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Supplements for PCOS: What Inositol and the Others Can and Can't Do

For PCOS (polycystic ovary syndrome), lifestyle change and prescribed medicines come first, and no supplement replaces them. Inositol has the most trials (grade B): it made periods more regular and improved insulin tests, but the review behind the 2023 international guideline called the evidence limited and inconclusive. Berberine lowered testosterone in one placebo trial (grade C), without more live births, and it slows enzymes that clear many medicines, so ask your pharmacist first.

Published Updated How we grade evidenceEditorial policy

The short version

  • Lifestyle change (diet, activity, behavior support) lowered weight and a testosterone measure a little in small trials, and the international guideline emphasizes it. Grade B (Lim 2019; Teede 2023).
  • Inositol made periods more regular and improved insulin tests, but the guideline's own review called the evidence limited and inconclusive. Grade B (Fitz 2024; Greff 2023).
  • The 40:1 myo-inositol to D-chiro-inositol mix rests on one trial with 8 women per group. Grade D (Nordio 2019).
  • Berberine lowered testosterone in the review's one placebo trial of berberine alone; the other 7 testosterone trials added it to another PCOS treatment, and live births were no higher than on placebo or metformin. Grade C (Xie 2019; An 2014).
  • NAC, vitamin D, omega-3, chromium and CoQ10 nudged blood sugar, insulin or blood fats in pooled trials. Grade B (Liu 2023; Yin 2024; Huang 2023; Hamsho 2025; Zhang 2023).
  • Spearmint tea and cinnamon: small trials only. Grade C (Grant 2010; Heydarpour 2020).

What does the PCOS guideline recommend first?

Healthy lifestyle is its main emphasis, medicines are chosen with your clinician, and supplements come after. PCOS affects about one in eight women, and in 2026 an international consensus proposed renaming it polyendocrine metabolic ovarian syndrome, PMOS, to reflect its hormone and metabolic effects (Teede 2026). The 2023 international guideline keeps its emphasis on healthy lifestyle and wellbeing, and rates most of its evidence low to moderate in quality (Teede 2023).

Grade B for lifestyle change. In a Cochrane review, lifestyle programs lowered weight 1.68 kg (9 trials, 353 women) and the free androgen index, a testosterone measure (6 trials, 204 women), on low-quality evidence; no trial reported regular periods or live births (Lim 2019). Clinicians may prescribe the pill to regulate periods and ease hair growth and acne, or metformin, a diabetes medicine (MedlinePlus). Those are your prescriber's call. A 2025 network analysis of supplement trials (79 trials, 5,501 women) tracked blood tests, not symptoms, and no supplement beat placebo on total testosterone (Zhao 2025). Our graded findings are on the PCOS page and PCOS protocol.

SupplementWhat trials foundSize of the evidenceGrade
InositolMore regular periods; better insulin testsGuideline review: limited, inconclusiveB
40:1 inositol mixBest of 7 ratios for ovulation1 trial, 56 womenD
BerberineLower testosterone in 1 placebo trial; no more live births12 trials; 7 of the 8 testosterone trials added it to another treatmentC
NACSlightly lower fasting blood sugar11 trialsB
Vitamin DSmall drops in blood fats15 reviewsB
Omega-3Lower blood fats and insulin resistance7 trialsB
ChromiumLower insulin and blood fats10 trialsB
CoQ10Better insulin resistance9 trialsB
CinnamonLower fasting blood sugar5 trialsC
Spearmint teaLower testosterone; hair scores unchanged1 trialC
MagnesiumNo clear effect6 trialsB

Does inositol help PCOS?

Grade B, for more regular periods and better insulin tests. The review written for the 2023 guideline included 30 trials (2,230 women). Either form of inositol improved a few metabolic measures, and D-chiro-inositol may aid ovulation, but the authors called the evidence "limited and inconclusive" (Fitz 2024). In another review's pooled placebo-controlled trials, women on inositol were 1.79 times as likely to have regular cycles (Greff 2023). Its list of included trials has one that was retracted in 2023 as a duplicate of an earlier paper (retraction notice).

