PCOS Supplements for Fertility: What to Take
Key Takeaways
- Myo-inositol, NAC and alpha-lipoic acid are the 3 supplements most often recommended for PCOS-related fertility support.
- Studied doses: myo-inositol 2,000 mg twice daily, NAC 1.2 to 3 g daily, alpha-lipoic acid 600 to 1,200 mg daily.
- Evidence is strongest for insulin sensitivity; effects on ovulation and pregnancy are less certain, and no guideline lists inositol as first-line.
- All 3 pause at the start of an FET cycle and restart if the transfer is unsuccessful.
- They’re taken on top of medical PCOS treatment such as letrozole or metformin.
For PCOS-related fertility support, the 3 supplements most commonly recommended are myo-inositol, NAC and alpha-lipoic acid. All 3 act on insulin resistance, which drives much of the ovulation disruption in PCOS, and they’re taken alongside medical treatment such as letrozole or metformin rather than in place of it.
At Markham Fertility Centre, supplement recommendations for PCOS patients are set by the care team as part of the treatment plan, alongside ovulation induction, IUI or IVF.
What Are the Best PCOS Supplements for Fertility?
The 3 supplements that come up most often for PCOS fertility support are myo-inositol, N-acetylcysteine (NAC) and alpha-lipoic acid (ALA). Each targets a different part of the problem.
- Myo-inositol targets insulin sensitivity and ovulation. It’s the most studied of the 3.
- NAC targets insulin sensitivity and oxidative stress. It’s an antioxidant precursor with insulin-sensitizing effects.
- Alpha-lipoic acid targets insulin sensitivity, and is often studied as a companion to myo-inositol.
Insulin resistance sits behind many of the ovulation problems in PCOS, which is why all 3 act on it. The medical side of that picture (letrozole, clomiphene, metformin, IUI, IVF) is covered in our article on PCOS treatment options.
Myo-inositol for PCOS: Dosage and Evidence
The most commonly studied dose is 2,000 mg of myo-inositol twice daily, for 4,000 mg a day, often paired with 200 mcg of folic acid per dose.
| Study | Dose and duration | Finding |
| Observational study of 3,602 infertile women with PCOS, 2018 | 2,000 mg myo-inositol + 200 mcg folic acid twice daily, 2 to 3 months | 70% of users restored ovulation and 15.1% became pregnant over a mean 10.2 weeks; a 29-patient IVF sub-study found better oocyte quality and more grade I embryos in the myo-inositol group |
| Systematic review for the 2023 International PCOS Guideline, 30 trials, 2,230 women | Myo-inositol or D-chiro-inositol, various doses | Benefits for some metabolic measures, a potential ovulation benefit from D-chiro-inositol, no clear effect on other outcomes |
The evidence is mixed. The observational study reported restored ovulation in most users and better oocyte and embryo quality in its small IVF sub-study, but it had no control group for the main cohort. The guideline review called the overall evidence limited and inconclusive, and the guideline doesn’t list inositol as a first-line treatment.
The same review found myo-inositol likely causes fewer gastrointestinal side effects than metformin, and those it does cause are typically mild.
Expert Insight
“Supplements can have a role in PCOS, particularly when insulin resistance is part of the picture, but I don’t want patients to think of them as a substitute for evidence-based fertility treatment. Myo-inositol, NAC and alpha-lipoic acid may support metabolic health, but the evidence for improving ovulation and pregnancy outcomes is less definitive. I use supplements as one part of an individualized treatment plan, alongside therapies such as letrozole or metformin when they’re indicated.”
