Research-backed reviews of the top supplements for dogs and cats. Compare glucosamine, probiotics, calming chews, fish oil, and multivitamins with ingredient breakdowns and NASC certification details.
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Glucosamine, chondroitin, and MSM work together to support cartilage health, reduce stiffness, and improve mobility in aging dogs and cats. Especially beneficial for large breeds and senior pets.
Probiotics and prebiotic fibers help maintain a healthy gut microbiome, improve nutrient absorption, reduce gas and bloating, and support immune function. Critical after antibiotic use or diet changes.
L-theanine, melatonin, chamomile, and other natural ingredients help reduce situational stress from thunderstorms, fireworks, travel, and separation. A gentler alternative to prescription anxiety medications.
Even with a high-quality diet, many dogs and cats develop nutritional gaps as they age, recover from illness, or face breed-specific health challenges. Pet supplements fill those gaps by delivering targeted nutrients that commercial pet foods may not provide in therapeutic amounts.
Veterinarians increasingly recommend supplements as part of a comprehensive health plan. Joint supplements are one of the most commonly prescribed non-pharmaceutical interventions for senior dogs, and probiotic use has surged as research reveals the connection between gut health and overall immunity. According to the American Veterinary Medical Association, the pet supplement market has grown significantly as more evidence supports their effectiveness when paired with proper nutrition.
Your pet might benefit from supplements if they experience any of the following:
Before starting any supplement regimen, consult your veterinarian. They can rule out underlying conditions that mimic nutritional deficiencies and recommend the appropriate type and dosage based on your pet's specific health profile. This is especially important if your pet takes prescription medications, as some supplements can interact with drugs like NSAIDs or blood thinners.
The pet supplement market includes hundreds of products across several major categories. Understanding what each type does will help you choose the right option for your pet's needs.
Joint supplements are the most popular category, especially for dogs. The primary active ingredients are glucosamine hydrochloride and chondroitin sulfate, which support cartilage repair and reduce inflammation. Many formulas also include MSM (methylsulfonylmethane) for additional anti-inflammatory benefits and hyaluronic acid to improve joint lubrication. Clinical studies in veterinary medicine have shown that consistent use of glucosamine can slow the progression of osteoarthritis and improve mobility scores in dogs. For a deep dive, read our guide to the best glucosamine supplements for senior dogs.
Probiotics introduce beneficial bacteria into your pet's gastrointestinal tract, helping to balance the microbiome. Common strains used in pet probiotics include Lactobacillus acidophilus, Bifidobacterium animalis, and Enterococcus faecium. These supplements are particularly useful after antibiotic courses, during dietary transitions, or for pets with chronic digestive sensitivity. Some formulas also contain prebiotic fibers like inulin and fructooligosaccharides (FOS) to nourish the beneficial bacteria already present in the gut.
Calming supplements use a combination of natural ingredients to reduce stress without sedation. L-theanine, an amino acid found in green tea, promotes relaxation by increasing alpha brain wave activity. Melatonin regulates sleep-wake cycles and is commonly used for noise phobias. Other popular ingredients include chamomile extract, valerian root, and thiamine (vitamin B1). These products work best for mild to moderate situational anxiety. For severe anxiety disorders, they can complement behavioral training and veterinary-prescribed medications. See our full analysis of whether calming chews actually work for dog anxiety.
Fish oil supplements provide EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), two omega-3 fatty acids with potent anti-inflammatory properties. They support skin and coat health, joint function, cognitive development in puppies, and cardiac health. Wild-caught fish oil from cold-water species like anchovies and sardines is preferred because it contains lower mercury levels than oils derived from larger fish. The therapeutic dose for anti-inflammatory effects is typically higher than what is found in commercial pet foods, making supplementation valuable for pets with inflammatory conditions.
Pet multivitamins provide a broad spectrum of vitamins and minerals to address general nutritional gaps. They are most beneficial for pets on homemade diets, picky eaters, senior animals with reduced nutrient absorption, and pets recovering from illness or surgery. Look for formulas that are tailored to your pet's life stage, as the nutritional requirements for a growing puppy differ significantly from those of a senior dog. Multivitamins should complement, not replace, a balanced commercial diet.
We evaluated dozens of pet supplements across five categories, scoring each on ingredient quality, NASC certification, customer reviews, veterinary endorsements, and value for money. Here is a side-by-side comparison of our top-rated products in each category.
| Supplement | Type | Key Ingredients | Price Range | Best For |
|---|---|---|---|---|
| Nutramax Cosequin DS Plus | Joint | Glucosamine HCl, Chondroitin Sulfate, MSM | $25 - $45/mo | Senior dogs with arthritis |
| Purina Pro Plan FortiFlora | Probiotic | Enterococcus faecium SF68, Vitamins A, C, E | $25 - $35/mo | Digestive issues & immune support |
| Zesty Paws Calming Bites | Calming | Suntheanine (L-Theanine), Chamomile, Valerian Root | $20 - $30/mo | Situational anxiety & stress |
| Nordic Naturals Omega-3 Pet | Fish Oil | EPA, DHA from Wild Anchovies & Sardines | $20 - $40/mo | Skin, coat & joint health |
| VetriScience Canine Plus | Multivitamin | 25+ Nutrients, Omega-3s, Probiotics | $15 - $25/mo | Overall wellness for adult dogs |
Cosequin DS Plus is the most veterinarian-recommended joint supplement in the United States, and for good reason. It combines pharmaceutical-grade glucosamine hydrochloride with chondroitin sulfate sourced from bovine cartilage, plus MSM for additional anti-inflammatory support. The formula has been used in multiple published clinical trials demonstrating improved mobility and reduced lameness scores in dogs with osteoarthritis. It is NASC-certified, manufactured in the USA, and available in both chewable tablet and soft chew forms. The brand also offers formulations specifically designed for small dogs and cats.
FortiFlora is the most widely used veterinary probiotic, prescribed by clinics across the country for its simplicity and effectiveness. It uses a single, well-studied probiotic strain, Enterococcus faecium SF68, at a guaranteed viable concentration. The individual sachets make dosing precise and keep the live cultures protected until use. It is particularly effective for managing acute diarrhea, supporting recovery after antibiotic therapy, and improving stool quality during food transitions. It is also one of the few probiotics with actual clinical trial data in dogs and cats. The product is available in both canine and feline formulations.
Zesty Paws Calming Bites combine several evidence-backed calming ingredients into one flavored soft chew. The formula features Suntheanine, a patented and clinically studied form of L-theanine that promotes relaxation without drowsiness. Supporting ingredients include organic chamomile, valerian root extract, and organic passion flower. Many pet owners report noticeable improvement within 30 to 60 minutes of giving the chew, making it useful for predictable stress events like car rides, vet visits, or fireworks. The soft chew format doubles as a treat, which most dogs accept eagerly. It is NASC-certified and made in the USA.
Nordic Naturals Omega-3 Pet delivers a concentrated dose of EPA and DHA from wild-caught anchovies and sardines. The oil is processed without the use of harsh chemicals, using molecular distillation to ensure purity and remove heavy metals, PCBs, and dioxins. It is certified by Friend of the Sea for sustainable sourcing and carries a Certificate of Analysis verifiable on the Nordic Naturals website. Pet owners consistently report improvements in coat quality, reduced itching, and better joint mobility within 4 to 6 weeks. Available in liquid pump form for easy dosing based on body weight. Also suitable for cats.
VetriScience Canine Plus is a comprehensive daily multivitamin delivering 25 or more essential nutrients in a single soft chew. The formula includes omega-3 fatty acids, probiotics, antioxidants, B vitamins, and minerals tailored for adult dogs. It is especially useful for dogs on homemade or raw diets that may lack certain micronutrients, as well as senior dogs with reduced nutrient absorption. The product is developed by veterinarians, NASC-certified, and manufactured in the USA. The duck-flavored chew is accepted readily by most dogs without needing to be hidden in food.
With hundreds of pet supplements on the market, selecting the right one can feel overwhelming. Use the following criteria to narrow your options and make an informed decision.
The pet supplement industry is not regulated by the FDA in the same way as pharmaceuticals or even human dietary supplements. This means quality can vary dramatically between brands. The National Animal Supplement Council (NASC) fills this gap by providing a voluntary quality certification program specifically for animal health products.
NASC-certified companies must comply with rigorous quality standards that include:
When you see the NASC Quality Seal on a product, it means the manufacturer has invested in quality assurance beyond what is legally required. We strongly recommend prioritizing NASC-certified supplements over non-certified alternatives, especially when products appear similar on the surface. The certification provides a meaningful layer of consumer protection in an otherwise loosely regulated market.
All five of our top-rated supplements in the comparison table above carry NASC certification, which was a key factor in their selection. If your preferred supplement is not NASC-certified, look for other indicators of quality such as third-party testing certificates, veterinary endorsements, and transparent ingredient sourcing. For more guidance on specialized nutrition, see our prescription pet food guide.
Most pet supplements are safe when used as directed and purchased from reputable brands. Look for products with NASC (National Animal Supplement Council) certification, which ensures quality manufacturing standards. Always consult your veterinarian before starting any new supplement, especially if your pet takes medications or has underlying health conditions.
Most glucosamine and chondroitin joint supplements take 4 to 8 weeks of consistent daily use before you notice visible improvements in your dog's mobility and comfort. Some dogs may show improvement sooner, while severe cases may take up to 12 weeks. Consistency is key, so do not skip doses during this initial period.
It is not recommended to give dogs human supplements. Human formulations often contain xylitol, artificial sweeteners, or dosages that are unsafe for pets. Pet-specific supplements are formulated with appropriate dosages, safe inactive ingredients, and flavors that improve palatability for animals. Always choose supplements specifically designed for pets.
Calming supplements containing ingredients like L-theanine, melatonin, and chamomile have shown effectiveness for mild to moderate anxiety in clinical studies. They work best for situational stress such as thunderstorms, fireworks, or car rides. For severe anxiety disorders, supplements alone may not be sufficient and should be combined with behavioral training or veterinary-prescribed medications.
NASC (National Animal Supplement Council) certification is a quality seal for pet supplements. NASC-certified products undergo independent quality audits, adverse event monitoring, and label accuracy verification. This certification ensures the product contains what the label claims and was manufactured under strict quality controls. We recommend prioritizing NASC-certified supplements whenever possible.
Read our in-depth guide comparing the top glucosamine supplements for senior dogs, including dosage recommendations, ingredient analysis, and veterinarian insights.
Read the Full Guide