Collagen for dogs: types and what research shows

Two products with little in common are sold under the name collagen for dogs. Hydrolysed collagen is given in grams and supplies protein broken into small pieces. Undenatured type II collagen, known as UC-II, is given in milligrams and, according to the most widely cited hypothesis, acts on the immune system. Small trials in dogs with osteoarthritis have found improvements with both. There are few of them, though, at least two were paid for by the companies whose collagen was being tested, and the broadest review, from 2022, found only a weak effect.

What collagen is and the forms it comes in

Collagen is the protein that gives skin, tendons, bone and cartilage their strength. There are several types. Type I is the main one in skin, tendon and bone, and type II is the collagen of joint cartilage. On a jar or a label, the word "collagen" can mean either of the two forms below.

Hydrolysed collagen or collagen peptides

It is made by breaking collagen down with enzymes, heat or changes in acidity until only small fragments of 2 to 9 kDa are left, as a 2023 review from the Catholic University of Valencia explains. The collagen tested in the 2024 German trial came from pigs and was mostly type I. The idea is that some of these peptides are absorbed and reach the tissues. The 2022 osteoarthritis review reports that in rats, collagen taken by mouth had a bioavailability of 58%, a figure the authors regard as good.

Undenatured type II collagen (UC-II)

This form is extracted from chicken breastbone using a gentle process that keeps the protein's original structure, a triple helix of about 300 kDa. Commercial products are dosed at only 40 mg a day, containing 10 mg of active ingredient, because it is not meant as building material for cartilage. The proposed explanation is oral tolerance. In rat studies, these small amounts reach the Peyer's patches in the gut and activate regulatory T cells, which release anti-inflammatory substances when they recognise the type II collagen in the joint. According to the Valencia review, the effect takes 2 to 3 weeks to start and up to 3 months to reach its full extent. That review was partly funded by Vetoquinol, which sells a UC-II product, and the mechanism was described in rats, not in dogs.

Collagen in dogs with arthritis

The overall picture

The systematic review and meta-analysis by Barbeau-Grégoire and colleagues (2022) gathered 11 trials of collagen products in dogs and cats with osteoarthritis: UC-II on its own or mixed with glucosamine and chondroitin, eggshell membrane products and one gelatin product. Together they showed a weak effect on pain, and quality was the main problem: three studies had 5 dogs per group and another had 7 to 10. Several used scales that had not been validated and assessed the dogs only a few times, often just once. The authors conclude that on these data it is not possible to say whether collagen works for osteoarthritis in dogs.

UC-II trials

Gupta and colleagues (2012) split dogs with moderate osteoarthritis into four groups of 7 to 10 animals for 150 days: placebo, 10 mg of UC-II, 2,000 mg of glucosamine with 1,600 mg of chondroitin, or all three. All three treated groups improved on the pain score based on observation. On the force plate, which measures how much weight a dog puts on the leg, only the UC-II-only group improved, though with groups this small a couple of dogs are enough to move the average.

A team at the University of Bari published two larger studies, neither with a placebo. In 2019 they compared 60 dogs over 30 days: half took a daily UC-II tablet and the other half took robenacoxib, an anti-inflammatory. Both groups improved by a similar amount on the mobility questionnaire filled in by owners. This study had no outside funding. In 2022, with 76 dogs, they compared cimicoxib, UC-II, the two together and a control group. All three treated groups scored better than the controls, but the control dogs received nothing, not even a placebo, so owners knew whether their dog was being treated. As the article on glucosamine and chondroitin shows, owners also see improvement when their dog is on a placebo.

In healthy dogs there is one placebo-controlled trial, by Varney and colleagues (2022) and funded by Lonza, the maker of UC-II. It gave 40 Labradors aged 5 to 12 either 40 mg of a UC-II product or a placebo. After two weeks on it, they followed an 11-week programme of two runs a week of 5 to 8 km, finishing with a 16 km run. Before the first run, the UC-II dogs scored better on two questionnaire items (how active the dog was and how stiff it was on getting up), and after exercise they appeared to be in less pain.

Hydrolysed collagen trials

The most recent trial was funded by Gelita, which makes the collagen, and run by Dobenecker and colleagues (2024) in Munich, one of whom works for the company. They divided 41 dogs with osteoarthritis between collagen peptides, omega-3 with vitamin E, and placebo for 12 weeks, and 31 completed the study. Neither owners nor vets knew what each dog was getting, but the allocation was not random: dogs were assigned in order of arrival. They walked on a treadmill fitted with force plates. In the collagen group, the force with which the dogs put weight on the affected leg improved more than in the placebo group. Owners' pain scores, however, did not differ between groups, and the accelerometers recorded no increase in activity.