— Dr. Meivys Garcia, Medical Director, Markham Fertility Centre
NAC for PCOS Fertility: Dosage and Evidence
NAC has been studied at 1.2 to 3 g a day, either as a continuous course over several weeks or as a 5-day course starting on day 3 of the cycle alongside an ovulation induction drug.
| Study | Dose and duration | Finding |
| First PCOS trial, Fertility and Sterility, 2002 | 1.8 g/day for 5 to 6 weeks (3 g/day for the heaviest participants) | Improved insulin sensitivity and lower testosterone in women with high baseline insulin |
| NAC with clomiphene, 180 women, 2012 | 1.2 g/day for 5 days from cycle day 3 | Higher ovulation and pregnancy rates than clomiphene plus placebo; no adverse effects reported |
| NAC with letrozole, 130 women, 2018 | 1.2 g/day for 5 days from cycle day 3 | Higher ovulation and pregnancy rates than letrozole plus placebo; no adverse effects reported |
| Meta-analysis of 18 studies, 2,185 women, British Journal of Nutrition, 2023 | Various | Lower total testosterone, higher FSH; no significant effect on follicle count or endometrial thickness |
| Meta-analysis of 8 randomized trials, 910 women, 2015 | Various | Higher odds of ovulation, pregnancy and live birth than placebo; lower odds than metformin |
NAC works as an antioxidant precursor and an insulin sensitizer, which is why it’s been tested both on its own and as an add-on to ovulation induction.
NAC is generally well tolerated. The 8-trial meta-analysis found no significant difference in adverse events between NAC and placebo. When side effects do occur, they’re usually mild and digestive (nausea, stomach upset).
Alpha-lipoic Acid for PCOS: Dosage and Evidence
Alpha-lipoic acid has been studied at 600 to 1,200 mg a day, and several trials pair it with myo-inositol.
| Study | Dose and duration | Finding |
| Trial in 6 lean, non-diabetic women with PCOS, 2010 | 600 mg twice daily for 16 weeks | 13.5% improvement in insulin sensitivity |
| Study of 71 women, 2020 | 800 mg ALA daily with 2,000 mg or 1,000 mg myo-inositol, 6 months | Improved cycle regularity in 71.2% of participants |
ALA improves insulin sensitivity through a pathway that doesn’t depend on insulin itself, which is the rationale for combining it with myo-inositol. In practice, it’s usually part of a combination.
When to Start and Stop These Supplements
The same rule applies to all 3: myo-inositol, NAC and alpha-lipoic acid stop when you start an FET cycle, and restart if the FET is unsuccessful and another transfer is planned.
- After an egg retrieval: keep taking them until your FET cycle begins, unless your care team says otherwise.
- During an active FET cycle: the focus shifts to preparing the uterine lining and supporting pregnancy, so egg-quality supplements are paused while prenatal vitamins, vitamin D and omega-3 continue.
- If your next step is another retrieval: stay on them if you’re tolerating them well. Egg development takes about 3 months, so the supplements need that window to matter.
| Supplement | Typical studied dose | What it targets | Stop and restart rule |
| Myo-inositol | 2,000 mg twice daily (4 g/day) | Insulin sensitivity, ovulation | Stop at start of FET cycle; restart if FET unsuccessful and another transfer is planned |
| NAC | 1.2 to 3 g daily | Insulin sensitivity, oxidative stress | Stop at start of FET cycle; restart if FET unsuccessful and another transfer is planned |
| Alpha-lipoic acid | 600 to 1,200 mg daily, usually with myo-inositol | Insulin sensitivity | Stop at start of FET cycle; restart if FET unsuccessful and another transfer is planned |
Choosing PCOS Supplements for Fertility: What the Research Supports
Myo-inositol, NAC and alpha-lipoic acid all have real clinical evidence behind them, and the studied doses are fairly consistent across trials: 2,000 mg of myo-inositol twice daily, 1.2 to 3 g of NAC, and 600 to 1,200 mg of alpha-lipoic acid.
What the research shows most clearly is an effect on insulin sensitivity, with a smaller and less certain effect on ovulation and pregnancy rates. Trials tested them alongside letrozole, clomiphene or metformin, and that’s how they’re used in practice: with medical treatment, stopped at the start of an FET cycle.
The same 3-month egg development window that applies to egg quality more broadly applies here, which is why they’re started well before a retrieval.
Which ones you take, and at what dose, is a decision for your fertility specialist, based on your diagnosis, your treatment plan and how you tolerate them.
