Inositol (Myo-Inositol & D-Chiro-Inositol)
The insulin-sensitizing compound transforming PCOS management — with growing evidence for anxiety and mood
Also known as: Myo-Inositol • D-Chiro-Inositol • Vitamin B8 (unofficial) • MI • DCI
Overview
Inositol is a sugar alcohol that exists in nine isomeric forms, with myo-inositol (MI) and D-chiro-inositol (DCI) being the most biologically significant. Though sometimes called vitamin B8, it's not officially a vitamin because the body can synthesize it. Inositol is a second messenger in insulin signaling pathways, making it crucial for glucose metabolism and hormonal balance. It has become a cornerstone of PCOS (polycystic ovary syndrome) management, where it improves insulin sensitivity, restores ovulation, and reduces androgen levels. The optimal ratio of MI to DCI is 40:1, matching the body's natural ratio. Beyond PCOS, inositol shows promise for anxiety (at high doses of 12-18g), OCD, panic disorder, and metabolic syndrome.
Key Benefits
PCOS Management
Inositol is one of the most effective natural treatments for PCOS. Meta-analyses show myo-inositol improves insulin sensitivity, restores ovulation in 60-70% of anovulatory women, reduces testosterone levels, and improves egg quality. The 40:1 MI:DCI ratio is considered optimal for PCOS.
Insulin Sensitivity
Inositol is a key second messenger in insulin signaling. Supplementation improves insulin sensitivity in PCOS, metabolic syndrome, and gestational diabetes. Studies show reductions in fasting insulin, HOMA-IR, and glucose levels comparable to metformin in some populations.
Fertility & Egg Quality
Myo-inositol improves oocyte (egg) quality in women undergoing IVF. Studies show better fertilization rates, embryo quality, and pregnancy rates. It also restores spontaneous ovulation in anovulatory PCOS patients.
Anxiety & Mood
High-dose inositol (12-18g/day) has been studied for anxiety disorders, OCD, and panic disorder. It modulates serotonin and GABA receptor signaling. A study found 18g/day was as effective as fluvoxamine (an SSRI) for panic disorder with fewer side effects.
Gestational Diabetes Prevention
Myo-inositol supplementation during pregnancy (especially in women with PCOS or family history of diabetes) reduces the risk of gestational diabetes by 50-70% in clinical trials.
Dosage & How to Take
For PCOS: 2,000-4,000mg myo-inositol + 50-100mg D-chiro-inositol daily (40:1 ratio). For anxiety: 12,000-18,000mg myo-inositol daily. Start with lower doses and increase gradually.
| Purpose | Dose | Notes |
|---|---|---|
| PCOS (standard) | 4,000 mg MI + 100 mg DCI daily (40:1 ratio) | Divide into 2 doses. Results in 3-6 months. |
| Fertility/IVF support | 4,000 mg MI daily | Start 2-3 months before IVF cycle |
| Anxiety/OCD | 12,000-18,000 mg MI daily | High dose. Divide into 3 doses. Comparable to SSRIs in some studies. |
| Gestational diabetes prevention | 2,000-4,000 mg MI daily | Start in first trimester for at-risk women |
Best Time to Take
Divide into 2-3 doses throughout the day. Can be taken with or without food. Powder form mixes easily in water.
With or Without Food
Can be taken with or without food. No significant effect on absorption.
Forms & Bioavailability
| Form | Absorption | Best For | Notes |
|---|---|---|---|
| Myo-Inositol Powder | High | PCOS, flexible dosing | Slightly sweet taste. Mixes easily in water. Most cost-effective for high doses. |
| MI + DCI 40:1 Ratio Capsules | High | PCOS (optimal ratio) | Pre-combined in the physiological 40:1 ratio. Convenient but more expensive. |
| D-Chiro-Inositol Alone | High | Adding to existing MI supplementation | Only use in combination with MI. DCI alone at high doses may impair egg quality. |
Side Effects & Safety
Common
- Mild GI upset (nausea, gas, diarrhea) at high doses
- Headache when starting
Rare
- Insomnia at very high doses
- Dizziness
Contraindications
- D-chiro-inositol alone at high doses may impair egg quality — always combine with myo-inositol
- Bipolar disorder (high-dose inositol may trigger mania — theoretical concern)
Interactions
Inositol and metformin have similar mechanisms; may have additive insulin-sensitizing effects. Some doctors use both together for PCOS.
Inositol affects serotonin signaling; may have additive effects with antidepressants. Monitor for serotonin-related side effects.
Lithium depletes inositol; this may be part of lithium's mechanism of action. Supplementation may reduce lithium efficacy.
Scientific Research
Inositol for PCOS Meta-Analysis
Myo-inositol restored ovulation in 60-70% of anovulatory PCOS women and improved insulin sensitivity comparable to metformin
Inositol vs Fluvoxamine for Panic Disorder
18g/day myo-inositol was as effective as 150mg/day fluvoxamine for panic disorder with fewer side effects
Inositol and Gestational Diabetes
4,000mg MI daily from first trimester reduced gestational diabetes incidence by 65% in at-risk women
Food Sources
Frequently Asked Questions
Medical Disclaimer
This content is for educational and informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional before starting any supplement regimen, especially if you have pre-existing health conditions or are taking medications. The statements on this page have not been evaluated by the Food and Drug Administration.