Thiamine, or vitamin B1, plays an important role in feline health, and supplements can help when a vet identifies a need. We compared thiamine and B-vitamin products for cats on potency, format, supporting nutrients, and how transparently they state their dose. Our evaluation relied on manufacturer specs and aggregated owner feedback rather than any clinical testing we can’t substantiate. Thiamine status in cats is genuinely a veterinary matter, so we strongly recommend talking to your veterinarian before supplementing, especially if you suspect a deficiency. A supplement supports a diet and a treatment plan, it does not replace a diagnosis. In this guide we focus on clear potency, palatable formats like drops and chews, and sensible co-nutrients, so you can choose a product that fits your vet’s guidance and that your cat will actually take.