Recommended Dosage of Myo- and D-Chiro-Inositol for PCOS
What's the right inositol dosage for PCOS? This guide covers the standard 2,000-4,000mg daily dose, the 40:1 ratio, and safety considerations for effective hormonal balance.
by Eco Hormone Balance Editorial Team · Published August 13, 2025 · Evidence & product details rechecked August 7, 2026
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- Daily dose and serving burden
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Product details and prices checked August 7, 2026 — prices vary by retailer and over time.
Dose questions are where most inositol buying decisions actually happen. The difference between a helpful routine and a confusing one is usually not the brand — it is whether the daily total, the ratio, and the serving burden match what the clinical studies used.
This guide lays out the studied dosages for PCOS: myo-inositol alone, the 40:1 myo-plus-D-chiro combination, and the cautions around D-chiro-heavy formulas.
Quick answer
The most common studied pattern for PCOS is 4,000 mg myo-inositol per day with D-chiro-inositol at the 40:1 ratio — i.e., 2,000 mg myo plus 50 mg D-chiro twice daily.
Myo-inositol alone is typically studied at 2 g twice daily (4 g per day).
Expect to run protocols for roughly three to six months before judging the effect — that is the timeframe of most trials.
The 40:1 combination: what trials used
The systematic review that informed the 2023 international PCOS guideline is built on 40:1-style myo/D-chiro protocols — typically 2,000 mg myo plus 50 mg D-chiro per serving, taken twice daily for about three to six months.
A randomized ratio trial compared several myo-to-D-chiro mixes and found 40:1 best for restoring ovulation, using a standard schedule of 2 g of inositols twice daily.
Myo-inositol alone: the studied dose
A meta-analysis of randomized trials found that myo-inositol supplementation — commonly 2 g twice daily — significantly lowered fasting insulin and HOMA-IR in women with PCOS. Single-ingredient products should be measured against that pattern.
Some studies added folic acid alongside (often 200 mcg twice daily), which is why many products pair inositol with folate.
D-chiro-inositol: dose and caution
In the 40:1 pattern, the D-chiro portion is small — 100 mg per day total (50 mg twice daily). That keeps the ratio aligned with the studied balance.
Higher-D-chiro formulas are a different experiment. Ratio comparisons suggest shifting heavily toward D-chiro reduces the reproductive benefit seen at 40:1, and the evidence on sustained high-dose D-chiro is thin. If a label does not disclose both amounts, that is a reason for caution.
How long to run it, and what to expect
Most trials ran for three to six months. The Cochrane review of inositol for subfertility with PCOS rated the evidence low to very low quality, so results are not guaranteed — but the studied pattern is a useful target.
If you are combining inositol with metformin or adding other supplements, check timing and dosing with a clinician; those combinations are studied separately.
The takeaway: match the studied pattern
4,000 mg myo-inositol per day at a 40:1 ratio, split twice daily, run for three to six months before judging results.
Final verdict
The dosage that makes sense for most PCOS buyers is the one the studies used: 2,000 mg myo plus 50 mg D-chiro twice daily (40:1), or 2 g myo twice daily if you prefer a single-ingredient product. Confirm the label delivers that total, then stay consistent.
What to read next
Finish your research with the guides that explain the formula, then compare the leading products before you commit.
References
- Inositol for Polycystic Ovary Syndrome: A Systematic Review and Meta-analysis to Inform the 2023 Update of the International Evidence-based PCOS Guidelines
- Myo-inositol effects in women with PCOS: a meta-analysis of randomized controlled trials
- The 40:1 myo-inositol/D-chiro-inositol plasma ratio is able to restore ovulation in PCOS patients: comparison with other ratios
- Inositol for subfertile women with polycystic ovary syndrome
- Inositol is an effective and safe treatment in polycystic ovary syndrome: a systematic review and meta-analysis of randomized controlled trials
Frequently Asked Questions
The most studied pattern is 4,000 mg myo-inositol per day combined with D-chiro-inositol at the 40:1 ratio — commonly taken as 2,000 mg myo plus 50 mg D-chiro twice daily. Myo-inositol alone is typically studied at 2 g twice daily.
A randomized trial comparing several myo-to-D-chiro ratios found 40:1 performed best for restoring ovulation in PCOS, and the systematic review behind the 2023 international guideline is built on 40:1-style protocols.
Most trials ran for roughly three to six months, so plan to judge the effect at that timeframe rather than after a few days. Evidence quality varies by outcome, and results are not guaranteed.
Some protocols use higher myo-inositol totals, but 4 g per day is the most common studied target for PCOS. Higher doses increase the chance of mild digestive side effects; the documented safety profile is built mainly on the standard range.