A 2017 trial fed 42 dogs with osteoarthritis for 3 months on either a food containing curcuminoids (from turmeric), hydrolysed collagen and green tea extract or the same food without that mix, a design that gives the collagen no result of its own. The force plates showed no differences, while pain when the joint was handled went down in the treated group.

Skin, coat and older dogs

We found no trials in dogs that measure what oral collagen does for skin or coat. In people, a 2025 meta-analysis of 23 trials with 1,474 participants found improvements in hydration, elasticity and wrinkles when all studies were taken together. Split by funding, though, the improvements appeared only in the studies paid for by the pharmaceutical industry. The rest showed no effect, and neither did the higher-quality studies.

A 2024 meta-analysis of 35 trials and 3,165 patients with osteoarthritis found a little more for human joints: a small to moderate improvement in pain and function, with no more adverse effects than in the control groups. For older dogs, the only dog evidence is the trials above, nearly all of them in animals already diagnosed with osteoarthritis, and none of them tested collagen as a way to prevent joint wear in older dogs without symptoms.

How much the trials gave

The two forms cannot be compared milligram for milligram: work it out for a 20 kg dog and the studied dose of hydrolysed collagen (about 4.8 g) is hundreds of times higher than that of UC-II (10 mg of active ingredient).

The dose is one to agree with your vet, all the more if your dog already takes anti-inflammatories or other joint products.

Who should avoid it

After 150 days in the 2012 trial, no dog showed changes on examination or in liver and kidney tests, and the other dog trials describe hardly any adverse effects either. In people, the 2024 meta-analysis found no more dropouts and no more adverse effects than in the control groups. Still, talk to the vet before starting if your dog has a food allergy or kidney disease, is pregnant or lactating, or already takes other products. Itching, vomiting or diarrhoea once it is on collagen are reasons to stop and tell the vet.

• UC-II comes from chicken, and hydrolysed collagen from other animals, such as pigs in the German trial. For a dog on an elimination diet, any new animal ingredient can spoil the trial.
• We found no published data in pregnant or lactating bitches.
• Collagen often comes mixed with glucosamine, chondroitin or MSM, and each ingredient has its own precautions.
• Hydrolysed collagen is protein. At the dose used in the German trial, a 20 kg dog would get almost 5 g more a day by our calculation, which matters if your dog eats a kidney diet with restricted protein. The 10 mg in UC-II does not count towards that figure.

Sources

1. A 2022 Systematic Review and Meta-Analysis of Enriched Therapeutic Diets and Nutraceuticals in Canine and Feline Osteoarthritis. International Journal of Molecular Sciences, 2022.
2. Management of Osteoarthritis and Joint Support Using Feed Supplements: A Scoping Review of Undenatured Type II Collagen and Boswellia serrata. Animals, 2023.
3. Comparative therapeutic efficacy and safety of type-II collagen (UC-II), glucosamine and chondroitin in arthritic dogs: pain evaluation by ground force plate. Journal of Animal Physiology and Animal Nutrition, 2012.
4. Evaluation of the Effects of Undenatured Type II Collagen (UC-II) as Compared to Robenacoxib on the Mobility Impairment Induced by Osteoarthritis in Dogs. Veterinary Sciences, 2019.
5. Evaluation of clinical efficacy of undenatured type II collagen supplementation compared to cimicoxib and their association in dogs affected by natural occurring osteoarthritis. Research in Veterinary Science, 2022.
6. Impact of supplemented undenatured type II collagen on pain and mobility in healthy Labrador Retrievers during an exercise regimen. Translational Animal Science, 2022.
7. The oral intake of specific Bioactive Collagen Peptides (BCP) improves gait and quality of life in canine osteoarthritis patients. PLOS ONE, 2024.
8. A randomized, double-blind, prospective, placebo-controlled study of the efficacy of a diet supplemented with curcuminoids extract, hydrolyzed collagen and green tea extract in owner's dogs with osteoarthritis. BMC Veterinary Research, 2017.
9. Effects of Collagen Supplements on Skin Aging: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. The American Journal of Medicine, 2025.
10. Efficacy and safety of collagen derivatives for osteoarthritis: A trial sequential meta-analysis. Osteoarthritis and Cartilage, 2024.