The 40:1 Inositol Ratio Explained (and What Changed in Belle Balance)
Key takeaways
The 40:1 ratio means 40 parts myo-inositol to one part D-chiro-inositol, for example 4,000mg of myo-inositol with 100mg of D-chiro. It is usually described as reflecting the balance of the two forms in blood plasma, and it is used in some combination products and some published research. Myo-inositol on its own, typically at 4,000mg a day, is the other established approach. A label only tells you which one you are holding if it lists each form with its own amount. Belle Balance's current formula is 4,000mg of myo-inositol with no D-chiro.
If you have read about inositol, you have probably met the number 40:1. It is rarely explained. This is the plain version: what it means, where it comes from, how to spot it on a label, and what changed in our own formula.
Sometimes 40:1 appears as a tagline, sometimes as a line in a study's methods section. Either way, it is a description of a formulation, not a quality score. Knowing what it means lets you read any inositol label for what it actually contains.
What is the 40:1 ratio in inositol supplements?
Inositol isn't a single substance. It is a family of related compounds called stereoisomers: the same molecular formula, arranged differently in three dimensions. Two of them appear on supplement labels: myo-inositol and D-chiro-inositol.
A "40:1" product contains both, at forty parts myo-inositol to one part D-chiro-inositol. In practice that usually means 4,000mg of myo-inositol with 100mg of D-chiro-inositol, or 2,000mg with 50mg in a half-size serving.
When a label just says "inositol" with one number, you can't tell which form it is, or whether a second form is in there at all. That is the main reason the ratio is worth understanding: not because one approach is the right one, but because the label should tell you which approach you are buying.
Where the 40:1 figure comes from
The figure is usually described as reflecting the approximate ratio of the two forms in blood plasma. Combination products and some research protocols adopted it on that basis. A 2024 review by Lete and colleagues sets out the rationale for the combination.
It is not the only approach in the literature. A large share of the published human research on inositol uses myo-inositol on its own, centred on 4,000mg a day, usually split into two 2,000mg doses. A 2017 meta-analysis by Unfer and colleagues pooled randomised trials of myo-inositol at around this intake.
So there are two established formulations: myo-inositol alone, and myo-inositol combined with a small amount of D-chiro-inositol, most often at 40:1. Formulators differ on which to use, and neither is "better" on a label. Which suits you is a question for your GP or pharmacist.
(For the broader framework on how supplement labels and research doses line up, see our piece on what "clinical dose" actually means.)
Three things to check on any inositol label
You can read an inositol label for what it contains in under a minute.
1. Is each form listed with its own amount? A label that names myo-inositol (and, if present, D-chiro-inositol) with separate figures is transparent. A single "inositol" number, or a proprietary blend, doesn't tell you what's inside.
2. What is the daily amount of myo-inositol? Much of the published research uses 4,000mg of myo-inositol a day. Some products carry 2,000mg or less per daily serving, which is a different amount from the one most often studied. Check the per-day figure, not the per-capsule one.
3. If D-chiro is listed, divide the myo figure by the D-chiro figure. An answer around 40 means a 40:1 product. A much smaller answer means proportionally more D-chiro, which is a different formulation from the 40:1 products rather than a stronger version of them. No D-chiro line at all means a myo-only product, which is a legitimate, well-researched approach in its own right.
Once you've chosen a product, when and how to take it is the next practical question. Not every "inositol" on a label is the same molecule, either: we break down the forms, and why "DC95" isn't D-chiro at all, in myo-inositol vs D-chiro-inositol vs DC95.
What changed in Belle Balance
Earlier batches of Belle Balance included D-chiro; the current formula doesn't.
Each sachet of the current formula contains 4,000mg of myo-inositol, with magnesium (as magnesium glycinate, 150mg), vitamin B6 (as pyridoxal-5-phosphate), chromium, vitamin C, rhodiola rosea extract, shatavari extract and cranberry extract, in one cranberry-flavoured drink. Every amount is printed on the pouch.
If the 40:1 combination specifically matters to you, look for a product that lists both myo-inositol and D-chiro-inositol with their own amounts. We compare what's available in the UK in Ovasitol in the UK: availability and alternatives.
One Last Thought
The 40:1 ratio is a detail worth understanding, not a badge worth chasing. It tells you a product combines two forms of inositol in a particular proportion. A myo-only label tells you something different, and just as useful.
Whatever you choose, the principle is the same: the label should list each form and its amount, so you know exactly what you are taking.
Frequently Asked Questions
What does 40:1 mean in inositol supplements?
It means 40 parts myo-inositol to one part D-chiro-inositol, for example 4,000mg of myo-inositol with 100mg of D-chiro. It's usually described as reflecting the approximate ratio of the two forms in blood plasma, and it's used in some combination products and some published research.
Where does the 40:1 ratio come from?
The figure is usually attributed to the approximate balance of myo-inositol and D-chiro-inositol in blood plasma, and combination products and some research protocols adopted it on that basis. A 2024 review by Lete and colleagues sets out the rationale for the combination.
Is myo-inositol alone a recognised approach?
Yes. A large share of the published human research on inositol uses myo-inositol on its own, typically at 4,000mg a day, usually split into two doses. Combination products with D-chiro-inositol, most often at 40:1, are the other established approach. Which suits you is a question for your GP or pharmacist.
How can I tell if an inositol supplement uses the 40:1 ratio?
Check that the label lists myo-inositol and D-chiro-inositol with separate amounts. If only myo-inositol is named, it's a myo-only product. If both are listed, divide the myo amount by the D-chiro amount: about 40 means 40:1, which is roughly 100mg of D-chiro per 4,000mg of myo-inositol.
Does Belle Balance use the 40:1 ratio?
No. Earlier batches of Belle Balance included D-chiro; the current formula doesn't. Each sachet contains 4,000mg of myo-inositol, with magnesium glycinate, vitamin B6, chromium, vitamin C, rhodiola, shatavari and cranberry extract.
About the authors
Anna Reeve & Greg Reeve founded Evori in 2026 after two years researching why mainstream women's supplements consistently underdose the ingredients their labels reference. Belle Balance and Femme Flora are their answer to that gap: formulated to the doses and forms the research actually uses, with every amount printed.
Editorial note: this article is educational and does not constitute medical advice. If you have specific health concerns, speak with a qualified healthcare professional.
The full 4,000mg of myo-inositol. In one daily sachet.
Belle Balance, with magnesium glycinate and vitamin B6, in one cranberry drink.