Inositol
Browse inositol supplements: myo-inositol in powder and capsules, plus 40:1 combinations with D-chiro-inositol. We explain which form fits which goal, the doses used in research and how to start without stomach upset.Read more →
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Choosing between myo-inositol and 40:1 combinations
Inositol is a sugar alcohol that your body makes itself, mostly from glucose. You also get it from food: citrus fruit, beans, nuts and wholegrains. Labels sometimes call it vitamin B8, but it is not a vitamin, because your body does not depend on food for it. Inside cells it works as a messenger, passing on signals from hormones such as insulin. About 95% of the free inositol in the body is the myo form, which is why most supplements start there.
Inositol itself has no authorised health claim in the UK or the EU. EFSA assessed inositol and cognitive function and judged the evidence insufficient. Formulas therefore borrow their wording from added nutrients. Vitamin B6 contributes to the regulation of hormonal activity, and chromium contributes to the maintenance of normal blood glucose levels. Those claims belong to those nutrients, not to inositol. If a pack promises more, read the ingredient panel instead of the front label, or compare products with vitamin B6 on their own.
The forms that genuinely differ
- Myo-inositol: the most studied form and the base of nearly every serious formula.
- D-chiro-inositol: used in small amounts. In blood, myo and D-chiro sit at roughly 40 to 1, which is where 40:1 blends come from. More D-chiro is not better.
- Myo with B6, folate or chromium: for people who want the approved claims of those nutrients alongside.
- Powder or capsules: servings of 2,000 to 4,000 mg mean four to eight capsules of 500 mg. Powder dissolves in water and tastes faintly sweet, which is simpler at that level.
How we choose the inositol we stock
We look at three things: the form, the amount per serving and the combinations that make sense. Myo-inositol is the base we expect to see, with D-chiro-inositol only in small proportions. We prefer servings you can realistically reach, so a scoop of powder or capsules of 500 mg or more, rather than 250 mg capsules that need eight a day. Where vitamin B6 is added, we check it stays within sensible limits. We buy directly from the brands, our compliance team checks every label before it goes live, and we test batches ourselves alongside independent labs. See how we select brands and products.
Who it suits and what to expect
Most inositol formulas are built around cycle and metabolic support, which is why they sit close to our chromium options and to B-vitamin blends. Plain myo-inositol powder is also chosen by people who simply want one ingredient, no additives and full control over the amount.
Be realistic about timing. Most studies ran for twelve to twenty-four weeks before measuring anything, so give it at least two to three months of daily use before you judge it. Because inositol draws water into the gut, a high starting amount can cause mild bloating or loose stools. Starting lower, splitting the serving and taking it with a meal usually settles that within a week. If you are pregnant, breastfeeding or taking prescribed medication, check with your GP first. Products aimed at cycle support sit in our range chosen for women.
Frequently asked questions
What exactly is inositol?
Inositol is a sugar alcohol, not a vitamin, although labels still call it vitamin B8. Your body makes it from glucose, and you also get it from citrus fruit, beans, nuts and wholegrains. In grains much of it is bound as phytate, which the body absorbs poorly. Inside cells it acts as a messenger that helps pass on hormone signals, including insulin signals. Roughly 95% of the free inositol in the body is the myo form.
Does inositol have an approved health claim in the UK?
No. EFSA assessed a claim on inositol and cognitive function and found the evidence insufficient, so no authorised claim exists for inositol itself. Any health wording you see on a pack therefore comes from other ingredients: vitamin B6 contributes to the regulation of hormonal activity, chromium contributes to the maintenance of normal blood glucose levels, folate contributes to normal blood formation. We prefer to say this plainly, so you know what you are actually buying.
Which form of inositol should I choose?
That depends on whether you want one ingredient or a combination. Myo-inositol is the base in almost all research. D-chiro-inositol is used in small proportions alongside it, not on its own at high amounts.
| Option | What it contains | Usually chosen for |
|---|---|---|
| Myo-inositol | Myo only | Single-ingredient use, full control |
| 40:1 blend | Myo with a little D-chiro | Mirroring the natural blood proportion |
| Myo with B6 | Myo plus vitamin B6 | Hormonal activity claim of B6 |
| Myo with chromium | Myo plus chromium | Blood glucose claim of chromium |
How much do people usually take, and when?
Clinical studies most often used 2,000 to 4,000 mg of myo-inositol per day, split into a morning and an evening serving at the higher end. Much larger amounts have been studied for other purposes, but they are not the norm on supplement labels. Follow the serving on the pack you buy. Taking it with a meal and building up over the first week tends to be gentler on the stomach than starting at the full amount.
Powder or capsules: which is more practical?
It is mostly a question of serving size. At 500 mg per capsule, a 4,000 mg serving means eight capsules a day, which many people give up on. Powder covers the same amount in one level scoop, dissolves in water and tastes faintly sweet. Capsules win on convenience when you travel or when your serving is 1,000 to 2,000 mg. If you prefer scoops, our powdered supplements are filtered separately.
Can inositol upset your stomach?
It can, and there is a simple reason. As a sugar alcohol, inositol pulls water into the intestine, so higher amounts can cause bloating, wind or loose stools. In studies at 2,000 to 4,000 mg a day these reports were low and mild. Three things help: start with a smaller serving for the first week, split it across the day, and dissolve powder fully instead of swallowing clumps. Most people find it settles within a few days.
How long before I notice anything?
Longer than most people expect. The majority of trials ran for twelve to twenty-four weeks before measuring results, so plan on two to three months of consistent daily use before drawing conclusions. Some people notice small changes in energy or mood sooner, but that is subjective and easy to misread. Stopping after three weeks because nothing happened does not give the ingredient a fair test. Set a reminder and keep the routine simple.
What should I check on the label of a combination formula?
Check the amount of myo-inositol per serving, not per capsule, and how many capsules that serving takes. Check the proportion of D-chiro-inositol: a small share, not a large one. Then check the added nutrients, because vitamin B6 and chromium stack with any multivitamin you already take.
| Nutrient | NHS advice for supplements |
|---|---|
| Vitamin B6 | No more than 10 mg a day |
| Chromium | 10 mg or less a day |
