is made from fish livers and contains vitamins A and D, which can build up to harmful levels with regular use, especially if your dog’s food or other supplements also contain them. Do not use it as a joint supplement unless your vet specifically recommends it.
• Krill oil. A marine source of EPA and DHA in a different chemical form. It usually supplies less EPA and DHA per serving and has thinner dog-specific evidence.
• Algae oil. A fish-free source of DHA, and in some products EPA. Useful for dogs that cannot have fish, with vet guidance.
• Hemp seed, flaxseed and “omega 3-6-9” blends. Plant oils supply ALA, which dogs convert to EPA and DHA only poorly. Our fish oil vs. hemp seed oil comparison explains why they are not joint supplements.
• Combination joint chews with “fish oil.” These usually contain far less EPA and DHA than a dedicated fish oil serving. Count them, but do not rely on them to hit your vet’s target.

The picks

Nordic Naturals Omega-3 Pet (liquid) — best for medium and large dogs

Nordic Naturals Omega-3 Pet is made from anchovy and sardine oil and lists EPA and DHA per serving. The brand describes it as being in triglyceride form; confirm on the current label.

Who it suits: medium and large dogs, and owners who want to fine-tune the amount with their vet.

Strengths: clear labeling, an easy-to-measure liquid, and a brand widely known for fish oil.

Trade-offs: once opened, the bottle is exposed to air, so follow the storage directions and do not buy more than you will use in time. Pouring oil is messier than giving a capsule.

Nordic Naturals Omega-3 Pet Soft Gels — best for small dogs

The soft gel version gives a measured serving in a sealed capsule. For small dogs, a capsule can be given whole in food or punctured and squeezed over a meal, as the label directs.

Who it suits: small dogs, owners who dislike measuring oil, and households that go through fish oil slowly.

Strengths: each capsule stays sealed until used, which helps freshness.

Trade-offs: large dogs may need several capsules a day to reach a vet’s target, which makes a liquid more practical for them.

Nutramax Welactin — best vet-familiar option

Nutramax Welactin is a fish oil from wild-caught cold-water fish, sold as soft gels and as a liquid with a scoop. It is marketed mainly for skin and coat, but it supplies EPA and DHA like other fish oils.

Who it suits: owners whose vet already recommends Nutramax products, or who want soft gels from a vet-familiar brand.

Strengths: EPA and DHA stated per capsule, and a brand most vets know, which makes dosing conversations easy.

Trade-offs: the skin-and-coat labeling does not change what is in the oil, but serving directions on the label may differ from your vet’s joint target. Follow your vet’s amount.

Grizzly Salmon Oil — best pump bottle for big dogs

Grizzly Salmon Oil comes in a pump bottle that makes daily servings quick, which suits large dogs and multi-dog homes.

Who it suits: large and giant breeds and households giving oil to more than one dog.

Strengths: fast to use, and many dogs enjoy salmon flavor according to owner feedback.

Trade-offs: check the EPA and DHA per pump on the label, because pump volumes vary. Larger bottles stay open longer, so choose a size you will finish before it turns.

Zesty Paws Wild Alaskan Salmon Oil — best widely available pump

Zesty Paws Wild Alaskan Salmon Oil is easy to find and uses a pump top.

Who it suits: owners who want a convenient salmon oil from a familiar pet brand.

Strengths: easy to buy and easy to give.

Trade-offs: as with any pump oil, confirm the EPA and DHA per pump and compare it with your vet’s target, and smell the oil regularly once the bottle is open.

Algae-based omega-3 oil — best fish-free option

An algae-based omega-3 oil is the option for dogs with a fish allergy or fish intolerance. Products vary in how much EPA they contain, so read the label carefully.

Who it suits: dogs that cannot have fish, with your vet’s agreement.

Strengths: marine-type omega-3s without fish.

Trade-offs: fewer products made for dogs, and less dog-specific research than for fish oil.

Side effects and safety

Vet note: At higher amounts, omega-3s can affect platelet function and clotting. Tell your vet about fish oil before any surgery or dental procedure, and if your dog takes blood thinners or other drugs that affect clotting. Stop the oil and call your vet if you see vomiting, ongoing diarrhea, unusual bruising or bleeding, or lethargy.

Other points to keep in mind:

• Digestive upset. Loose stool, vomiting and fishy burps are the most common problems. Starting with a smaller amount and building up over a week or two, always with food, helps most dogs.
• Pancreatitis. Oils add fat. Dogs with a history of pancreatitis need a vet-guided plan.
• Calories. Oil is calorie-dense, and extra weight works against sore joints. Adjust food or treats if needed; our guide to weight management for arthritic dogs explains how, and our list of anti-inflammatory food toppers covers fish and other whole foods that fit alongside a supplement.
• Vitamin E. Long-term omega-3 use can increase the body’s need for vitamin E, which is one reason many oils include it. Ask your vet whether your dog’s diet covers this.
• Doubling up. Joint diets and combination chews may already contain fish oil. Add everything up and share the list with your vet.

Getting the amount right

Do not dose fish oil by teaspoons, pumps or capsule counts alone, because EPA and DHA content varies so much between products. Instead:

1. Ask your vet for a daily target of combined EPA and DHA for your dog.
2. Read the EPA and DHA per serving on the label and add them together.
3. Work out how many servings reach the target, and confirm the plan with your vet.
4. Introduce the oil gradually, with meals.
5. Give it several weeks, and track rising, walking and stairs with our daily mobility tracking checklist.

Mistakes to avoid

• Buying by the front label. Big milligram claims on the front usually refer to total oil, not EPA and DHA.
• Grabbing cod liver oil. The vitamins A and D make it a different product.
• Using human gummies or flavored chewables. Some contain xylitol, which is toxic to dogs. Ask your vet before using any human product.
• Buying the biggest bottle. A bottle that takes months to finish may oxidize first.
• Forgetting it before procedures. Put fish oil on your dog’s medication list.
• Stopping at fish oil. Supplements help most alongside a vet’s pain plan, a lean weight and an easier home. Our roundup of the best joint supplements for senior dogs covers what to consider adding, and a supportive bed from our orthopedic bedding guide helps with morning stiffness.