Myo-Inositol for Fertility: Does It Help With PCOS?
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Myo-inositol is sold as a powder or capsule for PCOS, sometimes mixed with D-chiro-inositol. It is easy to buy and low risk, so it is worth knowing exactly what the evidence does and does not support. The short version: it is an acceptable option to discuss for PCOS, not a proven fertility treatment.
What is myo-inositol?
Inositol is a sugar alcohol. Myo-inositol and D-chiro-inositol are its two forms most studied in PCOS. Insulin resistance is common in PCOS, and inositol may have insulin-sensitizing effects, which is the reason it has been tested.2
In the US it is sold as a dietary supplement. By law, the FDA does not approve dietary supplements or their labeling.5 The PCOS guideline makes the same point: the regulation and quality control of inositol products can differ from those of medicines, and doses and quality may vary.1
What the 2023 PCOS guideline says about inositol
The 2023 International Evidence-based Guideline for PCOS, developed by an international network and published in several journals, has five statements on inositol.1 In plain words:
- Inositol, in any form, could be considered in PCOS based on your preferences and values. The guideline notes limited harm and potential improvement in metabolic measures, but limited clinical benefits, including in ovulation, hirsutism and weight.
- Metformin should be considered over inositol for hirsutism and central adiposity, although metformin has more stomach side effects.
- Specific types, doses or combinations cannot currently be recommended, because of a lack of quality evidence.
- Tell your healthcare professional if you take inositol or other complementary therapies.
- Decisions should include the fact that supplement regulation and quality differ from those of medicines.
For fertility specifically, the guideline names letrozole as the first-line medicine for ovulation induction in anovulatory women with PCOS who have no other infertility factors.1 Letrozole is a prescription drug, used off-label for this in many countries.
Myo-inositol: the evidence at a glance
| Claim | What the studies show | Evidence grade |
|---|---|---|
| Higher live birth before IVF (PCOS) | Uncertain: OR 2.42, 95% CI 0.75 to 7.83, 2 RCTs, 84 women3 | Very low |
| Fewer miscarriages (PCOS, IVF) | Effect disappeared when one outlier trial was removed3 | Very low |
| Better ovulation (PCOS) | Possible benefit from D-chiro-inositol; little or no effect on other outcomes2 | Low |
| Better metabolic markers (PCOS) | Some benefit for certain metabolic measures2 | Low |
| Fertility benefit without PCOS | No good trials found | Insufficient |
Does myo-inositol help with PCOS fertility?
It has not been shown to improve the outcomes that matter most. The 2018 Cochrane review included 13 trials and 1,472 women with PCOS, mostly using myo-inositol before IVF.3 The authors were uncertain whether it improves live birth (OR 2.42, 95% CI 0.75 to 7.83) or clinical pregnancy (OR 1.27, 95% CI 0.87 to 1.85).3 An apparent drop in miscarriage relied mainly on one trial with an unusually high control-group rate; without it, the effect disappeared.3 There was no pooled evidence for myo-inositol during ovulation induction.3
The 2024 meta-analysis commissioned for the guideline pooled 30 trials with 2,230 participants. It found benefits for some metabolic measures and possible benefits from D-chiro-inositol for ovulation, but likely no difference from metformin for reproductive outcomes. Myo-inositol likely caused fewer stomach side effects than metformin, which were usually mild.2 The authors called the evidence limited and inconclusive.2
Cochrane’s broader review of antioxidants for subfertile women, which includes myo-inositol trials, rated the overall evidence low to very low quality.4
In the Cochrane review, 11 of the 13 trials gave myo-inositol before IVF, and most were small. That is why the evidence grades are low even where results look positive.3
How much myo-inositol do people take?
The guideline’s answer is that no specific dose can be recommended.1 Products differ in dose and in the ratio of myo-inositol to D-chiro-inositol, and the evidence cannot tell those apart.12 If you decide to try it, choose one product, agree the dose with your doctor, and give it a defined trial period rather than taking it indefinitely.
Is myo-inositol safe?
The guideline describes limited harm.1 In the 2024 meta-analysis, myo-inositol caused fewer gastrointestinal side effects than metformin, and those were typically mild and self-limited.2 Because supplement quality varies, buy from a brand that publishes third-party testing.
Who might consider it, and what to do first
If you have PCOS and want a low-risk option for metabolic health, inositol is reasonable to discuss with your doctor. If you have PCOS and are not ovulating, it is not a substitute for medical care: ask about letrozole and an evaluation. Our guide to PCOS and getting pregnant covers treatment options, and irregular periods explains when cycles need checking.
To confirm whether you ovulate, LH tests can be tricky with PCOS; how to read an ovulation test explains the results. For supplements with inositol, check the label dose and look for third-party testing. And whatever else you take, the basics come first: folic acid, explained in methylfolate vs folic acid, and the rest of the Prepare hub.
Frequently asked questions
This page is educational and is not medical advice. Talk to a clinician about your own situation, and seek urgent care for heavy bleeding, severe pain or fainting.
Keep reading
PCOS and Getting Pregnant: What Works, Step by Step
How to get pregnant with PCOS: why ovulation is the issue, why the 2023 International PCOS Guideline makes letrozole first-line, and how to track cycles.
Irregular Periods and Trying to Conceive: What to Know
Irregular periods usually mean irregular ovulation. What counts as irregular, common causes, how to track ovulation, and why you can get evaluated now.
Methylfolate vs Folic Acid: Which Should You Take?
Methylfolate vs folic acid before pregnancy: CDC and USPSTF doses, what MTHFR variants really mean, ACMG advice on MTHFR testing, and how to read a prenatal label.
Step 1: Prepare for pregnancy
How to prepare for pregnancy: when to start a prenatal and folic acid, what a preconception checkup covers, and what the evidence says about supplements.
Sources
- 1Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Journal of Clinical Endocrinology & Metabolism. Teede HJ et al., 2023. Section 4.7 Inositol; letrozole as first-line ovulation induction
- 2Inositol for polycystic ovary syndrome: a systematic review and meta-analysis to inform the 2023 update of the international evidence-based PCOS guidelines. Journal of Clinical Endocrinology & Metabolism. Fitz V et al., 2024. 30 trials, 2,230 participants
- 3Inositol for subfertile women with polycystic ovary syndrome. Cochrane Database of Systematic Reviews. Showell MG et al., 2018. 13 trials, 1,472 women
- 4Antioxidants for female subfertility. Cochrane Database of Systematic Reviews. Showell MG et al., 2020. Includes myo-inositol trials
- 5Questions and answers on dietary supplements. U.S. Food and Drug Administration. FDA does not approve dietary supplements before they are marketed