Why Patients Choose Markham Fertility Centre
- PCOS assessment is built into the initial fertility evaluation, including hormonal, metabolic and ovarian reserve testing
- Personalized stimulation protocols for patients with PCOS, including modified natural cycle and antagonist protocols to reduce OHSS risk
- Coordination with broader specialist care when metabolic or endocrine management is needed alongside fertility treatment
- Five locations across Markham, Barrie-Innisfil, Oshawa, Orillia and Sudbury
- Ontario Fertility Program participant for funded IVF cycles
Book a consultation at Markham Fertility Centre →
FAQ
Can I take myo-inositol, NAC and alpha-lipoic acid with metformin or letrozole?
In several trials, they were taken alongside these medications. Tell your care team everything you’re taking so they can check for interactions and adjust doses.
How long before myo-inositol, NAC or alpha-lipoic acid has an effect?
Trials ran from 5 days (NAC with clomiphene) to 6 months. Because eggs take about 3 months to develop, starting at least 3 months before retrieval gives them time to matter.
Should I stop myo-inositol, NAC and alpha-lipoic acid before IVF?
No. Keep taking them through stimulation and retrieval. They stop when your FET cycle starts, and restart if that transfer is unsuccessful and another is planned.
Do I still need myo-inositol, NAC and alpha-lipoic acid if I already have frozen embryos?
Usually not during an active FET cycle, when the focus is your uterine lining. Restart them if the transfer fails and you’re planning another retrieval or transfer.
Do I need my doctor’s approval before starting myo-inositol, NAC or alpha-lipoic acid?
Yes. Doses, combinations and timing depend on your diagnosis and treatment plan. Your fertility specialist decides which of the 3 apply to you.
Sources
- Regidor PA et al. Management of women with PCOS using myo-inositol and folic acid. Hormone Molecular Biology and Clinical Investigation, 2018
- Fitz V et al. Inositol 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 and Metabolism, 2024
- Fulghesu AM et al. N-acetyl-cysteine treatment improves insulin sensitivity in women with polycystic ovary syndrome. Fertility and Sterility, 2002
- Salehpour S et al. N-acetylcysteine as an adjuvant to clomiphene citrate for successful induction of ovulation in infertile patients with polycystic ovary syndrome. Journal of Obstetrics and Gynaecology Research, 2012
- Mostajeran F et al. N-Acetylcysteine as an Adjuvant to Letrozole for Induction of Ovulation in Infertile Patients with Polycystic Ovary Syndrome. Advanced Biomedical Research, 2018
- Shahveghar Asl Z et al. The effects of N-acetylcysteine on ovulation and sex hormones profile in women with polycystic ovary syndrome: a systematic review and meta-analysis. British Journal of Nutrition, 2023
- Thakker D et al. N-Acetylcysteine for Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials. Obstetrics and Gynecology International, 2015
- Masharani U et al. Effects of controlled-release alpha lipoic acid in lean, nondiabetic patients with polycystic ovary syndrome. Journal of Diabetes Science and Technology, 2010
- Fruzzetti F et al. Clinical and Metabolic Effects of Alpha-Lipoic Acid Associated with Two Different Doses of Myo-Inositol in Women with Polycystic Ovary Syndrome. International Journal of Endocrinology, 2020
| Data | Article Section | Source |
| Myo-inositol, NAC and ALA are the 3 supplements recommended for PCOS | Key Takeaways, Intro, H2 #1 | Markham Fertility Supplement Quick Guide (Step 3, Quick Summary) |
