Pet Nutrition

Supplements for Pets: Which Ones Actually Work?

📅 Published December 2025 🕓 7 minute read

Walk into any pet store and you'll find shelves lined with supplements promising everything from shinier coats to improved joint health to better digestion. The pet supplement industry is booming, but does your pet actually need these products? More importantly, do they work?

Unlike prescription medications, supplements aren't strictly regulated, and claims don't always match scientific evidence. Some supplements have solid research supporting their use, while others are expensive placebos that primarily benefit manufacturers' bottom lines. Let's separate science from marketing and identify which supplements actually deliver on their promises.

Supplements with Strong Evidence

Omega-3 Fatty Acids (Fish Oil)

What they are: EPA and DHA, omega-3 fatty acids derived from marine sources like fish oil or algae.

The evidence: This is one of the most well-researched and beneficial pet supplements. Studies demonstrate omega-3s provide multiple health benefits:

• Anti-inflammatory effects: Reduces inflammation associated with arthritis, allergies, and inflammatory bowel disease
• Skin and coat health: Improves coat quality and reduces itching in allergic dogs
• Heart health: Supports cardiac function, particularly beneficial for dogs with heart disease
• Cognitive function: May slow cognitive decline in senior pets
• Kidney disease support: Can help slow progression of chronic kidney disease in cats

Who benefits: Senior pets, pets with arthritis, allergic pets, those with heart or kidney disease, and pets with inflammatory conditions.

Dosing: Varies by condition. Look for products standardized for EPA and DHA content. Typical doses range from 20-50 mg combined EPA/DHA per pound of body weight daily, but consult your veterinarian.

Quality matters: Choose purified fish oil to minimize mercury and other contaminants. Refrigerate after opening and watch expiration dates, as fish oil oxidizes.

Glucosamine and Chondroitin

What they are: Compounds that support cartilage health and joint function.

The evidence: Research shows moderate benefits for osteoarthritis. While not miracle cures, studies demonstrate glucosamine and chondroitin can:

• Reduce joint pain and inflammation
• Improve mobility in some arthritic pets
• Potentially slow cartilage breakdown

Evidence is stronger for dogs than cats, though some cats benefit. Results vary between individuals, with some pets showing significant improvement and others minimal response.

Who benefits: Pets with diagnosed arthritis, senior pets with joint stiffness, large-breed dogs predisposed to hip dysplasia.

Dosing: Typically 20 mg glucosamine per pound body weight daily, with chondroitin usually included at lower doses. Effects take 4-6 weeks to become apparent.

Important note: Many joint supplements combine glucosamine and chondroitin with other ingredients like MSM or green-lipped mussel. Evidence for these additions varies.

Probiotics

What they are: Beneficial bacteria that support digestive and immune health.

The evidence: Growing research supports probiotic use for specific conditions:

• Acute diarrhea: Can shorten duration and severity
• Antibiotic-associated diarrhea: Helps prevent digestive upset when pets take antibiotics
• Inflammatory bowel disease: May reduce symptoms in some pets
• Stress-related digestive issues: Can help stabilize digestion during stressful events

Who benefits: Pets with digestive issues, those taking antibiotics, pets with inflammatory bowel disease, or those experiencing stress-related GI upset.

Quality matters: Not all probiotics are equal. Look for products specifically formulated for pets with multiple bacterial strains, guaranteed live organisms, and proper storage requirements. Species-specific strains (like those from dogs or cats) may be more effective than human probiotics.

Supplements with Moderate Evidence

SAMe (S-Adenosylmethionine)

What it is: A compound that supports liver function and has antioxidant properties.

The evidence: Studies show SAMe can benefit pets with certain liver conditions. It may help protect liver cells and support liver regeneration. Evidence is strongest for specific conditions like chronic hepatitis.

Who might benefit: Pets with diagnosed liver disease, under veterinary guidance.

Important: This should only be used with veterinary supervision for diagnosed conditions, not as a general preventive.

Milk Thistle (Silymarin)

What it is: An herbal supplement with antioxidant and anti-inflammatory properties.

The evidence: Some studies suggest milk thistle may support liver health, though evidence is less robust than for SAMe. It's generally considered safe with few side effects.

Who might benefit: Pets with liver issues, though more as complementary support than primary treatment.

