PCOS supplements that have evidence (and how strong it is)

The graded list

Inositol, the front-runner

Inositol in a 40:1 ratio has the best evidence of anything you can buy over the counter. Trials put it close to metformin on insulin and ovulation, and it is the only supplement the 2023 international guideline names.[1] It lowers fasting insulin and free testosterone and improves ovulation.[3] If you start with one thing, this is the one with the most behind it.

The moderate tier

NAC at 600mg twice daily has moderate evidence for lowering testosterone and improving ovulation. Omega-3 at around 2g of EPA and DHA a day has moderate evidence on inflammation, lipids, and insulin. Berberine, at 500mg two to three times a day, activates the same AMPK pathway as metformin and behaves much like it: a network meta-analysis found effects on insulin, glucose, lipids, and BMI.[2] Vitamin D helps insulin sensitivity, but mainly if you are actually deficient, so test first.

The lighter tier

Magnesium at around 400mg a day has weak-to-moderate evidence for insulin and sleep, and is low-risk. Spearmint tea at two cups a day has two small randomised trials showing lower free and total testosterone. These are worth having as habits, but do not expect either to be the thing that moves your PCOS on its own.

How to think about all of this

The population evidence for most of these is low-grade, and response varies a lot from person to person.[1] So do not treat any of them as a guarantee. Treat them as a test-and-track experiment: pick one, give it about 3 months, and retest the marker it is meant to move rather than going on how you feel. Do not stack five at once and hope.