Inositol is a substance from the group of cyclic sugar alcohols that the body makes itself and also gets from food. It is often called "vitamin B8" and confused with inosine (Riboxin), although these are different compounds with different formulas and status. Below: what inositol and myo-inositol are, where they occur, what may be said about them in the EU and how to compare supplements by the label — the doses differ by a factor of thousands.
Contents
- What inositol is
- Why it is called "vitamin B8"
- Inositol vs inosine: the difference
- Where inositol is found in food
- What may be said about inositol in the EU
- How to choose an inositol supplement: form and dose
- Safety
- Frequently asked questions
- Sources
What inositol is
Chemically, inositol is cyclohexanehexol: a ring of six carbon atoms, each carrying a hydroxyl group. Its formula is C6H12O6, the same as glucose, but the structure is different. Inositol has nine spatial forms; the one most common in nature and in food supplements is myo-inositol, less often D-chiro-inositol.
The body also makes myo-inositol itself, from glucose. That is why inositol is no longer classed as a vitamin: vitamins are substances the body does not make in sufficient amounts on its own.
Why it is called "vitamin B8"
The name "vitamin B8" dates from the time when inositol was counted among the B vitamins. Once it became clear that the body makes it itself, the name lost its scientific standing, but it still appears on labels and in articles.
Adding to the confusion, French sources use "vitamin B8" for biotin (also known as vitamin B7, or H). So if the label of an imported product says "B8", check the full name of the substance in the ingredients: it may be inositol or biotin. More on biotin in our guide to collagen, biotin and zinc.
Inositol vs inosine: the difference
Inositol and inosine differ by a couple of letters, but they belong to different classes of substances. Inosine is a nucleoside: a molecule made of the nitrogenous base hypoxanthine and the sugar ribose. In free form it occurs in muscle tissue and yeast, and its phosphorylated form, inosinic acid, is used in the food industry as an additive that gives food an umami taste.
| Feature | Inositol | Inosine |
|---|---|---|
| Class of substance | cyclic sugar alcohol | nucleoside (hypoxanthine + ribose) |
| Formula | C6H12O6 | C10H12N4O5 |
| Other names | myo-inositol, inosite, "vitamin B8" | Riboxin (trade name) |
| Related E numbers | none | E630 inosinic acid, E631 disodium inosinate |
| EU health claims | none | none |
In Russia and several other countries inosine is also sold as a medicine under the name Riboxin, which is why a search for "inosine" brings up many package leaflets. They have nothing to do with inositol.
Where inositol is found in food
A US study from 1980 measured the myo-inositol content of 487 foods. The highest amounts were found in fruits, beans, grains and nuts, and fresh vegetables and fruits contained more than frozen and canned ones.
A diet made up of ordinary foods supplied 225 to 1,500 mg of myo-inositol a day per 1,800 kcal. For comparison: supplements in our catalogue where inositol is the main ingredient contain 300 to 2,480 mg per daily dose, while complexes and multivitamins contain 0.35 to 25 mg.
What may be said about inositol in the EU
In the EU, the health benefits of foods and food supplements may only be described with authorised claims; the main list of them is Regulation (EU) No 432/2012. There are no authorised claims for inositol or inosine, so we do not write what to take them "for" — we describe the composition and the dose. If an advert promises a specific effect from inositol, that claim is not on the EU list of authorised claims.
Substances that often share a formula with inositol are a different matter: choline, folate and B vitamins do have authorised claims. Their exact wording is in the regulation itself; the link is in the Sources section.
