Pet Supplements Guide: What Actually Works for Dogs & Cats

The pet supplement market is crowded and lightly regulated.

It is full of slick marketing, and much of it plays on the anxiety of people who just want their dogs and cats to stay healthy a bit longer.

That instinct is good. The way most companies exploit it is not.

Supplements can absolutely help your pet get better joints, calmer guts, shinier coats, but only if you stop buying random tubs of "advanced ultra premium" nonsense because the label has a golden retriever looking spiritual on it.

This guide walks through what has evidence behind it, what mostly does not, and how to judge a product before you buy it.

Why Your Pet Might Actually Need Supplements

On paper, "complete and balanced" pet food should cover everything.

For most healthy pets eating a good complete diet, it does. Supplements are for specific needs, not a requirement.

Some pets do have specific needs: stiff joints, itchy skin, a sensitive stomach, or breed-related health problems.

Common reasons supplements help:

• Homemade diets: Home-cooked food usually needs a vitamin and mineral supplement to be complete.
• Specific conditions: Arthritis, allergic skin disease or digestive problems, where a targeted supplement may help alongside veterinary care.
• Genetics: Big dogs with weak joints, flat-faced breeds with breathing problems, cats prone to urinary issues.
• Aging: Older bodies simply do not absorb and use nutrients as efficiently.

Supplements are not magic.

But for the right pet and the right problem, some of them can help, especially when chosen with your vet.

The Four Supplement Types Worth Knowing

Many products on the shelf have little evidence behind them. These four categories are the most widely used, with evidence that ranges from reasonable to limited.

Joint Support: Glucosamine, Chondroitin & Friends

If you share your house with a large dog, an active dog, or any senior animal, joint problems become more likely with age.

Joint supplements exist to slow that train down, not reverse years of damage overnight.

• Glucosamine: Basic building block of cartilage; helps support joint cushioning and fluid.^[1]
• Chondroitin: Often combined with glucosamine to support cartilage.
• MSM: A sulphur compound often added for inflammation, with limited evidence in pets.
• Green-lipped mussel: Naturally rich in omega-3s and joint-supporting compounds.

Note: The cheap soft chews at the supermarket usually contain a sprinkle of these ingredients just to get them onto the label.

Choose products that list exact milligrams for each active ingredient. Keep expectations realistic: a 2022 meta-analysis found no meaningful pain relief from glucosamine and chondroitin products in dogs, so they are supportive care, not pain treatment. A stiff or limping pet needs a vet check.

Best for: Senior dogs, large breeds, active dogs, older cats that hesitate on jumps, and any pet with early signs of stiffness.

RELATED: Check out our 7 Best Dog Joint Supplements article

Omega-3 Fatty Acids: Fish Oil That Isn’t Rancid

Omega-3s are among the most studied supplements for pets.

They have been used for skin, joint, heart and kidney problems (Bauer, 2011), most often for itchy skin and arthritis. They can also have side effects, so ask your vet for a dose.

• Skin & coat: Helps reduce itchiness, dandruff, and dull, flaky skin.
• Inflammation: Can lower overall inflammation, which is tied to arthritis, allergies, and general creakiness.
• Brain & eyes: DHA is part of normal brain and eye development, which is why it is added to many puppy and kitten foods.

Good sources: Salmon oil, sardine oil, anchovy oil, or mixed marine oil with clear EPA/DHA amounts listed per pump or capsule.

Red flags: Bottles that smell like a dock in summer, huge bargain jugs stored unrefrigerated, and foods that brag about "added omegas" without listing actual amounts per serving.

Omega-3s are fragile: heat, air and time damage them. Check the date, store the oil as directed, and throw away oil that smells rancid.

Probiotics & Digestive Support

The gut plays a big role in digestion and immunity.

When the bacteria in there are a mess, you see it in loose stools, gas, itching, or random sensitivity to food.

• Balances gut flora: Supports normal digestion and reduces random episodes of diarrhea or soft stools.
• Immune support: A big chunk of immune cells live in the intestines.
• Better nutrient absorption: A healthier gut means more benefit from every meal.