Trials in adults outside pregnancy used, for example, 4 g of myo-inositol a day for 6 months, or 2 g of inositols twice a day for 3 months (Fruzzetti 2017; Nordio 2019). If you are trying to get pregnant, talk to your clinician: a Cochrane review of 13 trials in women having fertility treatment rated the evidence low to very low quality (Showell 2018). Our inositol page calls the PCOS evidence strong; this guide's grade B reflects the guideline review, which did not find it convincing.

Myo-inositol or D-chiro-inositol: is 40:1 best?

Grade D for the 40:1 claim. It comes from one trial of 56 women, 8 per group, that compared 7 ratios of the two forms for 3 months and found 40:1 best for restoring ovulation (Nordio 2019). A 2026 umbrella review found myo-inositol did best for metabolic and reproductive measures, combinations did not consistently beat a single form, and D-chiro-inositol alone should be used with caution (Duan 2026).

Inositol vs metformin: which works better?

Grade B for no clear difference in blood tests. A review of 8 trials (1,088 women) found that myo-inositol and metformin did not differ for weight, fasting insulin, blood sugar or insulin resistance (Fatima 2023). The guideline review found metformin may do better for waist-to-hip ratio and unwanted hair, while myo-inositol likely causes fewer stomach side effects, which were mild (Fitz 2024). Adding inositol to metformin made periods more regular and lowered hair-growth scores in 6 trials (388 women) over 3 to 6 months (Kelly 2025). A supplement is not a replacement for a prescribed medicine; ask your prescriber.

Does berberine help PCOS?

Grade C for lower testosterone, not for babies. A review of 12 trials found total testosterone slightly lower with berberine in the 8 trials (577 women) that measured it, but 7 of them added berberine to another PCOS treatment (mostly a cyproterone hormone pill, metformin or a herbal medicine) and compared it with that treatment alone, and results varied widely (Xie 2019). In the one that tested berberine alone against placebo, in 150 women preparing for IVF, testosterone fell more on berberine than on placebo over 3 months (An 2014). In the review, live births did not differ from placebo or metformin, and were fewer than with the fertility drug letrozole. Against metformin, it lowered total cholesterol (3 trials, 201 women) and waist size, and it caused no extra stomach side effects compared with placebo (Xie 2019). On metformin? Read can I take berberine with metformin? and ask your prescriber or pharmacist.

Does NAC help PCOS?

Grade B for a small drop in fasting blood sugar; the hormone results are uncertain. In a 2023 review of 11 trials (869 women in all), N-acetylcysteine (NAC) lowered fasting blood sugar compared with metformin and with placebo, and total cholesterol compared with placebo (Liu 2023). Two reviews of NAC and hormones disagree, and both pooled several trials that have since been retracted, so those results are uncertain (Shahveghar Asl 2023; Viña 2025).

Should you take vitamin D for PCOS?

Grade B, for small drops in blood fats. An umbrella review of 15 meta-analyses found vitamin D lowered triglycerides, total and LDL cholesterol and total testosterone a little, with no change in insulin, HDL or weight (Yin 2024). A review of 12 studies (849 women) found more regular cycles, but in its subgroup analyses the effect held only above 4,000 IU a day, after more than 8 weeks, or with other supplements alongside (Han 2023). Our database grades the blood fat effect A; this guide gives B because the changes are small and the umbrella review calls earlier results inconsistent. Upper limit for adults: 4,000 IU a day, because more can raise blood calcium; take more only with blood tests or your clinician's advice (NIH ODS; check your stack).

What about omega-3, chromium, CoQ10 and cinnamon?

They changed blood tests in small trials; none was shown to change symptoms.

