I asked my vet to read every metabolic supplement label in my barn. What she said next changed how I shop forever.

I have been buying metabolic supplements for my Welsh cob mare for almost six years. Three different brands. Eighteen months on the most popular imported product. Two short detours into US-made flavonoid powders. About $4,200 in cumulative spend, give or take, on supplements alone.

And until last November, I had genuinely never read the back of any of those bags.

I read the marketing. I read the customer reviews. I read the dosing instructions. I did not read — really read, with my reading glasses on, in the way a vet reads a label — the actual ingredients panel. I assumed, like most owners, that if a supplement company put a flavonoid blend in a bag and slapped a horse on the front, the contents were broadly what the marketing said they were.

That was naïve. Here is what I learned in the weeks after my vet asked me a single, simple question.

The question

It was during Onyx’s annual exam. My vet — Dr. Helena Mercer, who has been my mare’s primary care veterinarian for four years and is one of the few people in my barn whose opinion I take without question — picked up Onyx’s bag of imported flavonoid powder and turned it over in her hands.

“Caroline,” she said. “How many milligrams of quercetin are in this scoop?”

I stared at her. “I… don’t know. It says it has quercetin.”

“Right,” she said. “But how much?”

I looked at the bag. The ingredient panel said, in full: “Proprietary flavonoid blend (including dihydromyricetin, quercetin, chlorogenic acid), organic yeast culture, organic green tea extract.” That was it. There were no milligram figures. No dose breakdown. No clinical strength disclosed. Three flavonoids were named — but not dosed.

Helena explained something I have since confirmed with two other vets and a graduate of an equine nutrition program: the words “proprietary blend” are not a legal requirement, a regulatory category, or a quality indicator. They are a marketing choice. A supplement company can put the milligrams on the label any time they want. The reason most metabolic supplement companies don’t is that the doses, once disclosed, would be a significant part of the conversation about what the product is actually worth.

I asked Helena: “So how do I know if my supplement is doing anything?”

She said: “Read the label. If you can’t read the label, it’s not doing what the marketing says it’s doing.”

The four questions I now ask before I buy any supplement

Helena walked me through the four questions she now tells every client to ask before they spend money on a metabolic supplement. I am sharing them here because they have completely changed how I shop — not just for Onyx, but for every supplement decision I make for my horses.

I went home that night and lined up every supplement in my feed room. Onyx’s bag. My gelding’s hoof supplement. A general electrolyte. A joint blend I had been adding to my old jumper’s feed for years.

Three of the four had the words “proprietary blend” somewhere on the label.

I had been buying four supplements regularly for years, and I had no idea what I was actually feeding my horses at the milligram level.

The brand that named every milligram

A week later, Helena mentioned a brand she had started recommending to her metabolic clients — a small family operation out of Lexington, Kentucky, called Goodbarn. She said the thing that caught her attention was that their flavonoid product, MetaSupport, named every milligram of every active flavonoid on the back of the bag.

I looked it up. She was right. The label was — and this is going to sound absurd in 2026 — startlingly transparent. The back of the bag listed four named flavonoids, each with a specific milligram dose, each within the published research range.

I want to be careful about how I describe what happened next, because I know how this kind of article reads. But here is what I can tell you, plainly and without embellishment.

A side-by-side comparison nobody wants to publish

I sat at my kitchen table one night and wrote out a comparison of what I had been feeding my mare on the imported supplement versus what MetaSupport disclosed. I have permission to share it here. I’m not going to name the imported product because that’s not the point — and frankly, the same comparison would apply to most metabolic supplements on the market right now.

I want to acknowledge what this comparison does and doesn’t say. It doesn’t say my old supplement was a scam. It doesn’t say the company is dishonest. The company could be feeding clinical doses of every flavonoid for all I know — that’s the entire point: I don’t know. They have chosen, deliberately, not to tell me.

What it does say is that for the same general product category — a metabolic flavonoid blend for horses — one company chose to tell me exactly what I was buying and one company chose not to. One of them charges me $1.05/day. The other charges me more than twice that.

If you’re a horse owner reading this, you can decide for yourself what to make of that. I’ve already decided.

Why I’m writing this

I’m not a journalist. I’m a horse owner who got fed up. I’ve been on the receiving end of the metabolic-supplement industry for six years and I genuinely did not understand, until very recently, how casually the industry treats the question of what is in the bag.

I’m also writing this because Onyx is doing better than she has in years, and a meaningful part of that is the supplement I switched to. Her insulin retested at 31 µIU/mL six months after I switched. Her crest has softened. She is grazing managed pasture this spring with a muzzle and has not been sore-footed once. I am not claiming the supplement did all of that — management still matters most — but I am saying that for the first time in six years, the supplement seems to actually be doing what the marketing says it does.

And I’m writing this because I think every horse owner deserves to know what they’re feeding. Not approximately. Not generally. Not “contains the things.” The actual milligrams. On the label. Where you can read them.

What other owners are saying

If you take one thing from this article

Go to your feed room. Pick up your metabolic supplement bag. Turn it over. Read the back, the way you’d read a prescription bottle — closely, with your reading glasses on. Find the active ingredients. Find the doses.

If the bag tells you the milligrams: good. That’s a company that respects your decision-making. Stay with them.

If the bag says “proprietary blend” and doesn’t disclose the doses: you have a decision to make. Maybe your supplement is working. Maybe the doses are clinical. Maybe you’ve gotten lucky. Or maybe — and this was my situation — you’ve been paying a premium for ambiguity for years and you didn’t know.

Either way, you deserve to know. Your horse deserves a supplement on the label.

MetaSupport offers a 60-day promise: if your horse’s crest hasn’t softened in 60 days, they refund the bag. No questions. I have never had to use it, but knowing it existed was what made me willing to try the brand in the first place. I think that promise tells you almost everything you need to know about a supplement company — whether they’re willing to take the risk that the product won’t work, or whether they want you to take it.

Read the label.

— Caroline Whitmore
Aiken, South Carolina