Vitamins for dogs and cats: which they need, which are over-supplied and when supplementation makes sense
Your dog or cat needs at least 13 vitamins and a dozen minerals to function. Every day. No exceptions. Most come from kibble or diet. But comes from kibble does not always mean arrives in sufficient amounts. Processing, storage and individual needs create a margin that sometimes falls short.
Vitamins for pets is a topic where two extremes coexist: people who think their dog needs nothing because it eats premium kibble, and people who give everything without knowing why. As usual, reality sits somewhere in the middle.
There are situations where a multivitamin makes complete sense. There are others where it is throwing money away. And there are a few where it can even be counterproductive if you pick the wrong product. Let us sort one from the other with data.
In this guide
Which vitamins dogs and cats need (and where it gets tricky)
Dogs and cats share the need for the same vitamin families: fat-soluble (A, D, E, K) and water-soluble (B complex and C). But species differences matter more than they look.
Cats do not convert beta-carotene into vitamin A. They need preformed retinol, which only comes from animal sources. This is not a problem with commercial kibble, but it is with homemade vegetarian or poorly balanced diets. And yes, some owners feed cats vegan diets. Vets see this and it worries us.
Cats are also particularly sensitive to thiamine (vitamin B1) deficiency. Thiamine is heat-labile: it is destroyed by processing heat. Fresh kibble has enough thiamine, but after months of storage in suboptimal conditions, levels drop.
B-complex: the vitamins that run out fastest
B vitamins are water-soluble: they are not stored in the body and need daily replenishment. They are enzymatic cofactors in hundreds of metabolic reactions: energy production (B1, B2, B3, B5), DNA synthesis (B9, B12), neurological function (B1, B6, B12) and red blood cell formation (B9, B12).
They are the first to take a hit when an animal is stressed, recovering, on antibiotics or simply ageing. A senior dog absorbs B vitamins less efficiently than a young adult. And demand rises during metabolic stress: surgery, illness, lactation, fast growth.
Vitamin D3: the one your pet cannot make like you
Humans synthesise vitamin D3 in the skin through sun exposure. Dogs and cats do not do it efficiently, or do not do it at all, depending on the species and studies. They depend entirely on diet. Vitamin D3 is essential for calcium and phosphorus absorption, bone health and immune function.
The catch: it is fat-soluble and accumulates. A vitamin D overdose is one of the most dangerous poisonings in veterinary medicine. It causes hypercalcaemia, soft tissue calcification and kidney failure. That is why doses in a serious veterinary multivitamin are conservative. More is not better.
Zinc, selenium and magnesium: the minerals that get overlooked
Zinc takes part in over 300 enzymatic reactions, including cell division, immune function and skin and coat health. Selenium is a component of glutathione peroxidase, one of the body's main antioxidant systems. Magnesium plays a role in neuromuscular function and energy metabolism.
All three are usually present in kibble, but bioavailability varies hugely with the chemical form. Zinc sulphate absorbs reasonably well. Zinc oxide, worse. Kibble labels rarely specify the chemical form, so it is hard to know how much your pet actually absorbs.
Commercial kibble is formulated to meet FEDIAF (Europe) or AAFCO (US) minimums. These minimums ensure no clinical deficiency, but they do not guarantee optimal nutritional status. It is like saying your car runs on reserve fuel: technically it moves, but it is not ideal for the engine.
Kibble covers the minimums, but minimums are not optimums
There is one argument you hear a lot: if the kibble is complete, no supplement is needed. It is a reasonable argument. But it has caveats.
First: thermal processing of kibble (extrusion at 120 to 150 degrees) degrades heat-labile vitamins. Thiamine, folic acid and vitamin C lose a significant percentage during manufacturing. Manufacturers compensate by adding an initial excess, but the margin tightens with storage time.
Second: kibble fats oxidise over time, especially if the bag is opened and closed repeatedly or stored in warm places. That oxidation consumes vitamin E, which acts as an antioxidant. A kibble bag that has been open in the pantry for 3 months has less vitamin E than the day it was opened.
Third: individual needs vary. A working border collie does not need the same as a couch bulldog. A 15-year-old cat does not absorb like a 3-year-old. A post-surgical dog has metabolic demands that standard kibble does not meet.
Vitamins and minerals table in a vet multivitamin
| Nutrient | Main function | Deficiency risk | Excess risk |
|---|---|---|---|
| Vitamin B1 (thiamine) | Energy metabolism, neurological function | Moderate (heat-labile) | Very low (water-soluble) |
| Vitamin B3 (niacin) | Cellular metabolism, DNA repair | Low in commercial diets | Very low |
| Vitamin B6 (pyridoxine) | Amino acid metabolism, immunity | Low to moderate | Very low |
| Vitamin B9 (folic acid) | DNA synthesis, erythropoiesis | Moderate (heat-labile) | Very low |
| Biotin | Keratin synthesis, fatty acid metabolism | Low to moderate | Very low |
| Vitamin D3 | Ca/P absorption, bone health, immunity | Moderate (not synthesised in skin) | HIGH (fat-soluble, toxic in excess) |
| Vitamin E | Antioxidant, membrane protection | Moderate (consumed by oxidation) | Low |
| Zinc | Immunity, skin, cell division | Moderate (variable bioavailability) | Moderate at very high doses |
| Selenium | Antioxidant (glutathione peroxidase) | Low to moderate | HIGH (narrow safety margin) |
| Magnesium | Neuromuscular function, energy | Low | Low (renal excess is excreted) |
What a good vet multivitamin should (and should not) contain
Not all multivitamins are equal. There are products with 25 ingredients in homeopathic doses that do nothing. And there are products with 8 to 10 well-dosed ingredients that do make a difference. The key is not the number of ingredients but the doses and chemical forms.
