Myo-Inositol

With myo-inositol, the dose matters more than the brand. These are the questions our naturopaths ask in store before you buy.

A good fit if

• Your cycle is the reason you're here. That's where the research has its most repeated finding
• You're ready to take 4 g a day, split into two doses, rather than a token amount
• You'd rather start with the form that has nearly all the evidence than a ratio that's still being debated
• You're thinking about preconception health and will check with your practitioner first
• You want something easy to live with. An upset stomach is the usual complaint, and it's typically mild and short-lived

Check with us first if

• You take lithium or valproate. These medicines work partly by lowering inositol in the brain, and the only reassurance so far comes from a small study of fifteen people with no comparison group.
• You take metformin or another diabetes medicine. Myo-inositol is often given alongside them in trials, but your prescriber should know.
• Your kidneys don't work well. Myo-inositol is cleared through the kidneys, and it hasn't been studied in people with kidney problems.
• It's for a teenager. Only one small trial exists, and it didn't meet its main goal.
• You're trying to conceive. Preconception health is a good reason to ask us, and your practitioner should be part of that conversation too.
• You take prescription medicine. Check with your doctor, pharmacist or our naturopaths before you start.

• Myo-inositol. Best known for: Most of the inositol in your body and your food, and the form behind nearly all the research. It increases aromatase and FSH receptor levels in the ovary. Absorption: Trials see effects at two grams taken twice a day. A claim that alpha-lactalbumin boosts absorption relies on a paper that has since been retracted, so we don't repeat it. Typical use: Four grams a day, split into two doses, for twelve weeks to six months.
• D-Chiro-Inositol. Best known for: The form your body makes from myo-inositol, found in blood at about one fortieth the level. High levels increase androgen production and lower aromatase, the opposite of myo-inositol. Absorption: The evidence behind this guide doesn't describe its absorption separately. Typical use: Milligram amounts, alongside myo-inositol. The largest review of this research says to use it with caution on its own.
• Myo-Inositol and D-Chiro-Inositol 40:1. Best known for: Matches the ratio the two forms naturally have in human blood, about forty to one. Absorption: Same as myo-inositol. Typical use: Usually two grams of combined inositols twice a day. It isn't settled whether it works better than myo-inositol alone.

Reference values. There aren't any. Inositol isn't in the NHMRC's nutrient reference values for Australia and New Zealand, because your body makes its own. So there's no recommended intake, adequate intake or upper level for myo-inositol. You'll sometimes see it sold as "vitamin B8", but it isn't a vitamin, so we don't use that name.

Typical supplemental range. With myo-inositol, the dose is the main decision. Almost all the research used 4 g a day, taken as 2 g twice a day, for twelve weeks to six months. In the pregnancy research that split mattered: one review found an effect only in women taking 2 g twice a day, and none in those taking a much smaller 1,100 mg of myo-inositol with 27.6 mg of D-chiro-inositol. Plenty of products supply 500 mg or a single gram, which is below every dose that had an effect in these trials, so check the grams per day, not the grams per capsule.

Upper level. None has been set. Australia's permitted ingredients list (Schedule 1, item 2700) sets no daily maximum, and the NHMRC has no upper level either. Four grams a day is the highest dose regularly studied. Having no limit doesn't mean more is safe.

Worth knowing. Split your dose. The trials gave 2 g twice a day rather than 4 g at once. Myo-inositol leaves your body through your kidneys, and it hasn't been studied in people whose kidneys don't work well. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Cereals: named by Cochrane as a common source. No per-serve figure is available, so none is stated
• Corn: A named source without a published per-serve amount
• Legumes: A named source without a published per-serve amount
• Meat: A named source without a published per-serve amount
• What food can't do: four grams a day is far more than an ordinary diet supplies

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Premature and newborn babies. Don't give it. Six trials in 1,194 infants found no benefit for retinopathy of prematurity (an eye disease) and, in a sensitivity analysis, more deaths (RR 1.55).
• Pregnancy. This is a decision for your practitioner, not something to choose yourself; the evidence is rated low to very low certainty.
• Breastfeeding. We found no trial, review or safety statement. Unknown doesn't mean safe.
• Lithium and valproate. These medicines work by lowering inositol in the brain and nervous system, so check with your prescriber before taking it.
• Metformin and other diabetes medicines. They were often taken together in trials, but your prescriber should know.
• Children and teenagers. There's only one small trial, and it missed its main goal, so there isn't enough data to use it outside clinical supervision.
• Kidney problems. Myo-inositol is cleared by the kidneys, and we found no dosing study in people with reduced kidney function.
• If you take prescription medicines, check with your doctor, pharmacist or one of our naturopaths before you start.