L-Carnitine

What it is: An amino acid involved in fat metabolism.

The evidence: May help with weight loss when combined with calorie restriction and exercise. Some evidence suggests benefits for certain heart conditions in dogs.

Who might benefit: Overweight pets on weight loss programs, certain dogs with heart disease (under veterinary guidance).

Supplements with Limited or Unclear Evidence

CBD Products

Current status: While CBD is hugely popular, research on its effectiveness and safety in pets is limited. Some pet owners report benefits for anxiety and pain, but controlled studies are lacking. Legal status varies, and quality control is inconsistent across products.

The caution: Without regulation and solid research, it's difficult to recommend specific products or doses. If considering CBD, work closely with a veterinarian knowledgeable about these products.

Antioxidants (Vitamins E and C, Beta-Carotene)

The theory: Antioxidants combat free radical damage associated with aging and disease.

The reality: While antioxidants are important nutrients, supplementing beyond what's in quality food hasn't been proven to extend life or prevent disease in healthy pets. They may have specific benefits in certain medical conditions, but blanket supplementation isn't clearly beneficial.

Cranberry

Common claim: Prevents urinary tract infections.

The evidence: Limited and conflicting. While cranberry may prevent bacteria from adhering to bladder walls in humans, evidence in pets is weak. It's not a substitute for treating active infections.

Supplements to Avoid or Use Cautiously

Joint Supplements with Unproven Additives

Many joint supplements include ingredients like MSM, cetyl myristoleate, or boswellia. Evidence for these is limited, though they're generally safe. You may be paying extra for unproven ingredients.

Supplements for Undiagnosed Conditions

Don't supplement for conditions you've self-diagnosed. For example, don't give liver support supplements "just in case" or because you read about it online. Work with your veterinarian to diagnose conditions before treating.

Human Supplements

Some human supplements are safe for pets, but many aren't. Doses differ, and some human formulations contain xylitol or other ingredients toxic to pets. Always use pet-specific products or consult your veterinarian.

Making Smart Supplement Decisions

When to Consider Supplements

• Your pet has a diagnosed condition that may benefit from supplementation
• Your veterinarian recommends them for specific health issues
• Your pet eats a homemade diet (requires supplementation for completeness)
• Your senior pet shows signs of cognitive decline or joint issues

When Supplements Aren't Needed

• Your pet is healthy and eating complete, balanced commercial food
• You're trying to "prevent" undiagnosed or non-existent problems
• Marketing claims sound too good to be true
• The supplement promises to cure multiple unrelated conditions

Choosing Quality Supplements

Supplement regulation is minimal. Protect your pet and your wallet by:

• Looking for NASC seal: The National Animal Supplement Council certifies quality and label accuracy
• Choosing reputable manufacturers: Established companies with veterinary oversight
• Checking for third-party testing: Some companies voluntarily submit to independent testing
• Being wary of extreme claims: If it sounds too good to be true, it probably is
• Asking your vet: They can recommend specific brands they trust

Working with Your Veterinarian

Always discuss supplements with your veterinarian before starting them. They can:

• Determine if your pet actually needs supplementation
• Recommend appropriate products and doses
• Monitor for side effects or interactions with medications
• Assess whether supplements are providing benefits
• Suggest prescription alternatives if needed

Don't hide supplement use from your vet. They need to know everything your pet consumes to provide optimal care and avoid dangerous interactions.

The Bottom Line

Some supplements, particularly omega-3 fatty acids, glucosamine/chondroitin, and probiotics, have solid evidence supporting their use for specific conditions. Others are unproven or unnecessary for healthy pets eating quality food.

Supplements aren't magic pills that replace proper nutrition, exercise, and veterinary care. They're tools to address specific health issues or support pets with particular needs. Used appropriately, they can improve quality of life. Used indiscriminately, they waste money and may even cause harm.

The supplement industry relies on pet owners' love for their animals and willingness to do anything to help them. Don't let emotion override evidence. Base supplement decisions on science, veterinary guidance, and your individual pet's documented needs.

Your money is better spent on quality food, regular veterinary care, appropriate exercise, and mental stimulation than on a cabinet full of unproven supplements. When supplements are truly needed, choose wisely and use them as part of a comprehensive approach to your pet's health.