Vitamin E for dogs: what it does

Vitamin E is an essential nutrient for dogs. It has to come from food, and every complete dog food contains it. Its role as an antioxidant is well established, and dogs are known to need more of it when their diet contains more omega-3 fats. Given as an extra for specific problems, it has little evidence in dogs, and that points both ways: a small trial in atopic dermatitis found a benefit, and a larger one in osteoarthritis did not.

What it is and why dogs need it

The name vitamin E covers several substances, the tocopherols (alpha, beta, gamma and delta). Alpha-tocopherol is the one that matters. The others have much less activity as a vitamin, and gamma has almost none. Vitamin E is fat-soluble, so it is absorbed with the fat in food and stored in fatty tissue and in cell membranes.

That is where it works as an antioxidant. Membranes are full of polyunsaturated fats, which oxidise easily, and vitamin E breaks that chain reaction. According to the Merck Veterinary Manual, the signs of deficiency come mainly from this oxidative damage to membranes. Vitamin C can regenerate it. The same manual notes that vitamin C is added to some pet foods as a natural preservative, to regenerate the tocopherols that stop the fat going rancid.

How much vitamin E does a dog need?

The 2025 FEDIAF nutritional guidelines, the reference used by the European pet food industry, set these minimums for a complete dog food:

FEDIAF sets no maximum for vitamin E in dogs. The US National Research Council (NRC) is a separate body and counts in milligrams: its summary for owners recommends 8 mg a day for an adult dog of about 15 kg eating 1,000 kcal. In the IU that FEDIAF uses, a 20 kg dog eating about 1,000 kcal a day of a complete food gets at least 9 IU from it.

Why a dog on omega-3 needs more

The more polyunsaturated fat there is in the diet, the more vitamin E is used up protecting it. According to FEDIAF, the requirement depends on the amount of polyunsaturated fatty acids and other antioxidants, and may rise when intake is high, especially with fish oil. For cats it specifies an extra 5 to 10 IU for each gram of fish oil per kilo of food. For dogs it gives no figure.

Two studies in dogs show the effect:

• In 20 beagle bitches aged 9.5 to 11.5 years, the diet richer in omega-3 (an omega-6:omega-3 ratio of 1.4:1) left blood vitamin E 20% lower than the diet low in omega-3 (31:1), and increased markers of fat oxidation in blood and urine.
• Among the 27 huskies in a 2026 study, those given the highest dose of EPA+DHA for eight weeks ended up with less vitamin E in their blood than the low group (3.52 against 5.82 µg/ml), although oxidation markers did not rise.

If your dog has omega-3 regularly, the product or the rest of the diet should supply enough vitamin E to match.

When dogs lack it, and when they get extra

Deficiency

On a complete food it is rare, but according to the NRC and the Merck manual, dogs fed diets without vitamin E develop muscle degeneration with weakness, reproductive failure (testicular damage in males; weak or stillborn puppies in females), degeneration of the retina and brown pigmentation of the intestinal muscle.

English cocker spaniels are the one known exception: they can have an inherited retinopathy caused by vitamin E deficiency. Affected dogs build up pigment at the back of the eye and lose vision, and some have trouble with balance and with coordinating the hind legs, always with low blood alpha-tocopherol. In 2025 an associated mutation was identified in the gene for the protein that carries alpha-tocopherol, which makes a DNA test possible.

Skin and atopic dermatitis

Dogs with atopic dermatitis have been found to have lower blood vitamin E. A small 2014 trial took 29 such dogs, all on an antihistamine, and gave 14 of them 8.1 IU of vitamin E per kg of body weight a day for eight weeks and the other 15 a mineral oil placebo. In the vitamin E group, blood vitamin E and antioxidant capacity were higher than in the placebo group, and skin lesions scored lower. The abstract does not report a difference in itching.

A 2025 review of diet and atopic dermatitis rates the evidence for vitamin E as minimal, though it may be useful alongside treatment.