| Myo-inositol 2,000 mg twice daily + 200 mcg folic acid, 2 to 3 months | Key Takeaways, Intro, Myo-inositol, Table | Regidor 2018, PubMed 29498933 |
| 3,602 women; 70% restored ovulation; 15.1% pregnancy; mean 10.2 weeks | Myo-inositol table | Regidor 2018, PubMed 29498933 |
| 29-patient IVF sub-study: better oocyte quality, more grade I embryos | Myo-inositol table | Regidor 2018, PubMed 29498933 |
| 30 trials, 2,230 women; metabolic benefit; DCI ovulation benefit; evidence limited and inconclusive | Myo-inositol table and text, Key Takeaways | Fitz 2024, PMC11099481 |
| Inositol not first-line in guideline | Key Takeaways, Myo-inositol | Fitz 2024, PMC11099481 |
| Myo-inositol fewer GI side effects than metformin, mild | Myo-inositol | Fitz 2024, PMC11099481 |
| NAC 1.2 to 3 g/day range | Key Takeaways, Intro, NAC, Table | Fulghesu 2002 (1.8 and 3 g), Salehpour 2012 and Mostajeran 2018 (1.2 g) |
| NAC 1.8 g/day, 5 to 6 weeks, 3 g for heaviest; improved insulin sensitivity, lower testosterone in hyperinsulinemic women | NAC table | Fulghesu 2002, PubMed 12057717 |
| NAC 1.2 g/day, 5 days from day 3 with clomiphene, 180 women; higher ovulation and pregnancy rates; no adverse effects | NAC table | Salehpour 2012, PubMed 22540635 |
| NAC 1.2 g/day, 5 days from day 3 with letrozole, 130 women; higher ovulation and pregnancy rates; no adverse effects | NAC table | Mostajeran 2018, PMC6036781 |
| 18 studies, 2,185 women; lower testosterone, higher FSH; no effect on follicles or lining | NAC table | Shahveghar Asl 2023, British Journal of Nutrition |
| 8 RCTs, 910 women; higher odds ovulation, pregnancy, live birth vs placebo; lower than metformin; no difference in adverse events | NAC table and text | Thakker 2015, PMC4306416 |
| NAC is an antioxidant (glutathione) precursor and insulin sensitizer | H2 #1, NAC | Viña 2025, PMC11768055 |
| NAC side effects usually mild and digestive | NAC | NAC trial protocols citing long-term oral NAC meta-analyses (clinicaltrials.gov NCT03055377, NCT04545008) |
| ALA 600 to 1,200 mg/day range | Key Takeaways, Intro, ALA, Table | Masharani 2010 (1,200), Fruzzetti 2020 (800), NCT07630779 (600) |
| ALA 600 mg twice daily, 16 weeks, 6 lean women; 13.5% insulin sensitivity improvement | ALA table | Masharani 2010, PubMed 20307398 |
| 800 mg ALA + 2,000 or 1,000 mg myo-inositol, 6 months, 71 women; 71.2% cycle regularity | ALA table | Fruzzetti 2020, PubMed 32256570 |
| ALA acts via an insulin-independent pathway (AMPK); rationale for combining with myo-inositol | H2 #1, ALA | Fruzzetti 2020, PubMed 32256570 |
| Insulin resistance drives anovulation in PCOS | H2 #1 | Viña 2025, PMC11768055; PMC13490353 |
| Stop at FET start; restart if FET unsuccessful and another transfer planned | Key Takeaways, Start/Stop, Table, FAQ 3 and 4 | Quick Guide (Step 4 table, FAQ) |
| Keep taking after retrieval until FET; pause during FET; prenatal, vitamin D, omega-3 continue | Start/Stop bullets, FAQ 4 | Quick Guide (FAQ) |
| Stay on them if planning another retrieval; egg development takes about 3 months | Start/Stop bullets, Closing, FAQ 2 | Quick Guide (FAQ) |
| Medical PCOS treatment: letrozole, clomiphene, metformin, IUI, IVF | Key Takeaways, Intro, H2 #1, Closing | markhamfertility.com/blog/pcos-treatment/ and /blog/pcos-renamed-to-pmos/ |
| Supplements set by care team based on diagnosis | Intro anchor | Quick Guide (Step 2, IVF row) |
| PCOS assessment in initial evaluation; OHSS-reducing protocols; specialist coordination; 5 locations; Ontario Fertility Program | Why Patients Choose | markhamfertility.com/blog/pcos-renamed-to-pmos/ |
| Dr. Meivys Garcia, Medical Director | Expert Insight placeholder | markhamfertility.com author page |