What Is MSM for Dogs? What It Does, Typical Amounts and Safety

Flip a dog joint chew over and somewhere near the glucosamine you'll spot three letters... MSM. So what is MSM for dogs, and is it actually doing something for her hips? Short version: it's a sulfur compound, it's in a lot of joint products, and the dog research is thinner than the label makes it sound. Here's what we found, what nobody knows yet, and what to ask your vet before you add more.

What MSM for dogs actually is

MSM stands for methylsulfonylmethane. Big name, small molecule. It's basically one sulfur atom with some carbon, hydrogen and oxygen hanging off it.^[1]

Plants, animals and people all have a bit of it naturally, and you'll find traces in fruit, veggies, grains and milk.^[1][3] Traces is the right word, we're talking hundredths of a part per million. The MSM that goes into supplements is made commercially, and one way to make it is from DMSO, a related solvent.^[1][2] So if MSM is on the label, somebody added it on purpose. It didn't sneak in with the beef.

What MSM does, and what nobody has shown in dogs yet

Most of what's known comes from lab dishes, lab animals and people. In that research MSM looks like it turns down some of the signals the body uses to drive inflammation, and it behaves a little like an antioxidant.^[1] That's why formulators like to pair it with glucosamine and chondroitin.

In one human trial, 49 adults with knee arthritis took MSM or a placebo for 12 weeks. Pain went down a little in the MSM group & daily function went up a little. The authors were pretty upfront that the gains were small, and that they couldn't say if they'd matter in someone's day.^[2]

Dogs? Vets will tell you studies on MSM alone are lacking. Most of the dog data comes from products where it's one ingredient in a mix.^[3]

What the dog studies actually tested

Here's a good example from 2023, published in Frontiers in Veterinary Science. 75 dogs with hip arthritis, 6 weeks, randomized and double-blind with a placebo group. To see how much weight each dog put on her bad leg, the researchers had her walk across a force plate.^[4]

One group got a glucosamine and chondroitin soft chew with 800 mg of MSM in each chew. The others got carprofen (a common anti-inflammatory drug), a placebo, or one of two marine-oil supplements made with green-lipped mussel. At 6 weeks, carprofen and both mussel products beat placebo. The glucosamine, chondroitin and MSM chew sat somewhere in the middle and didn't make that list.^[4] Worth knowing: Pharmalink International paid for the study, and it's the company behind one of the mussel products.

Does that prove MSM is useless? No. Six weeks isn't long, and when MSM shares a chew with three other actives you can't pull its effect out on its own. What it does tell you is that "contains MSM" on a bag doesn't prove much of anything.

Typical amounts of MSM in dog supplements

Nobody has settled on one amount of MSM for dogs, and labels go all over the map. The chew in that 2023 study had 800 mg per chew.^[4] The human knee trial gave people 1,125 mg, three times a day.^[2]

Ours is on the small side, and we'd rather you hear that from us. Pet Nugget lists MSM at 100 mg per 2 soft chews, along with glucosamine HCl at 250 mg, bovine chondroitin at 50 mg and boswellia extract at 25 mg. It's one supporting player in an all-in-one chew. Not a high-strength MSM product.

Please don't treat any of these numbers as a dosing chart for your dog. They're just a good reason to read the mg line (not only the ingredient list) and to bring the actual jar or bag to your vet.

Is MSM safe for dogs? Side effects to watch for

When it's given as directed, most dogs handle MSM fine.^[3] The side effects that do come up are usually mild, and mostly tummy stuff:

• vomiting or diarrhea
• gas
• eating less than usual
• itching or a skin reaction

For people, MSM has had "generally recognized as safe" status since 2007, and up to about 4 grams a day tends to go down fine.^[1] Nice to know. Still human data though.

Where it gets tricky is doubling up. Say she's already on a joint chew and you add an all-in-one chew, or a powder on her kibble... now MSM, glucosamine and friends can stack up without anyone noticing. Vets suggest checking before you combine supplements, and asking before you start anything new if she has a chronic condition or takes medication.^[3] And if she seems off after something new, stop it and call your vet.

Questions to ask your vet before you add MSM

Slower on the stairs, stiff when she gets up from a nap? That's worth an exam before it's worth a new chew, since a supplement doesn't stand in for a diagnosis or a care plan.^[3] Some questions to take with you:

• Should we look at her stiffness first, with an exam or x-rays?
• Is there MSM, glucosamine or chondroitin in anything she already gets?
• With her meds or her diet, is there a reason to skip MSM?
• How do we tell if it's helping, and when do we check again?

If she's reaching the age where these questions come up, here's what changes when a dog reaches middle age. Comparing joint chews? We also dug into how safe collagen chews are for dogs.

Images are illustrative and were created with AI.