The same name... but two very different approaches

Hyaluronic acid has become a staple in products designed to support joints. It can be found both in injections performed by a veterinarian and in many dietary supplements.

However, these two forms do not have the same mode of action or the same level of evidence.

Injections act directly in the body, while orally administered hyaluronic acid must first pass through the digestive tract. The mechanisms are therefore different, as are the effects that can reasonably be expected.

This is a crucial distinction, often overlooked in marketing narratives.

What is its role in a joint?

Hyaluronic acid is a molecule naturally present in many body tissues.

In the joints, it is one of the main components of synovial fluid, which lubricates joint surfaces, facilitates movement, and helps absorb impacts.

When osteoarthritis develops, the quantity and quality of this hyaluronic acid gradually decrease. The synovial fluid becomes less effective, contributing to the loss of joint comfort.

It is based on this observation that viscosupplementation was developed, which involves injecting hyaluronic acid to improve the properties of synovial fluid.

Injectable and oral: why they are not the same thing

Injectable hyaluronic acid acts directly where it is administered.

When injected into a joint, it immediately improves the properties of the synovial fluid and can also influence the biological environment of the joint. Its mechanism is therefore consistent, direct, and well understood.

With oral administration, the situation is very different.

After ingestion, hyaluronic acid is largely degraded in the digestive tract, particularly by the action of the gut microbiota. Only a small fraction is then absorbed.

The most recent studies suggest that the observed effects stem more from the fragments resulting from this degradation and the biological responses they trigger than from a massive passage of the intact molecule to the joints.

In other words, swallowing hyaluronic acid is not equivalent to "injecting" hyaluronic acid.

The two approaches do not have the same functioning or the same level of evidence.

What the studies actually show

The available data are now significantly more robust for injectable forms.

In arthritic dogs, several studies show clinical improvement after intra-articular injection of hyaluronic acid, particularly in dogs suffering from hip dysplasia.

More recently, a study on an injectable form administered intravenously also reported an improvement in several clinical and biological parameters associated with osteoarthritis.

However, these treatments are carried out in a veterinary setting and should not be compared to a freely available dietary supplement.

Data concerning oral administration are more limited.

The most robust canine study was conducted on dogs that underwent surgery for cranial cruciate ligament rupture. After ten weeks of supplementation, researchers observed an improvement in several biomarkers related to inflammation and synovial fluid.

These results are encouraging.

However, they do not demonstrate with the same level of evidence an improvement in pain, lameness, or joint function comparable to that observed with injections.

This is an important nuance: an interesting biological effect does not automatically mean a major clinical benefit.

Why oral hyaluronic acid is controversial

The main question is simple: how much swallowed hyaluronic acid actually reaches the joints?

Early studies had already shown that a small portion of the molecule could be absorbed after ingestion and found in certain tissues.

More recent work has, however, clarified this phenomenon. They show that the bioavailability of oral hyaluronic acid is low, around 0.2% in some experimental models.

Today, researchers therefore believe that its potential effects rely more on indirect mechanisms, notably involving the gut microbiota and the fragments produced during digestion, than on a significant passage of the intact molecule to the joints.

This difference is essential to understand why a hyaluronic acid capsule cannot be considered equivalent to an injection.

Molecular weight: a detail that is not one

Not all hyaluronic acids are identical.

Their molecular weight, i.e., their size, influences their biological behavior and probably their fate after ingestion.

Studies suggest that this characteristic plays a role in the digestion and bioavailability of the molecule.

However, there is currently no universal threshold that can confirm that a given molecular weight is systematically superior in arthritic dogs.

Yet, this is an argument often used in marketing.

At present, the lack of information on the molecular weight of a supplement is primarily a lack of transparency, but the literature does not yet allow for establishing a clear hierarchy between different formulations.

The main marketing pitfall

The most common confusion is presenting oral hyaluronic acid as a direct alternative to injections.

Scientifically, this comparison does not hold up.

Injections have a direct mechanism of action and a more solid level of clinical evidence in dogs.

Oral hyaluronic acid, on the other hand, shows interesting results, but these are primarily based on a few studies and changes in biomarkers. Evidence of a significant clinical benefit remains limited.

Another point rarely specified: many supplements simply state "hyaluronic acid" without mentioning its molecular weight, origin, or studies conducted with the formulation used.

However, this information is essential to assess the scientific quality of a product.

To date, the most cautious position is therefore as follows:

• injectable hyaluronic acid benefits from a more solid scientific record;

• oral hyaluronic acid is an interesting avenue, but it should be considered as a supplement and not as the equivalent of an injectable treatment.

For which dogs?

Injectable hyaluronic acid is used in dogs with diagnosed osteoarthritis or certain other joint conditions, as part of veterinary care.

Its use is generally integrated into a more comprehensive strategy that may combine weight control, adapted physical activity, rehabilitation, pain relief or anti-inflammatory treatments, and, depending on the case, dietary supplements.

Oral hyaluronic acid can also have its place, particularly in dogs with mild to moderate osteoarthritis or as a complement to existing care.

However, current data do not allow it to be considered a substitute for injections or as a treatment capable, on its own, of controlling established osteoarthritis.

Expectations should therefore remain realistic.

Tolerance and precautions

Available studies report a good tolerance profile for oral hyaluronic acid at the doses used.

Injectable forms also show good tolerance when administered in a veterinary setting, although, like any medical procedure, an intra-articular or intravenous injection involves precautions and potential risks.

Finally, the origin of hyaluronic acid can vary among manufacturers. Some products are obtained by bacterial fermentation, others from animal tissues. This information can be useful in certain contexts, even if allergic reactions remain rare.

Key takeaways

Injectable hyaluronic acid and oral hyaluronic acid share the same name, but they are not in the same league.

Injections currently benefit from a higher level of evidence and a direct mechanism of action, which explains their role in the veterinary management of certain joint conditions.

Oral hyaluronic acid is a newer approach. Early studies are encouraging and suggest potential benefits, but evidence remains limited and primarily concerns biomarkers or specific contexts.

Presenting a hyaluronic acid capsule as equivalent to an injection is therefore scientifically inaccurate.

As often in nutrition and veterinary medicine, just because an ingredient is interesting does not mean it produces the same effects regardless of its route of administration.

Sources 

1. Serra Aguado C.I. et al. (2021). Effects of Oral Hyaluronic Acid Administration in Dogs Following Tibial Tuberosity Advancement Surgery for Cranial Cruciate Ligament Injury.

2. Balogh L. et al. (2008). Absorption, uptake and tissue affinity of high-molecular-weight hyaluronan after oral administration in rats and dogs.

3. Šimek M. et al. (2023). Molecular weight and gut microbiota determine the bioavailability of orally administered hyaluronic acid.

4. Carapeba G.O.L. / Alves J.C. et al. (2016). Intra-Articular Hyaluronic Acid Compared to Traditional Conservative Treatment in Dogs with Osteoarthritis Associated with Hip Dysplasia.

5. Matonohová J. et al. (2025). Novel Insights into Systemic Hyaluronic Acid Therapy in Dogs with Osteoarthritis.