What's the best inositol ratio for period regularity?

The ratio that shows up most in inositol research is 40:1, myo-inositol to D-chiro-inositol, the naturally occurring plasma ratio in the body. This is not a marketing number. Not for use during pregnancy; talk with your healthcare provider before starting any new supplement, especially while breastfeeding or managing a medical condition. Myo-inositol and D-chiro-inositol are two related compounds studied for their role in supporting hormonal wellness, ovarian health, and menstrual cycle regularity, and much of the underlying research on ratio comes from studies in women with a specific diagnosis, so it's worth understanding both what the science actually studied and what it means for cycle regularity more broadly.

Where the 40:1 ratio comes from

A clinical trial comparing several myo-inositol to D-chiro-inositol ratios in women with polycystic ovary syndrome (PCOS) found that the 40:1 ratio, matching the ratio normally found in blood plasma, was more effective than other tested ratios at restoring ovulation and normalizing certain hormone markers in that specific patient group. A separate review of the combined myo-inositol/D-chiro-inositol therapy literature reached a similar conclusion: supplementing in the physiological 40:1 ratio tends to produce better results than other ratios in the populations studied.

That research was conducted specifically in women with PCOS, a distinct endocrine condition, and it does not mean an inositol supplement diagnoses, treats, or manages that condition. What it does establish is that ratio matters mechanically: myo-inositol and D-chiro-inositol work through different pathways in the body, and getting the balance wrong, specifically taking too much D-chiro-inositol relative to myo-inositol, can work against, rather than support, healthy ovarian signaling.

Why does a "normal" cycle vary so much anyway?

The Eunice Kennedy Shriver National Institute of Child Health and Human Development notes that 14% to 25% of women of childbearing age have irregular menstrual cycles, meaning cycles shorter or longer than the typical 21-to-35-day range, heavier or lighter flow, or other associated symptoms. Cleveland Clinic frames a cycle as irregular when its length varies by more than about nine days from one cycle to the next. Irregularity itself is common and has many possible causes, not all of them the same condition, which is exactly why ratio-specific research matters more than a generic "supports hormones" claim.

How this translates to a formula built around ratio

Our 40:1 myo-inositol and D-chiro-inositol blend delivers 2,000 mg of myo-inositol to 50 mg of D-chiro-inositol per serving, matching the physiological ratio referenced in the research above.† It's formulated to support healthy hormone signaling, ovarian health, and menstrual cycle regularity as part of a preconception routine, using structure/function language rather than any claim tied to a specific diagnosis.†

"Every Pink Stork product is not only backed by science, it's also covered in prayer."

— Amy Suzanne Upchurch, Founder and CEO of Pink Stork

Myo Chiro 40:1, formulated to support cycle regularity, is third-party tested and manufactured in cGMP-certified facilities. If cycle regularity, fertility, or ovarian health support is part of your preconception routine, you may also want to look at our fertility gummies with methylated folate and myo-inositol or our organic fertility tea with vitex and red raspberry leaf.

Related reading: does the ratio in your inositol supplement actually matter and does an irregular cycle mean something is wrong with me.

Frequently asked questions

Is 40:1 really the "best" inositol ratio?

Research comparing multiple ratios found that 40:1, matching the body's natural plasma ratio, produced better results than other tested ratios in the specific patient populations studied. It's the most researched ratio for this purpose, though individual needs vary.

Does this research mean inositol treats PCOS?

No. This information describes published research and is not a claim that any Pink Stork product diagnoses, treats, cures, or prevents any condition. Talk with a healthcare provider about any diagnosed condition.

How common are irregular periods?

The NICHD estimates 14% to 25% of women of childbearing age experience irregular menstrual cycles.

Can I take Myo Chiro 40:1 while pregnant?

No. It is not intended for use during pregnancy. Talk with your healthcare provider before use while breastfeeding.

What's the difference between myo-inositol and D-chiro-inositol?

They're related compounds that work through different pathways in the body; myo-inositol is more associated with ovarian signaling, while D-chiro-inositol is more associated with insulin-related pathways.†

† These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Always consult your healthcare provider before starting any new supplement, especially during pregnancy, breastfeeding, or while managing a medical condition. Keep out of reach of children.