Can You Continue Metformin at eGFR 30–45?
At eGFR 30–45, metformin should be continued at a reduced dose (≤1000 mg/day) rather than stopped, per FDA 2016 relabeling. Do not initiate new therapy below eGFR 45. Discontinue entirely at eGFR <30 and hold temporarily around iodinated contrast or any acute illness that could impair renal perfusion.
Evidence review
Pivotal trials, effect sizes, and the populations they studied. PubMed identifiers link directly to the source.
Lazarus et al. observational cohort (2018)
PMID 2986884075,413 patients with eGFR 30–60 on metformin
No increased lactic acidosis risk at eGFR 30–60 with standard dosing; risk rose only at eGFR <30 (HR 2.07, 95% CI 1.33–3.22).
Practical decision algorithm
| If | Then |
|---|---|
| eGFR ≥45, new T2D | Initiate metformin 500 mg daily, titrate to 1000 mg BID over 2–4 weeks. |
| eGFR 30–44, already on metformin | Continue but cap at 1000 mg/day (500 BID or 1000 XR daily). Recheck eGFR every 3 months. |
| eGFR 30–44, not on metformin | Do not initiate. Prefer SGLT2 inhibitor or GLP-1 RA first. |
| eGFR <30 | Discontinue. Switch to SGLT2 (down to eGFR 20), GLP-1 RA, or insulin. |
| Scheduled iodinated contrast or acute illness | Hold metformin the day of contrast and 48 hours after; recheck creatinine before resuming. |
Guideline position
FDA 2016 label: metformin safe at eGFR ≥30, but not recommended to initiate at eGFR 30–45. ADA 2026 Standards of Care: continue reduced-dose metformin at eGFR 30–45; combine with SGLT2 inhibitor/GLP-1 RA for cardiorenal benefit.
Contraindications and cautions
- eGFR <30 mL/min/1.73 m2
- Acute/unstable heart failure with tissue hypoperfusion
- Hepatic failure or heavy alcohol use
- Acute illness with risk of dehydration (hold temporarily)
- Within 48 hours of iodinated contrast with eGFR <60