Brewer's yeast base. Saccharomyces cerevisiae provides a natural profile of B vitamins, amino acids and beta-glucans. It is a better starting point than a pure synthetic mix because nutrients come in a food matrix that the body recognises and absorbs better.
Full B-complex in meaningful doses. Writing contains vitamin B on the label is not enough. Doses must be high enough to add something on top of what kibble already provides. If thiamine dose is 0.001 mg, it will do nothing.
Fat-soluble vitamins in conservative doses. D3 and E yes, but without overdoing it. You do not want a multivitamin that supplies excessive vitamin D. Here more is not better, and the safety margin is narrower than it looks.
Minerals in bioavailable forms. Zinc sulphate, not zinc oxide. Sodium selenite in controlled doses. Magnesium oxide as a standard and well-tolerated form.
8 signs your pet may need nutritional support
To be clear: these signs do not automatically mean missing vitamins. They can have dozens of causes. But if your pet fits 2 to 3 of these profiles and the vet finds no underlying pathology, a period of multivitamin supplementation makes sense as part of the approach.
Where we have seen the most impact is in senior dogs and cats. From 7 to 8 years on, intestinal absorption capacity drops, antioxidant requirements rise and body vitamin reserves run out faster. It is the profile where supplementation makes the most perceptible difference.
Multivitaminico - 100 gr
Powder multivitamin for dogs and cats with brewer's yeast, full B-complex, vitamins D3 and E, magnesium, zinc and selenium.
If your pet has specific coat or urinary tract issues, a general multivitamin can complement a targeted formulation. Not replace it, but round out the nutritional picture.
Multivitamin Powder - Vittalogy Pets
Brewer's yeast, full B-complex, D3, E, magnesium, zinc and selenium
100g powder - weight-based dosing - dogs and cats
View MultivitaminFrequently asked questions
Can I give my dog human vitamins?
Not advisable. Doses are designed for humans, who weigh and metabolise differently. Some human formulations contain xylitol, which is toxic to dogs. And fat-soluble vitamins (A and D) accumulate: an overdose can be serious. Always use products formulated for pets.
If my dog eats premium kibble, does it need a multivitamin?
Good kibble meets FEDIAF/AAFCO minimums. But thermal processing degrades B and C vitamins. Storage reduces E. And needs vary with age, stress and health. Not all dogs need it, but seniors, convalescents or dogs on homemade diets often benefit.
Which vitamins are toxic in excess for dogs and cats?
Fat-soluble vitamins: A, D, E and K accumulate in fat. D is the most dangerous (hypercalcaemia, kidney failure). Excess A damages the liver. Water-soluble vitamins (B group, C) are safe because the excess leaves through urine. A good multivitamin uses conservative doses of fat-soluble vitamins.
Is brewer's yeast a good vitamin supplement?
Saccharomyces cerevisiae is one of the most complete natural sources of B vitamins, amino acids and beta-glucans. It works well as the base of a multivitamin. Alone it does not cover everything (lacks D3, E, specific minerals), but as the foundation of a complete formulation it makes biochemical sense.
Do cats need the same vitamins as dogs?
Mostly yes, but with critical differences. Cats need preformed vitamin A (they do not convert beta-carotene), do not synthesise taurine or arachidonic acid, and are more sensitive to thiamine deficiency. A product for both species must reflect these differences in the formulation.
From what age does supplementation make sense?
No fixed cutoff. Puppies on growth kibble are usually fine. Healthy adults on a good diet, too. Where it makes most sense: seniors (7+), convalescents, breeds predisposed to deficiencies, and animals on homemade or BARF diets without professional nutritional supervision.
Sources and scientific references
[1] National Research Council. Nutrient Requirements of Dogs and Cats. Washington, DC: National Academies Press; 2006. - DOI
[2] FEDIAF. Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs. 2021. - FEDIAF
[3] Markovich JE, Heinze CR, Freeman LM. Thiamine deficiency in dogs and cats. J Am Vet Med Assoc. 2013;243(5):649-656. - DOI
[4] Stockman J, Fascetti AJ, Kass PH, Larsen JA. Evaluation of recipes of home-prepared maintenance diets for dogs. J Am Vet Med Assoc. 2013;242(11):1500-1505. - DOI
[5] Kritikos G, Parr JM, Verbrugghe A. The Role of Thiamine and Effects of Deficiency in Dogs and Cats. Vet Sci. 2017;4(4):59. - DOI
[6] Zafalon RVA, Risolia LW, et al. Vitamin D metabolism in dogs and cats and its relation to diseases not associated with bone metabolism. J Anim Physiol Anim Nutr. 2020;104(1):322-342. - DOI
[7] Jewell DE, Toll PW, et al. Effect of increasing dietary antioxidants on concentrations of vitamin E and total alkenals in serum of dogs and cats. Vet Ther. 2000;1(4):264-272. - PubMed
[8] Colombini S, Dunstan RW. Zinc-responsive dermatosis in dogs: 41 cases and literature review. Vet Dermatol. 1997;8(3):153-168. - DOI
[9] Todd SE, Thomas DG, Hendriks WH. Selenium balance in the adult cat in relation to intake of dietary sodium selenite and fish-based diets. J Anim Sci. 2012;90(8):2829-2837. - DOI
[10] Fahey GC, Barry KA, Swanson KS. Age-related changes in nutrient utilization by companion animals. Annu Rev Nutr. 2008;28:425-445. - DOI