  • Omega-3: a review of 7 studies (574 women) found lower total cholesterol, triglycerides, insulin resistance and testosterone, but no change in unwanted hair. Grade B (Huang 2023).
  • Chromium: in a review of 10 trials (683 women), chromium picolinate (the review points to 200 mcg a day) lowered fasting insulin and blood fats against placebo. Grade B (Hamsho 2025).
  • Coenzyme Q10: a review of 9 trials (1,021 women) found better insulin resistance, testosterone and blood fats; only one trial reported on side effects, and it found none. Grade B (Zhang 2023). Our PCOS page shows C from studies that were not in PCOS.
  • Cinnamon: 5 trials found lower fasting blood sugar and insulin, with no weight change (Heydarpour 2020); in one trial of 45 women, 1.5 g a day made periods more frequent, but only 17 finished 6 months (Kort 2014). Grade C.

Does spearmint tea help hirsutism?

Grade C. In 42 women with PCOS, spearmint tea twice a day for 30 days lowered free and total testosterone and women rated their unwanted hair as better, but the doctor-scored hair rating did not change (Grant 2010). Hair grows slowly, so a month may be too short to tell.

What we'd skip

  • Magnesium for PCOS. A 2025 meta-analysis of 6 trials found no effect on hormones or heart and metabolic risk factors (Abu-Zaid 2025).
  • D-chiro-inositol on its own, which the 2026 umbrella review says to use with caution (Duan 2026).
  • Any supplement as a stand-in for a prescribed medicine. The head-to-head trials mostly compared blood tests, not long-term health (Fatima 2023).

Safety and interactions

  • Berberine: in healthy men, 2 weeks of 300 mg three times a day reduced the activity of three liver enzymes that clear many drugs (CYP2D6, CYP2C9 and CYP3A4) and raised a test drug's levels 40% (Guo 2012). NCCIH warns that berberine can harm newborns; if you are pregnant or breastfeeding, ask your doctor or midwife (NCCIH).
  • Blood sugar: inositol, NAC, chromium, CoQ10 and cinnamon lowered blood sugar or insulin in the trials above, and berberine adds to metformin's effect (berberine and metformin); with metformin or insulin, check readings as your prescriber advises.
  • Inositol: stomach side effects were fewer than on metformin, and mild (Fitz 2024). If you take metformin or other diabetes medicines, ask your pharmacist before adding it.
  • Chromium: no upper limit has been set, but people with kidney or liver disease may be more likely to have side effects (NIH ODS).
  • Cinnamon: cassia cinnamon contains coumarin, which has been linked to liver problems, so take care with liver disease (NCCIH).
  • Stacks: taking several? Check your stack against the upper limits.

When to see a doctor

  • See a clinician to confirm PCOS if you have irregular or missing periods, unwanted hair or trouble getting pregnant (MedlinePlus).
  • Ask about screening. The guideline flags higher metabolic and heart risks, sleep apnea, very common mental health problems, and higher pregnancy risks in PCOS (Teede 2023).
  • Trying to conceive? Plan supplements with your fertility clinician; see our infertility page.
  • Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. If you are pregnant, breastfeeding or under 18, ask a clinician (your doctor or midwife) first.

FAQ

Does inositol help PCOS? A little (grade B): pooled trials found more regular periods and better insulin tests. The review written for the 2023 international guideline still called the evidence limited and inconclusive.

How much inositol do PCOS trials use? Trials in adults outside pregnancy used, for example, 4 g of myo-inositol a day for 6 months, or 2 g of inositols twice a day for 3 months. Pregnant or hoping to conceive? Ask your clinician.

Is the 40:1 myo-inositol to D-chiro-inositol ratio best? That claim rests on one trial with 8 women per group (grade D). A 2026 umbrella review found combinations did not consistently beat myo-inositol alone.

Is inositol better than metformin? In 8 trials, blood tests did not differ between the two. Metformin may do better for waist-to-hip ratio and unwanted hair, and myo-inositol caused fewer stomach side effects; the choice is your prescriber's.

Can I take berberine with metformin? Ask your prescriber or pharmacist first: both lower blood sugar, and berberine slows enzymes that clear many medicines.

Sources

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