Walk into any barn and open a few feed room cabinets. You’ll find a small pharmacy. Joint supplements, gut supplements, calming supplements, hoof supplements, coat supplements, magnesium, MSM, omega-3s, probiotics, biotin, herbs, amino acids — sometimes twelve products on one horse.
Most of it is producing very expensive urine.
That’s not a knock on the people buying these products. It’s a knock on an industry that has gotten very good at making riders feel irresponsible if they don’t supplement. The marketing is smart, the packaging is beautiful, and the testimonials are compelling. But anecdote is not data, and “he seemed better after I started it” is not a clinical outcome.
Here’s how I actually think about supplements — and what I’ve landed on after years of working with sport horses, reading research, and talking to vets who are willing to say the quiet part out loud.
The One Question That Cuts Through Everything
Before you buy anything, ask: Is my horse’s base diet actually adequate?
The vast majority of supplement purchases are attempts to compensate for a diet that is missing something foundational. A horse eating poor-quality hay that’s been tested at low magnesium isn’t going to be fixed by a $90/month magnesium supplement if the hay isn’t also addressed. You’re just adding cost on top of a problem that hasn’t been solved.
Get your hay tested. It’s cheap. It tells you more than any supplement label ever will. Once you know what your forage is providing — and what it’s not — you have an actual basis for supplementing. Without that number, you’re guessing.
Same goes for your grain. Read the tag. (I wrote a whole breakdown of how to actually read a horse feed tag if the small print makes your eyes cross.) Most commercial feeds are formulated to meet your horse’s nutritional requirements at a certain feeding rate — and most horses aren’t being fed at that rate. So you’re under-feeding a complete feed and then supplementing on top, which means you’re paying twice for the same nutrition and still not hitting the mark.
Fix the diet first. Supplement second, and only where there’s an actual gap.
What Actually Has Evidence Behind It
This is not an exhaustive research review. It’s the short list of categories where the science is solid enough that I’m comfortable recommending them to the riders I work with.
Joint support (targeted, not blanket)
The research on glucosamine and chondroitin in horses is more equivocal than the marketing suggests. However, hyaluronic acid and certain omega-3 fatty acids (particularly those from marine sources) have reasonable supporting evidence for joint health and reducing systemic inflammation. If your horse has a documented joint issue, talk to your vet about injectable options alongside oral support — the oral stuff alone rarely moves the needle as much as people hope.
What I’ve seen actually work: a good-quality omega-3 supplement using flaxseed or fish oil, paired with appropriate management. Affordable, unglamorous, effective.
Gastric support
Gastric ulcers are genuinely common in sport horses. A horse in regular work, trailering, competing, and living on a schedule that doesn’t match their physiology is at real risk. Omeprazole (the active ingredient in GastroGard and its generic equivalents) is the only treatment with solid clinical evidence. Hindgut support products are a separate category — if your horse has been scoped and has a confirmed hindgut issue, talk to your vet about what’s actually indicated.
What I’m skeptical of: the sprawling category of “gut support” products that promise to do everything at once. Pick a lane based on what your vet has actually found.
Biotin for hooves
This one is legit, but with a caveat: biotin takes six to nine months to show up in grown hoof wall. If you started it in January and think you’re seeing results in April, you’re seeing something else. Stick with it long-term or don’t bother.
Electrolytes in summer
Not a supplement so much as a management tool, but worth saying clearly: horses sweating hard in summer heat need electrolytes replaced, not just salt. Especially in the southeast. Especially right now, in late July. This is one category where I’m not equivocal — if your horse is doing significant work in this heat, they need more than a salt block.
What I’m Genuinely Skeptical Of
Most calming supplements. Some horses are tense because they hurt. Some are tense because their training hasn’t given them a way to organize their nervous system under pressure. Some are genuinely reactive by temperament. A supplement that “takes the edge off” may be masking a pain response or a training gap — and if you’re relying on it to get through a ride, that’s worth investigating rather than managing around.
If your horse is tight through the back and bracing into the contact, that’s not a magnesium deficiency. That’s a body that hasn’t learned how to carry itself — and no supplement addresses it. The Unlocking the Back of a Stiff Horse ride-along is what I’d point you toward instead: it’s a 16-minute audio lesson that walks through a warmup using neutral spine walk and trot work, shoulder-in, leg yield, and transitions specifically designed to help a horse that braces and leans on the inside shoulder. No supplement required.
Coat and bloom products. If your horse’s coat looks dull, check their fat intake, their protein quality, and their overall caloric status. A dull coat is almost always a diet story, not a product story.
Anything marketed with before-and-after photos as its primary evidence. Photos are not data. Summer coat versus winter coat is not a supplement result.
The Supplement That’s Actually Missing From Most Buckets
Time.
Most horses are under-recovered, under-slept relative to their workload, and living in management conditions that create chronic low-grade stress. No supplement addresses that. Better turnout, more forage availability, less stall time, a training program that builds fitness gradually rather than asking for peak performance on under-prepared bodies — these things do more for long-term health than most of what’s in your feed room.
I talk about the nervous system side of this regularly on the podcast — because so much of what we attribute to physical problems in horses actually has a regulation component that we’re not addressing.
A Framework for Buying Decisions
Before you add anything new:
- Do you have a hay analysis? If not, start there.
- Is your horse being fed the recommended amount of their current feed? If not, address that first.
- Is there a specific, documented issue this supplement addresses? Not “I think he might benefit from” — an actual identified gap.
- Has your vet weighed in? A vet who will actually tell you if something is worth it is worth their weight in gold. Find one.
- Are you willing to trial it for a genuine amount of time with objective benchmarks? “He seems better” after two weeks is not a benchmark.
If the answer to most of those is no, put the supplement back on the shelf. Come back when you have more information.
Where Gear Fits In
Two product categories I do think are worth researching for horses with specific needs: therapeutic support products (you can find my honest reviews in the gear review section of the blog) and targeted recovery tools for horses in heavy work. I have opinions on both, but that’s a separate conversation — and one where the individual horse’s situation matters a lot.
The short version: spend your money where you have evidence, and be honest with yourself about whether you’re buying results or buying reassurance. There’s no shame in the latter — we all do it. But naming it for what it is helps you make smarter decisions the next time around.
Looking for more practical tools you can use in the saddle? The ride-along library is a growing collection of audio lessons designed to play while you ride — no screen-watching required. If you’re working through body and movement questions with your horse, it’s a good place to start.
