Glucosamine for Dogs: What Big Dog Owners Need to Know

If you’re raising a Great Dane, Mastiff, or any other gentle giant, you probably already know joint health is one of the biggest concerns for these breeds. Their size and weight put extra pressure on their joints, making them more vulnerable to discomfort, stiffness, and conditions like arthritis as they age.

One of the most commonly recommended supplements for joint health in dogs—especially big ones—is glucosamine. But what exactly is it? How does it work? And how do you know if your dog needs it?

Let’s dig in.

What Is Glucosamine?

Glucosamine is a naturally occurring compound found in the body, particularly in cartilage—the tough, flexible tissue that cushions joints and allows for smooth movement.

In healthy dogs, glucosamine plays a key role in maintaining joint function by supporting the repair of damaged cartilage and reducing inflammation. But as dogs get older—or if they experience trauma or developmental joint issues—their bodies produce less glucosamine. That’s when supplementation can help fill in the gaps.

It’s most often sourced from shellfish, but there are also synthetic and plant-based options available.

Why Glucosamine Matters for Giant Breeds

Giant breeds are built differently—and their joints carry a lot more weight. This makes them more prone to joint degeneration and mobility issues, often at an earlier age than smaller breeds.

Supplementing with glucosamine can:

• Support cartilage regeneration to slow joint breakdown

• Reduce inflammation in the joints

• Improve mobility and flexibility, especially in aging dogs

• Ease stiffness and discomfort from osteoarthritis

• Extend quality of life by helping dogs stay active longer

For breeds like Great Danes, Saint Bernards, and Newfoundlands, proactive joint care can make all the difference in keeping them moving comfortably into their senior years.

When Should You Start Giving Glucosamine?

Most people think joint supplements are only for senior dogs—but that’s a mistake, especially for large and giant breeds. The earlier you start supporting joint health, the better the outcomes tend to be.

You might consider starting glucosamine:

• Around 2–3 years of age in giant breeds, as a preventative

• At the first signs of stiffness, reluctance to jump or climb stairs

• After an injury or surgery, as part of recovery

• In aging dogs, to reduce discomfort and support mobility

Remember, joint damage is often irreversible. The goal is to prevent or slow it—not wait until your dog is clearly hurting.

How Much Glucosamine Does Your Dog Need?

Dosage depends on your dog’s weight. Here's a general guideline, but always check with your veterinarian to tailor it to your dog’s individual needs:

• Dogs under 25 lbs: 250–500 mg per day

• 25–50 lbs: 500 mg

• 50–90 lbs: 1,000 mg

• Over 90 lbs: 1,500 mg

Giant breeds (100+ lbs) need more than the standard commercial doses, which is why it’s so important to use a product specifically designed for large and giant dogs—like our Giant Breed Hip & Joint supplement, which is dosed by weight and potency to match their size.

What to Look for in a Joint Supplement

Not all glucosamine supplements are created equal. For big dogs especially, the right formulation makes a huge difference.

Look for:

• Proper dosing based on your dog’s weight

• Multiple active ingredients, like chondroitin, MSM, and eggshell membrane for multi-targeted support

• Natural flavoring that encourages consistent use

• Manufactured in the USA, in FDA-registered facilities that follow GMPs

• No artificial fillers, colors, or preservatives

At The Big Damn Dog Co., we’ve formulated our supplement specifically for the needs of giant breeds—because generic just doesn’t cut it when your dog weighs 120 pounds or more.

Are There Any Side Effects?

Glucosamine is generally well-tolerated by dogs and has been used for decades in both veterinary and human medicine. That said, like any supplement, it’s important to watch for individual sensitivities—especially when starting something new.

Possible side effects may include:

• Mild gastrointestinal upset – This is the most common issue and may include gas, soft stool, vomiting, or diarrhea, especially if the supplement is given on an empty stomach or in a higher-than-needed dose.

• Increased thirst or urination – Some dogs may drink more water or urinate more frequently while adjusting to the supplement.

• Lethargy or fatigue – Occasionally, dogs may appear more tired than usual during the first few weeks.

• Allergic reactions – Most glucosamine is derived from shellfish (shrimp or crab shells), so dogs with shellfish allergies may react with itchiness, swelling, or more serious symptoms. Plant-based or synthetic versions may be an alternative in these cases.

Who should use caution?

• Dogs with shellfish allergies (ask your vet about alternative sources)

• Dogs with diabetes or insulin sensitivity (glucosamine can affect blood sugar levels)

• Dogs with kidney or liver disease—these dogs may still benefit from glucosamine, but should be closely monitored by a vet

• Dogs on blood-thinning medications, as glucosamine may mildly impact clotting

If your dog experiences side effects, stop the supplement and consult your veterinarian. In many cases, lowering the dose or switching to a different form (chewable, powder, or liquid) can help reduce symptoms.

The good news? Most side effects are rare and mild—and many can be avoided with proper dosing, high-quality ingredients, and giving the supplement with food.

How Long Does It Take to Work?

Glucosamine isn’t an instant fix—it’s a long-game supplement. It can take 4–8 weeks to see noticeable changes, especially in older dogs or those with existing joint damage.

That’s why consistency is key. Giving it every day—ideally with food—allows the active ingredients to build up in your dog’s system and provide lasting benefits over time.

How Long Does Glucosamine Stay in a Dog’s System?

Glucosamine can be detected in a dog’s blood for up to 48 hours.

According to veterinary expert Dr. Huwiler, "The time that glucosamine remains in the body varies greatly, but it is rapidly absorbed, highly distributed, and efficiently excreted, which is why it should be administered daily."

This is another reason why consistency matters. To get the full benefit of glucosamine, it needs to be given every day so your dog maintains steady levels in their system over time.

Glucosamine is one of the most well-researched and widely used joint supplements in veterinary medicine—and for good reason. When used correctly, it can help maintain joint health, ease discomfort, and give your big dog more years of mobility and play.

If you’re raising a giant breed, don’t wait until there’s a problem. Preventative care is one of the best gifts you can give your dog—and yourself.

Because when their joints feel better, their whole world opens up.