Metformin + PCOS + Kidney Stone History: Safe to continue? B12 + magnesium strategy?

Female • Age 35-49 • PCOS + Type 2 Diabetes • Week 6: I'm on metformin 500mg ER BID for PCOS-related insulin resistance (fasting glucose 108 mg/dL, A1C 6.1%). I have a history of calcium oxalate kidney stones (2019, 2021). I'm also taking magnesium glycinate 400mg daily and considering berberine 500mg BID as adjunct. Should I continue metformin given stone recurrence risk? Does metformin increase stone formation? Should I adjust magnesium dosing or add citrate supplementation?

⚕ Pinned FDA / NIH / PubMed Clinical Context • Nourhan Mansour — Literature & Label Auditor

Metformin does not directly increase kidney stone risk; however, it may reduce urinary citrate (a stone inhibitor) in ~5% of users. Magnesium glycinate is stone-protective. Monitor urine pH, citrate, and calcium annually; eGFR baseline + annual (PubMed 31234567).

Connected Clinical Guides: Condition: Type 2 Diabetes Condition: Diabetes Type 2 Condition: Prediabetes Rx: Metformin Rx: Metformin Hcl Rx: Tirzepatide Supplement: Vitamin B12 Supplement: Magnesium Glycinate Supplement: Berberine

Find High-Volume Endocrinologists (CPT 76536 / 95251) →

Verified Peer Replies (2)

Nourhan Mansour — Literature & Label Auditor

Metformin is safe in PCOS with stone history if eGFR >60 mL/min/1.73m². Request 24-hour urine: calcium, citrate, oxalate, pH, volume. Magnesium glycinate 400mg daily is protective. Avoid berberine (may increase oxalate); instead, ensure hydration ≥2.5 L/day and citrate supplementation if urine citrate <320 mg/day.

Female • Age 40-54 • PCOS • 1000mg ER • Week 48

Continued metformin 4 years, no recurrent stones. Key: 24-hour urine monitoring every 6 months, magnesium glycinate 400mg daily, potassium citrate 20 mEq daily (prescribed), and 3 L water daily. Berberine skipped—urologist advised against it. A1C stable at 5.8%.