For women with PCOS and insulin resistance, the medication conversation increasingly comes down to two names: metformin, the decades-old workhorse, and the GLP-1 class led by semaglutide, the newer arrival reshaping metabolic medicine. Both target the insulin resistance at PCOS’s core; they get there very differently. Here is the honest head-to-head — including the fertility wrinkle that changes the calculus for many women.
Why Insulin Resistance Is the Battleground
Insulin resistance drives much of PCOS’s machinery: elevated insulin pushes the ovaries toward androgen production, disrupts ovulation, and promotes the weight gain that worsens the cycle further. Improve insulin sensitivity and the whole loop loosens — which is why both of these medications, neither designed for PCOS, earn their place in the conversation. Our PCOS and insulin resistance guide covers the mechanism in depth.
The Comparison
| Semaglutide (GLP-1) | Metformin | |
|---|---|---|
| How it works | Appetite reduction, slowed gastric emptying, improved insulin response | Reduces liver glucose output, improves insulin sensitivity |
| Weight effect | Substantial in trials (double digits percentage-wise at full doses) | Modest — typically a few pounds |
| PCOS-specific evidence | Growing but younger; studies show weight and metabolic improvements in PCOS populations | Decades of PCOS use; guideline-established, especially for cycle regularity and metabolic markers |
| Route and cost | Weekly injection (or oral daily); expensive, coverage varies for PCOS use | Cheap generic pills, decades of familiarity |
| Signature side effects | Nausea, GI effects during titration | GI upset, often improving with extended-release |
| The fertility wrinkle | Must be stopped well before conception; restored ovulation can arrive as a surprise | Long history of use in fertility contexts under provider guidance |
The Surprise-Ovulation Warning
This deserves its own heading because it catches women off guard: PCOS-related irregular ovulation is contraception for some women in practice, and effective weight loss on a GLP-1 can restore ovulation before anyone expects it. Combine that with the requirement to stop GLP-1s before pregnancy, and reliable contraception during treatment becomes non-negotiable unless pregnancy is the goal — in which case the sequencing conversation belongs with your provider before the first dose. Related reading: peptides and birth control.
How Clinicians Often Frame the Choice
Not as either/or. Metformin remains the guideline-familiar foundation — cheap, safe, decades of PCOS data. Semaglutide enters when weight is a major driver and metformin alone hasn’t moved it, and some women use both under supervision. Body composition matters during GLP-1 loss (see GLP-1s and muscle loss in women), and the supplement-tier comparison — including inositol, the best-evidenced non-prescription option — lives in myo-inositol vs peptides for PCOS. The full protocol picture: the PCOS peptide protocol.