Decent pet probiotics typically list specific strains and have CFU counts in the billions per dose, not vague "proprietary blends" with no numbers.

Best for: Pets with sensitive stomachs, pets that just finished antibiotics, pets with frequent gas, or those prone to diarrhea from minor food changes.

Multivitamins & General Support Blends

Multivitamins are not as exciting, but they fill in the boring gaps.

They matter mainly when the diet is not complete, such as home-cooked food without a vitamin and mineral mix.

• Vitamins A, B, D, E: Support eyes, nerves, metabolism, and antioxidant defenses.
• Minerals like zinc & selenium: Important for skin, coat, thyroid, and immune function.
• Trace elements: Help with enzyme reactions all over the body.

A complete and balanced commercial food already contains the vitamins and minerals your pet needs, and adding more is not always safe (see the safety section below).

For pets already eating genuinely good food, multivitamins are usually optional rather than essential.

For a deeper look at one of the most popular options, read our guide to fish oil for dogs, including its benefits and risks.

Supplement Comparison Chart

How to Judge Supplement Quality

A fancy label and buzzwords tell you little about what is inside.

If you learn to read the fine print, you can rule out a lot of weak products quickly.

Look for Real Doses

Any brand can list "glucosamine" or "probiotic blend" on the front.

The back of the label is where you find out if that ingredient is doing anything more than decorating the marketing copy.

• Exact milligrams per serving: Serious products list numbers clearly in a supplement facts box.
• No vague "proprietary blends": That usually means tiny amounts of the expensive stuff hidden in a pile of cheap filler.
• Reasonable serving size: If your 20-pound dog supposedly needs 8 chews a day, something went wrong in formulation.

As a rule of thumb, if a supplement looks suspiciously cheap for the claims it makes, the doses are usually too low to be effective.

The NASC Seal and Third-Party Testing

Pet supplements are not pre-approved by the FDA before they hit shelves, which leaves a lot of room for nonsense.

The NASC (National Animal Supplement Council) exists specifically to tighten things up a bit.

• NASC Quality Seal: Indicates the company follows certain manufacturing and quality-control standards.
• Audit requirements: Brands with the seal have passed independent inspections of their processes.
• Label accuracy: The seal suggests the ingredients on the label are more likely to match what’s in the tub.

Is it a perfect guarantee? No.

But between two similar products, picking the one with the NASC seal is usually the less risky bet.

Form Factors: Chews, Powders, Liquids, Pills

Companies love soft chews because they’re easy to sell and easy to overprice.

The form matters less than the dose and your pet’s ability to take it, but each option has quirks.

What Better Brands Have in Common

Before our product picks below, here is a checklist so you can judge other products on your own.

Things better brands tend to have in common:

• Clear dosing information by pet weight, not some vague "1 chew per day" for everything from Chihuahuas to Great Danes.
• Third-party testing or NASC membership mentioned on the website or label.
• Ingredients you can actually recognise instead of endless "proprietary blends."

If a brand seems more focused on colourful packaging and influencer partnerships than hard data, your pet is probably not their real priority.

Matching Supplements to Your Actual Pet

Not every animal needs every supplement, no matter how persuasive the marketing sounds.

Throwing five different powders into the bowl "just in case" is a great way to waste money and potentially unbalance things further.

Dogs that may benefit most:

• Large-breed adults and seniors with visible stiffness or joint history.
• Itchy, allergy-prone dogs that constantly chew paws or scratch.
• Dogs with recurring digestive upsets or sensitive stomachs.

Cats that may benefit most:

• Older cats that jump less or seem hesitant on high surfaces.
• Cats with chronic hairball or gut issues.

You’re not aiming to build a supplement shrine on your kitchen counter.

Pick one problem to address first, joints, skin, digestion, and see if a targeted supplement actually moves the needle over a few weeks.

Safety, Side Effects, and When to Back Off

"Natural" does not automatically mean "safe in any amount."

Too much of the wrong thing can absolutely make your pet worse, not better.

