Myo-inositol at 4 grams per day is a metabolic tool in insulin-resistant adults, especially women with polycystic ovary syndrome or metabolic syndrome: trials show lower insulin resistance, triglycerides, and plaque-linked cholesterol. Cycle regularity is contested. It is not a settled fertility drug or a general aging supplement. Limits are nausea at high dose and extra glucose lowering with diabetes drugs. (Full Review)

Protocol

Metabolic / PCOS default

2 g twice daily

4 g/day myo-inositol, often with 200–400 µg folate, for at least 8–12 weeks

Time of day

Breakfast and dinner

Split metabolic doses; adult oral absorption saturates above about 2 g

40:1 combination

550–1,100 mg twice daily

Myo-inositol plus D-chiro-inositol at 40:1; independent confirmation is limited

Time to effect

Insulin and HOMA-IR

8 weeks

Most metabolic trials; some ran 6 months

Sperm count and motility

3 months

Idiopathic male infertility trial duration

Sleep

Same night to a few days

Evening-dose anecdotes; one pregnancy trial used 10 weeks

Benefits

High: Lower triglycerides and low-density lipoprotein cholesterol; lower incidence of gestational diabetes; lower blood pressure

Medium: Improved insulin resistance; lower androgens in insulin-resistant PCOS; reduction in body mass index; improvement of lithium-associated psoriasis; better sleep scores in pregnancy; lower liver fat in non-alcoholic fatty liver disease; improved sperm count and motility

Low: More regular menstrual cycles in PCOS; fewer panic attacks at high dose; lower thyroid antibodies when combined with selenium

Speculative: Healthspan gain in insulin-sensitive adults; protection against Alzheimer disease

Contraindications

Recurrent hypoglycemia on insulin or sulfonylureas when glucose cannot be monitored after adding a sensitizer

High-dose D-chiro-inositol monotherapy as a fertility intervention

12–18 g/day plus lithium for mood stability

Bipolar disorder at 12–18 g/day without specialist follow-up

IP6 (phytic acid) products in place of myo-inositol if at risk of iron or zinc deficiency

Key Interactions

Metformin (caution)

Insulin and sulfonylureas (glipizide, glyburide) (caution)

SGLT2 inhibitors (empagliflozin, dapagliflozin) and GLP-1 receptor agonists (semaglutide, liraglutide) (monitor)

Berberine, N-acetylcysteine, and alpha-lipoic acid (caution)

Antihypertensives (lisinopril, amlodipine) (monitor)

Lithium (caution at high dose)

Valproate (caution, limited data)

SSRIs (fluvoxamine, sertraline) (monitor)

Selenium (additive in thyroid protocols)

IP6 / phytate products (caution if mislabeled as inositol)

Risk & Side Effects

High: Gastrointestinal symptoms at high dose

Low: High-dose D-chiro-inositol and oocyte quality; additive blood-glucose lowering; theoretical blunting of lithium’s central effect; headache, dizziness, and tiredness; mania or hypomania in bipolar disorder

Speculative: Mineral binding from inositol hexaphosphate

Monitoring

Marker	Target	Why
Fasting insulin	3–8 µU/mL	Confirms insulin-resistance target
HOMA-IR	<1.0–1.5	Tracks the primary metabolic effect
Fasting glucose	75–90 mg/dL	Safety and insulin-resistance context
Triglycerides	<100 mg/dL	Captures the lipid signal
LDL cholesterol	Individualized; many functional clinics use <100 mg/dL	Captures LDL change in the trial pool
HbA1c	4.8–5.3% if used	Longer glycemic context
Total / free testosterone (women with PCOS)	Toward the laboratory female reference, interpreted with SHBG	Tracks androgen response
TSH	0.5–2.5 mIU/L if thyroid autoimmunity is the target	Only if using the selenium-combination literature

Cadence: Baseline fasting insulin, glucose, and lipids (androgens and cycle log in PCOS); repeat the blood panel at 8–12 weeks, then every 6–12 months if continued; home glucose for 2–4 weeks if on insulin or sulfonylureas

Qualitative Assessment

Menstrual cycle length and ovulation signs (if PCOS is the target)
Gastrointestinal tolerance (stool frequency, nausea)
Sleep continuity and time to return to sleep
Panic-attack frequency (only if a high-dose protocol is in use)
Energy and post-meal glucose symptoms
Home glucose if on insulin or sulfonylureas

Inositol for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment