Inositol Dosage Calculator — Myo + D-chiro for PCOS / PMOS
Inositol is one of the best-studied supplements for PCOS / PMOS. Two forms are used clinically: myo-inositol (MI) and D-chiro-inositol (DCI). The optimal dosage and ratio depend on your primary goal — insulin resistance, fertility, cycle regularisation, or hyperandrogenism.
This calculator provides a protocol based on published clinical evidence, including the landmark work of Nestler et al. (2001), Unfer et al. (2012), and Papaleo et al. (2007). For a detailed comparison of approaches, see our inositol vs metformin guide.
Calculate my inositol protocol
Used to flag a dosage note if your weight exceeds 90 kg.
What is inositol and why is it used in PCOS?
Inositol is a cyclic sugar-like molecule found naturally in many foods (citrus fruits, legumes, whole grains) and synthesised by the body from glucose. It acts as a second messenger in cellular insulin signalling.
In PCOS, abnormalities in inositol metabolism have been described since the 1990s: a deficit in myo-inositol in certain tissues (ovarian, muscular) contributes to insulin resistance. Supplementation aims to correct this imbalance through a nutritional pathway.
Myo-inositol (MI) is the predominant form in human plasma (95–99% of circulating inositol). It acts primarily on FSH signalling and oocyte maturation. D-chiro-inositol (DCI), present at much lower levels, is a mediator of insulin action in muscles and the liver — it plays a role in reducing ovarian androgen production.
The physiological human plasma ratio is approximately 40:1 (MI:DCI), first described by Nestler et al. in 2001. This ratio is used in the majority of clinical protocols for non-specific PCOS. Variations exist depending on the primary therapeutic goal.
Choosing your protocol: goal by goal
Insulin resistance
When insulin resistance is the primary concern (elevated HOMA-IR, borderline fasting glucose, high triglycerides, central adiposity), most protocols use 4 g/day of myo-inositol with an increased D-chiro-inositol dose of 200 mg (a 20:1 ratio). This higher DCI ratio enhances insulin sensitivity in muscle cells. Always inform your doctor if you are also taking metformin, as an additive effect may require monitoring.
Fertility and oocyte quality
For fertility, multiple studies (Papaleo et al., 2007; Unfer et al., 2012) show that myo-inositol alone at 4 g/day improves oocyte quality, nuclear maturity of eggs, and fertilisation rates in IVF. Excess D-chiro-inositol can paradoxically impair oocyte quality by reducing FSH responsiveness in granulosa cells. In a fertility context, myo-inositol alone is often preferred.
Irregular cycles
For cycle regularisation, the 40:1 ratio (4 g MI + 100 mg DCI) is the most studied and widely used protocol. It corresponds to the combined supplements available in pharmacies (Inofolic, Ovaric HP, etc.). Studies show improvement in cycle regularity in 65–75% of patients after 3–6 months of continuous use.
Hyperandrogenism (acne, hirsutism)
D-chiro-inositol reduces ovarian androgen production by improving insulin sensitivity in thecal cells. The 40:1 ratio is generally used for hyperandrogenism. Effects on acne and hirsutism are progressive and less predictable than with spironolactone — combination may be considered by your doctor as part of comprehensive PCOS management.
Interpreting results and practical recommendations
Regardless of the chosen protocol, inositol should ideally be taken in 2 daily doses before meals (morning and evening). This approach improves absorption and maintains stable levels over 24 hours. Powdered forms dissolved in water are better absorbed than tablets.
Side effects are rare and mild: slight gastrointestinal discomfort when starting, which typically resolves within 1–2 weeks. If digestive symptoms persist, a temporary dose reduction is possible before gradually resuming.
A blood panel at 3 months (fasting insulin, glucose, free testosterone, hormonal profile) allows measurement of protocol efficacy and adjustment if needed. A complete clinical assessment at 6 months is recommended.
Interaction with metformin: Inositol and metformin act on different but complementary pathways. A potentiation of the blood-glucose-lowering effect is possible. Alert your doctor when starting inositol if you take metformin — blood sugar monitoring may be indicated initially.
Research evidence and clinical references
Evidence on inositol in PCOS has been accumulating since the early 2000s, with several meta-analyses and randomised controlled trials (RCTs) providing moderate to robust evidence for certain parameters.
- Nestler JE et al. (2001) — Ovulatory and metabolic effects of D-chiro-inositol in the polycystic ovary syndrome. New England Journal of Medicine. Foundational reference establishing the 40:1 ratio.
- Papaleo E et al. (2007) — Myo-inositol in patients with polycystic ovary syndrome: a novel method for ovulation induction. Gynecological Endocrinology. Myo-inositol alone for fertility.
- Unfer V et al. (2012) — Effects of myo-inositol in women with PCOS: a systematic review of randomized controlled trials. Gynecological Endocrinology. Meta-analysis confirming efficacy of the 40:1 ratio.
- Genazzani AD et al. (2014) — Myo-inositol administration positively affects hyperinsulinemia and hormonal parameters in overweight patients with PCOS. Gynecological Endocrinology. Comparison with metformin.
- Dinicola S et al. (2021) — Myo-inositol as a key supporter of fertility and physiological gestation. Pharmaceuticals. Updated review on pregnancy outcomes.
Practical tips for getting started
- Choose a powder form dissolved in water rather than capsules for better bioavailability.
- Take inositol before meals (morning and evening), ideally on an empty stomach or at least 20 minutes before eating.
- Start at half the dose for the first 2 weeks if you are prone to digestive sensitivity.
- Note your start date and request a blood panel at 3 months to track changes in your markers (fasting glucose, insulin, free testosterone).
- Ensure the supplement you buy is GMP-certified (Good Manufacturing Practice) and contains no unnecessary additives.
- Inositol does not replace a prescribed treatment — never stop any medication without your doctor's agreement.
Frequently asked questions
What is the difference between myo-inositol and D-chiro-inositol?
Myo-inositol (MI) is the predominant form in the human body (95–99% of total inositol). It plays a key role in insulin signalling and oocyte maturation. D-chiro-inositol (DCI) is a mediator of insulin action in muscle and liver cells. In human plasma, the MI:DCI ratio is approximately 40:1. Research shows women with PCOS often have a tissue deficit in MI and a relative excess of DCI.
Why is the 40:1 ratio recommended for PCOS?
The 40:1 ratio corresponds to the physiological ratio in human plasma (Nestler et al., 2001). Studies confirm this ratio outperforms different ratios or either form alone for improving PCOS parameters. Excess DCI beyond this ratio can reduce oocyte quality, which is why fertility protocols sometimes prefer myo-inositol alone.
How long does inositol take to work for PCOS?
Early improvements may appear after 1–2 months. Effects on oocyte quality, testosterone, and complete cycle regularisation generally require 3–6 months of continuous use. A review with your doctor at 3 months allows protocol confirmation or adjustment.
Can inositol replace metformin for PCOS?
Inositol is not a medication and does not replace prescribed metformin. Comparative studies suggest comparable metabolic efficacy at 4 g/day with fewer GI side effects, but this decision belongs to your doctor based on your individual lab results.
Is inositol safe to take during pregnancy?
At PCOS doses (4 g/day myo-inositol), inositol is not considered teratogenic. Studies are evaluating its role in preventing gestational diabetes. Continuing during pregnancy should be discussed with your doctor or midwife.