• Fat-soluble vitamins (A, D, E, K): Stored in the body; overdosing repeatedly can become toxic.
• Calcium: Extra calcium for large-breed puppies can actually damage growing joints rather than protect them.
• Human supplements: Some contain Xylitol or other additives that are flat-out dangerous for dogs and cats.
• Medication interactions: Supplements that thin blood or affect the liver can clash with prescription drugs.

The safest approach is: add one new supplement at a time...

If anything goes sideways, stop and reassess instead of doubling the dose because "maybe they just need more."

Top 10 Recommended Supplements (5 for Dogs, 5 for Cats)

Many supplements are overpriced products with a cute label. These are established products with clear labels; for each one we note what the evidence says, which ranges from good to limited.

Talk to your vet before starting any of them. They are split into options for dogs and cats so you don't accidentally give your cat a product meant for dogs.

The 5 Best Supplements for Dogs

• Best Overall Joint Support: Nutramax Cosequin with MSM for Dogs
  It contains glucosamine (FCHG49) and chondroitin (TRH122), Nutramax's own ingredient forms, plus MSM, and Nutramax says Cosequin is the number one vet recommended retail joint supplement brand. Keep expectations realistic: the evidence for glucosamine and chondroitin is mixed (see the 2022 meta-analysis above), so think of it as supportive care alongside your vet's arthritis plan. Our Cosequin vs Dasuquin comparison lists the exact amounts.
• Best Omega-3 Fish Oil: Nordic Naturals Omega-3 Pet
  Fish oil can oxidize (go rancid) when it is old or badly stored, so choose a brand that lists EPA and DHA clearly. This liquid for dogs is pumped onto food, and the brand says its oils are in the triglyceride form. Omega-3s may help some dogs with itchy skin or stiff joints, but they can also cause side effects such as digestive upset (Lenox and Bauer, 2013), so ask your vet for a dose. Warning: it smells like fish.
• Best Probiotic (The Vet Standard): Purina Pro Plan FortiFlora
  It uses one specific probiotic strain, Enterococcus faecium SF68, as a powder you sprinkle on food. The evidence is mixed: in a shelter study, cats given SF68 had fewer episodes of diarrhea, but no difference was found in dogs, where diarrhea was uncommon in both groups (Bybee et al., 2011). It is a reasonable option for mild, short-term digestive upsets; diarrhea that lasts more than a day or two, or comes with vomiting or lethargy, needs a vet visit.
• Best for "Scooting" Issues: Glandex Anal Gland Soft Chews
  If your dog drags their bottom across the carpet, have your vet check the anal glands first, because scooting can also come from infection, allergies or worms. For dogs prone to full glands, Glandex adds fiber, including pumpkin seed, to firm up stools, which the brand says helps the glands empty naturally. The link opens a bundle with wipes.
• Best for Easy Dental Care: ProDen PlaqueOff Powder
  Let's be honest: you probably aren't brushing your dog's teeth every day. This powder is made from a natural seaweed and is added to food. It carries the VOHC Seal of Acceptance for both plaque and tartar (awarded in 2019), which means the company submitted study results that met the Veterinary Oral Health Council standards. It won't replace brushing or a dental cleaning by your vet.