Osteoarthritis

A 2023 double-blind trial with 57 large-breed dogs with osteoarthritis found that 400 IU of vitamin E a day for 90 days did not improve pain, lameness or quality of life compared with placebo, and did not reduce the need for rescue painkillers. The authors note that an earlier study, in dogs whose cruciate ligament had been cut surgically, did find less pain and lameness at the same dose. They put the difference down to the inflammation there being recent, not chronic osteoarthritis. They also admit that the vitamin E group weighed more than the placebo group, and that they did not measure whether blood vitamin E actually went up. On the evidence so far, there is no reason to expect vitamin E on its own to improve a dog with osteoarthritis.

Older dogs and cognition

Vitamins E and C on their own were less effective than other ingredients such as omega-3s in a 2025 systematic review of diets and products for cognitive function in older dogs and cats. They are still needed, though, to keep omega-3s from oxidising.

Natural or synthetic vitamin E

Natural vitamin E is d-alpha-tocopherol (also called RRR-alpha-tocopherol). The synthetic form is dl-alpha-tocopherol (all-rac), which has less activity per milligram. That is why amounts are given in international units (IU), which already correct for the difference. The reference is dl-alpha-tocopheryl acetate, where 1 mg equals 1 IU. This is the FEDIAF conversion table:

So when comparing products, look at the IU, not the milligrams. And when a label lists only "tocopherols" as the product's antioxidant, these may be forms such as gamma that hardly count as vitamin E.

How trial doses compare with a dog's needs

Both trials gave far more than the 9 or 10 IU a day that a complete food must supply a 20 kg dog. Doses that high are for the vet to set.

• Atopic dermatitis: 8.1 IU per kg of body weight a day for eight weeks (about 160 IU for a 20 kg dog).
• Osteoarthritis: 400 IU a day in large-breed dogs for 90 days, with no effect.

Safety

The Merck manual counts it among the least toxic of the fat-soluble vitamins. In the osteoarthritis trial, 400 IU a day for 90 days did not change blood test results. The risk comes with very high doses, which can get in the way of absorbing the other fat-soluble vitamins (A, D and K) to the point of causing signs of deficiency. A shortage of vitamin K lengthens clotting time.

• If your dog has a clotting disorder or takes medication that affects clotting, ask before giving extra vitamin E.
• Do not use vitamin E capsules made for people without asking. One capsule can be a very high dose for a small dog.
• If your dog is an English cocker spaniel and you notice it seeing less well, stumbling or unsteady on its feet, ask for an eye examination and blood tests.
• If your dog takes omega-3 at high doses, check that the vitamin E in its diet keeps pace.

Sources

1. FEDIAF Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs. FEDIAF, 2025.
2. Your Dog's Nutritional Needs: A Science-Based Guide for Pet Owners. National Research Council, 2006.
3. Nutritional Requirements of Small Animals. Merck Veterinary Manual.
4. The ratio of dietary (n-6) to (n-3) fatty acids influences immune system function, eicosanoid metabolism, lipid peroxidation and vitamin E status in aged dogs. Journal of Nutrition, 1997.
5. Revisiting eicosapentaenoic acid and docosahexaenoic acid recommendations for healthy Siberian Huskies at maintenance: greater dietary EPA and DHA increase plasma lipid incorporation and reduce α-tocopherol concentrations. Journal of Animal Science, 2026.
6. A TTPA deletion is associated with retinopathy with vitamin E deficiency in the English Cocker Spaniel dog. G3 Genes, Genomes, Genetics, 2025.
7. Vitamin E supplementation in canine atopic dermatitis: improvement of clinical signs and effects on oxidative stress markers. Veterinary Record, 2014.
8. The Role of Diet, Nutrition, and Supplements in Canine Atopic Dermatitis. Veterinary Clinics of North America: Small Animal Practice, 2025.
9. A blinded, placebo-controlled study on the clinical effects of vitamin E supplementation in dogs with osteoarthritis. Journal of Veterinary Internal Medicine, 2023.
10. Enhancing cognitive functions in aged dogs and cats: a systematic review of enriched diets and nutraceuticals. GeroScience, 2025.