How to choose an inositol supplement: form and dose
On the label, look at three things: which form of inositol it contains (myo-inositol, D-chiro-inositol or both), how much is in the daily dose rather than in one capsule, and how many daily doses the pack holds. Here is how this looks for products in our catalogue:
| Product | Form | Per daily dose | Pack |
|---|---|---|---|
| Swanson Inositol 650 mg, 100 capsules | inositol | 650 mg (1 capsule) | 100 doses, 65 g of inositol |
| OstroVit Inositol Plus, 120 capsules | myo- and D-chiro-inositol 40:1, folate | 2,480 + 62 mg (4 capsules) | 30 doses, about 76 g of inositol |
| OstroVit Choline + Inositol, 120 tablets | myo-inositol, choline | 300 mg (2 tablets) | 60 doses, 18 g of myo-inositol |
| VITATEKA Menoplus+ marine collagen | inositol as part of a complex | 15 mg in 25 ml | 500 ml |
| Ultra+, WOMAN 50+, MAN 50+ and MAN Testosterone VITATEKA | inositol as part of a multivitamin | 25 mg in 15 ml | 500 ml |
| Herbin Bee & Immuno, 10 bottles of 10 ml | inositol as part of a complex | 0.35 mg (1 bottle) | 10 bottles |
The table shows the main point: inositol as part of a multivitamin and inositol as a dedicated supplement are two different things. The 25 mg in a liquid multivitamin is 26 times less than in one Swanson capsule and about a hundred times less than in the daily dose of OstroVit Inositol Plus. To compare prices, divide the price of the pack by the grams of inositol it contains.
The "40:1" on the pack is the ratio of myo-inositol to D-chiro-inositol in the daily dose: in OstroVit Inositol Plus that is 2,480 mg and 62 mg. The folate in the same formula is vitamin B9 in the form of L-methylfolate; if folate is what you are after, there are separate products too, for example FarmGroup folic acid with vitamins B6 and B12. Similar products are in the "B vitamins" and "Multivitamins" sections.
Safety
- Pregnancy and breastfeeding. Use any inositol supplement during this time only after consulting a doctor.
- Medicines and chronic conditions. If you take medicines or are under medical supervision, discuss the supplement with your doctor before you start.
- Dose. Do not exceed the daily dose on the label. If you take several products, add up the inositol in all of them — especially if one of them is a dedicated inositol supplement.
- Inosine and inositol are not interchangeable. If a doctor has prescribed you a medicine with inosine (Riboxin), do not replace it with an inositol supplement, or vice versa.
In short
- Inositol is a cyclic sugar alcohol; the main form in nature and in supplements is myo-inositol.
- "Vitamin B8" is an outdated name for inositol; French sources use it for biotin.
- Inosine (Riboxin) is a different substance, a nucleoside; E630 and E631 are derivatives of inosinic acid used as umami flavour additives.
- The EU has no authorised health claims for inositol or inosine.
- Compare the amount per daily dose: from 0.35–25 mg in complexes and multivitamins to 300–2,480 mg in supplements where inositol is the main ingredient.
Frequently asked questions
Are inositol and inosine the same thing?
No. Inositol is a cyclic sugar alcohol (C6H12O6); inosine is a nucleoside made of hypoxanthine and ribose (C10H12N4O5). The names are similar, but they are different substances.
What is myo-inositol?
It is the most common form of inositol in nature. It is usually the form named on supplement labels, sometimes together with D-chiro-inositol.
What does "40:1" on the pack mean?
It is the ratio of myo-inositol to D-chiro-inositol in the daily dose. For example, OstroVit Inositol Plus contains 2,480 mg of myo-inositol and 62 mg of D-chiro-inositol.
Is inositol a vitamin?
No. It used to be called "vitamin B8", but the body makes inositol itself, so it is no longer classed as a vitamin.
Is Riboxin inosine?
Yes, Riboxin is the trade name of a medicine containing inosine. It has nothing to do with inositol.
Can you get inositol from food?
Yes. Fruits, beans, grains and nuts contain the most myo-inositol; in a 1980 study an ordinary diet supplied 225 to 1,500 mg a day.
Sources
- Regulation (EU) No 432/2012 — the list of health claims authorised in the EU.
- Regulation (EC) No 1333/2008 — food additives, including E630 and E631.
- PubChem: myo-inositol and inosine — structure and formulas.
- Clements R. S., Darnell B. Myo-inositol content of common foods: development of a high-myo-inositol diet. Am J Clin Nutr, 1980.
- VIDAL: vitamin B8 (biotin) — the French name for biotin (in French).
- Composition and doses: product labels on the Vitateka website, October 2026.
Important information
A food supplement is not a medicine and does not replace a varied, balanced diet and a healthy lifestyle. Do not exceed the recommended daily dose. If you are pregnant, breastfeeding, taking medicines or under medical supervision, consult a doctor before use. Keep out of reach of children.
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