The 5 Best Supplements for Cats

• Best for Gut Health & Immunity: Purina Pro Plan Veterinary Multi Care for Cats
  This powder from Purina combines a prebiotic fiber, live probiotics and an antioxidant, to support digestive and immune health according to the brand. You sprinkle it on food. If your cat stops eating, call your vet first: cats that skip meals can become seriously ill quickly. For mild loose stools, once your vet has ruled out other causes, a probiotic is a reasonable first step.
• Best Joint Support (Cat-Specific): Nutramax Cosequin for Cats
  Use a product made for cats rather than dog chews, which are dosed for dogs. This version comes as soft chews. Older cats who stop jumping on the counter are often in pain, not just "slowing down", so have your vet check for arthritis: prescription pain relief may help more than a supplement.
• Best Hairball Control: Vetoquinol Laxatone
  It’s not glamorous, but if you’re tired of stepping on cold, wet hairballs at 3 AM, buy this. It is a tuna-flavored gel lubricant meant to help swallowed hair pass through the digestive tract. Regular brushing reduces how much hair your cat swallows in the first place, and frequent hairballs, retching or vomiting are worth a vet visit, because they can be a sign of other problems.
• Best Omega-3 for Cats: Nordic Naturals Omega-3 Cat
  An unflavored liquid fish oil made for cats, with 304 mg of omega-3 per mL according to the listing. Omega-3s may help some cats with skin problems or arthritis; ask your vet for the right dose. We no longer list lysine here: it is widely sold for feline herpesvirus (FHV-1), which causes chronic sneezing and runny eyes, but a 2015 systematic review found no evidence that lysine prevents or treats it. If your cat always sounds like they have a cold, ask your vet about the options that are proven to help.
• Best Calming Support: Vetoquinol Zylkene
  Many "calming" products have little evidence behind them. Zylkene contains alpha-casozepine, a compound from milk protein, and a few small studies in cats suggest it may reduce signs of anxiety (for example, a 2017 trial of a diet containing alpha-casozepine and L-tryptophan, de Rivera et al.). Results vary, so use it alongside calm handling and a predictable routine for vet visits, moves or new pets.

How Long Until You See Results?

Supplements are not espresso shots; they work slowly by shifting underlying processes.

If you expect miracles in three days, you will be disappointed and probably bin decent products too early.

• Joint support: Often needs 4–6 weeks of daily use before mobility changes are obvious.
• Skin and coat: Plan on 6–12 weeks, fur has to regrow with better support behind it.
• Probiotics: Digestion may improve within 1–2 weeks if the product suits your pet.
• General multivitamins: Changes are subtle, slightly better energy or resilience over time rather than dramatic moments.

Track before-and-after video of movement, photos of coat condition, or even a short log of symptoms; memory is terrible at noticing slow improvements.

Bottom Line: When Supplements Are Worth Your Money

Supplements are tools, not miracles, and certainly not replacements for proper food, exercise, or real medical care when something is seriously wrong.

Used wisely, though, they can turn "just managing" into "actually doing pretty well" for a lot of dogs and cats.

• Prioritise omega-3s, a solid joint formula, and a good probiotic before you start buying fancy niche blends.
• Choose products with clear doses, honest labels, and preferably the NASC seal.
• Match what you buy to your pet’s real issues instead of chasing every marketing claim.
• Give them long enough to work before you decide they’re useless.

Your pet doesn’t care what the label looks like.

They care whether their hips hurt less, their stomach stops twisting itself into knots, and they can get on the sofa without doing advanced physics first.

If a handful of well-chosen supplements helps them do that, then it’s money well spent, and you’ve successfully dodged a lot of the industry’s nonsense along the way.

Pet Supplements Related Articles

• The No-Nonsense Guide to Healthy Pet Treats (Dogs & Cats)
• Raw Diet for Dogs & Cats: The Complete Beginner's Guide
• Homemade Pet Food Guide: Recipes That Work

References & Scientific Sources

1. Johnston SA. (1997). Osteoarthritis: joint anatomy, physiology, and pathobiology. Veterinary Clinics of North America: Small Animal Practice. 27(4):699–723.
2. Bauer JE. (2011). Therapeutic use of fish oils in companion animals. Journal of the American Veterinary Medical Association. 239(11):1441–1451. doi:10.2460/javma.239.11.1441
3. Bybee SN, Scorza AV, Lappin MR. (2011). Effect of the probiotic Enterococcus faecium SF68 on presence of diarrhea in cats and dogs housed in an animal shelter. J Vet Intern Med. 25(4):856–860. PubMed
4. Lenox CE, Bauer JE. (2013). Potential adverse effects of omega-3 fatty acids in dogs and cats. J Vet Intern Med. 27(2):217–226. PubMed
5. Veterinary Oral Health Council. VOHC Accepted Products. vohc.org
6. NASC (National Animal Supplement Council). Quality Seal Program. nasc.cc
7. National Research Council (NRC). (2006). Nutrient Requirements of Dogs and Cats. National Academies Press.