Metformin XR 1000mg Dosing for Type 2 Diabetes
For metformin extended-release (XR) in type 2 diabetes, start at 500 mg once daily with the evening meal and titrate upward by 500 mg weekly until reaching the target dose of 2000 mg daily (maximum approved dose), adjusting based on renal function and tolerability. 1
Initial Dosing Strategy
- Start metformin XR at 500 mg once daily with the evening meal or dinner 1
- Titrate upward by 500 mg every 7 days as tolerated 1
- The maximum approved daily dose is 2000 mg for the extended-release formulation 1
- Most patients achieve adequate glycemic control at 1500-2000 mg daily 2
Dose Adjustments Based on Renal Function
Your dosing must be guided by estimated glomerular filtration rate (eGFR):
- eGFR ≥60 mL/min/1.73m²: Use full doses up to 2000 mg daily without adjustment 1
- eGFR 45-59 mL/min/1.73m²: Continue same dose but consider reduction if patient has comorbidities increasing lactic acidosis risk (heart failure, liver disease, sepsis) 1
- eGFR 30-44 mL/min/1.73m²: Reduce dose to maximum 1000 mg daily 1
- eGFR <30 mL/min/1.73m²: Stop metformin immediately—this is an absolute contraindication 1, 3
Monitoring Requirements
- Monitor eGFR at least annually in all patients on metformin 1
- Increase monitoring frequency to every 3-6 months when eGFR falls below 60 mL/min/1.73m² 1, 3
- Check vitamin B12 levels periodically, especially after 4 years of continuous use, as metformin causes biochemical B12 deficiency 1
- Monitor for signs of B12 deficiency (anemia, peripheral neuropathy) in long-term users 1, 4
Advantages of Extended-Release Formulation
- Once-daily dosing improves adherence compared to immediate-release metformin taken 2-3 times daily 5
- Better gastrointestinal tolerability due to slower absorption in the upper GI tract 5, 6
- Patients who cannot tolerate immediate-release metformin often tolerate the XR formulation 5
- Provides equivalent glycemic control (HbA1c reduction of 1-2 percentage points) to immediate-release at the same total daily dose 2, 5, 6
Common Pitfalls to Avoid
- Never continue metformin at any dose when eGFR drops below 30 mL/min/1.73m²—this is a hard stop due to lactic acidosis risk 1, 3
- Temporarily discontinue metformin before procedures with iodinated contrast, during hospitalizations, or when acute illness compromises renal/liver function 1
- Do not ignore GI side effects—if they occur, reduce the dose temporarily and re-titrate more slowly, or ensure the patient is taking XR formulation with food 4, 5
- The 1000 mg XR tablet strength exists, but starting at this dose without titration increases GI intolerance risk 1
Clinical Context
Metformin remains the first-line agent for type 2 diabetes regardless of formulation 1. The extended-release version at 1000 mg represents a mid-range therapeutic dose that many patients reach during titration. However, most patients require 1500-2000 mg daily for optimal glycemic control 2. If glycemic targets are not met at maximum metformin doses after 3 months, add a second agent—preferably an SGLT2 inhibitor (if eGFR ≥20-30) or GLP-1 receptor agonist for additional cardiovascular and renal benefits 1, 3.