- MunchMetrics
- Posts
- Berberine: The "Natural Metformin" With a Supplement Problem
Berberine: The "Natural Metformin" With a Supplement Problem
...over half of tested products contain less than 40% of labeled berberine
Anastasia Balashova
April 04, 2025
Berberine is a bright yellow, bitter-tasting compound found in several plants like barberry, goldenseal, and Oregon grape. It's been used in traditional Chinese and Ayurvedic medicine for centuries, treating everything from infections to digestive issues.
But modern science has discovered something ancient healers never knew — berberine has quite some effects on metabolism. And if you struggle with blood sugar, cholesterol, or metabolic issues, this could actually matter to your health. So, of course, search "berberine" on Amazon and you'll find over 1,000 products promising miracle-adjacent benefits. While it sounds great, look deeper (which I did, so you don't have to) and you'll find more red flags than a Soviet parade.
TLDR: Berberine might legitimately help your metabolism, but the supplement industry selling it might not have buyers' best interest in mind. I found a possibly fictional quality director signing certificates, companies with F-ratings from the BBB, and shamelessly inflated scientific credentials. Add berberine's abysmal <1% absorption rate to the shocking revelation that over half of tested products contain less than 40% of labeled berberine, and you're potentially popping expensive yellow placebos. Let’s unpack all of it.
Table of Contents
What exactly is berberine and why should you care?
Multiple well-designed clinical trials show berberine can lower long-term blood sugar (HbA1c) by 0.5-1 percentage points — similar to prescription medications. It works partly by activating an enzyme called AMPK, nicknamed the metabolic "master switch" that also happens to be a target of the diabetes drug metformin. In fact, berberine's effects are so similar to metformin that some researchers literally compare those two.
While others found that 1000mg of berberine daily worked as well as metformin at lowering blood sugar in type 2 diabetics.
Beyond blood sugar, berberine also improves insulin resistance, lowers LDL cholesterol (by about 15-20 mg/dL), and reduces triglycerides. What's more, these effects aren't small statistical blips — they're clinically meaningful changes that could impact your health.
But when it comes to something natural and healthy that can be turned into a supplement, there’s always a catch — getting all these benefits depends entirely on whether your berberine supplement contains, well... actual berberine. And based on my investigation, there's a disturbing chance it doesn't.
A closer look at Amazon's top berberine sellers
Let's look at the top-selling berberine brands. What I found ranges from questionable to comical to criminally deceptive.
NOW Supplements: exposing the industry while selling their own solution
NOW Supplements offers Berberine as Glucose Support ($24.49 for 90 softgels, $0.27 per count) and it stands out for two reasons.
First, they combine 400mg berberine with 700mg MCT oil and 238 mg of capric acid, claiming enhanced absorption. And even though sodium caprate would be a more appropriate ingredient to use in this case, combining medium-chain triglyceride (MCT) oil with capric acid (also known as decanoic acid) can provide a similar fatty acid profile to sodium caprate, which is the sodium salt of capric acid.
Second, they're the only company that consistently delivered 100% of labeled berberine content in testing.
NOW Foods decided to test their competitors' products. They purchased over thirty berberine supplements from Amazon and Walmart, then tested their actual berberine content through high-performance liquid chromatography (HPLC).
What they found should make every consumer furious: every single brand except NOW tested below 100% of claimed potency. More than half (18 of 33) contained less than 40% of claimed berberine, and seven products had virtually no berberine at all (1% or less of label claim).
To make sure their findings weren't biased, NOW sent duplicate samples to an independent third-party lab (Alkemist Labs) which confirmed the results.
Similar issues were uncovered by ConsumerLab, which found quality problems in nearly half of berberine and goldenseal supplements they tested.
And not to sound like NOW’s shill, but looking through their employees you can see that they actually employ real scientists with relevant credentials. Their scientific team includes PhD food scientists and regulatory experts. They maintain in-house testing labs that are ISO/IEC 17025:2017 accredited — a level of quality verification that's rare in the supplement world.
The company states they spent "significant resources" conducting testing to expose fraud and protect consumers, noting that berberine's rising popularity has attracted "opportunistic sellers with little interest in offering quality, effective products." Based on the testing results, that appears to be an understatement. So, thank you, NOW Foods, for doing all that heavy lifting for us.
NutriFlair: the empty envelope company
NutriFlair Premium Berberine ($25.63 for 120 capsules, $0.21 per count) leans on "premium" marketing language while delivering some of the industry's worst customer service.
Their Better Business Bureau profile shows an "F" rating with multiple unanswered complaints. Customers report bizarre experiences like receiving empty envelopes instead of products, and phone lines that leave callers in perpetual voicemail limbo.
One customer wrote: "Hello, I ordered a bottle of supplements from this company last month... Oddly, an envelope, not a box, arrived a week later from NutriFlair. When I opened the envelope it was empty! No supplement bottle, and no packing slip." When they tried to reach customer service: "No phone number on the website that I can find. I'm thinking this isn't a legitimate business."
Their reputation problems don't end there. Analysis from Fakespot suggests that 40% of their 85,000+ reviews across platforms are likely unreliable — a strong indicator of review manipulation.
When Reddit users asked NutriFlair for proof of testing, the company flat-out refused, claiming their third-party certifications were "proprietary information." This is corporate speak for "we don't want you to see what's actually in our products."
My attempts to find legitimate scientific credentials among NutriFlair's staff came up empty. Their Amazon content reads like it was written by marketing AI rather than nutrition experts. And given the industry-wide quality issues, I'm deeply skeptical that their berberine capsules contain the full 1200mg claimed on the label.
THORNE: white coats, inflated credentials, and people in suits
THORNE’s Berberine ($39.90 for 60 capsules, $0.67 per count) is the most expensive option in the top search results, combining regular berberine HCl (450mg) with a proprietary "Berberine Phytosome" (550mg) that supposedly improves absorption.
Since this brand is usually regarded as the unspoken golden standard in the world of supplements, I’ve spent a bit more time trying to make sure it’s as good as it’s perceived.
Thorne markets itself as a "science-first" company, pointing out partnerships with prestigious research institutions. But to be fair it only looks good on the surface.