With an estimated glomerular filtration rate of 44 mL/min/1.73 m², type 2 diabetes (hemoglobin A1c 8.2%) on metformin 500 mg twice daily, losartan 100 mg plus hydrochlorothiazide 25 mg, and furosemide 40 mg daily, can I increase the metformin dose or add another glucose‑lowering agent, and should I adjust the furosemide dose?

Management of Diabetes and Diuretics at eGFR 44 mL/min/1.73 m²

Continue metformin 500 mg twice daily without dose reduction, add an SGLT2 inhibitor (canagliflozin or dapagliflozin) regardless of glucose control for kidney and cardiovascular protection, and continue furosemide 40 mg daily with electrolyte monitoring every 3–6 months. 1, 2

Metformin Management at eGFR 44 mL/min/1.73 m²

Your current metformin dose of 500 mg twice daily (1000 mg total) is safe and should be continued without reduction at eGFR 44 mL/min/1.73 m². 1, 2, 3

Current Dosing Strategy

• At eGFR 44 mL/min/1.73 m², you fall within the FDA-approved range (30–44 mL/min/1.73 m²) where metformin can be continued but requires careful reassessment of the benefit-risk balance. 1, 2
• The 2016 FDA guidance explicitly states metformin should not be initiated at eGFR 30–44 mL/min/1.73 m², but patients already taking it may continue with dose reduction consideration. 1, 3
• Since you are taking only 1000 mg daily (well below the maximum 2000–2550 mg), no immediate dose reduction is required unless additional risk factors exist (advanced age, liver disease, alcoholism, heart failure, or volume depletion risk). 2, 4

Critical Monitoring Requirements

• Increase eGFR monitoring frequency to every 3–6 months (not annually) because your kidney function is below 60 mL/min/1.73 m². 1, 2, 4
• Monitor vitamin B12 levels if you have been on metformin for more than 4 years, as approximately 7% develop deficiency. 2, 4
• Check electrolytes every 3–6 months given your eGFR is in stage 3b CKD. 1

Future Thresholds You Must Know

• If eGFR remains 30–44 mL/min/1.73 m²: Continue current dose (1000 mg daily) with close monitoring. Some guidelines suggest reducing to maximum 1000 mg daily in this range, which you are already at. 2, 3, 4
• If eGFR falls below 30 mL/min/1.73 m²: Discontinue metformin immediately due to unacceptable risk of fatal lactic acidosis. 1, 2, 3
• If eGFR improves to 45–59 mL/min/1.73 m²: You could safely increase metformin dose if needed for glucose control, up to 2000 mg daily. 2, 3

When to Stop Metformin Temporarily

• Hold metformin immediately during acute illness causing volume depletion (sepsis, severe diarrhea, vomiting, dehydration). 2, 3
• Stop metformin before iodinated contrast imaging procedures given your eGFR is in the 30–60 range, especially with your history of heart failure (on furosemide). 1, 2
• Re-check eGFR 48 hours after contrast procedures before restarting metformin. 2, 3

Adding Glucose-Lowering Agents: SGLT2 Inhibitors Are Essential

Add an SGLT2 inhibitor (canagliflozin or dapagliflozin) to your current regimen immediately, regardless of your A1c level, because these agents slow CKD progression and reduce cardiovascular events independent of glucose control. 1, 2

Why SGLT2 Inhibitors Are Mandatory at Your eGFR

• The American Diabetes Association strongly recommends SGLT2 inhibitors at eGFR ≥30 mL/min/1.73 m² for patients with type 2 diabetes and CKD (which you have at eGFR 44). 1, 2
• At eGFR 44 mL/min/1.73 m², you are well above the threshold for starting these medications. 1, 2
• SGLT2 inhibitors reduce risk of CKD progression by 39–40%, reduce cardiovascular events, and reduce heart failure hospitalizations—benefits that occur regardless of glucose lowering. 1

Specific Agent Selection

• Canagliflozin or dapagliflozin are preferred because they have the strongest evidence for kidney protection at your eGFR level. 1, 2
• Empagliflozin is also acceptable but has slightly less robust kidney-specific data. 1
• These agents can be used down to eGFR 20 mL/min/1.73 m² for kidney and cardiovascular protection, even though glucose-lowering effects diminish below eGFR 30–45. 1, 2

Expected Initial eGFR Dip

• Expect an initial eGFR decline of 3–5 mL/min/1.73 m² within the first few weeks of starting an SGLT2 inhibitor—this is normal and beneficial. 1
• This "eGFR dip" represents hemodynamic changes that protect the kidney long-term; kidney function typically returns toward baseline within weeks and remains stable thereafter. 1
• Do not stop the SGLT2 inhibitor due to this initial dip unless eGFR falls below 20 mL/min/1.73 m². 1

Addressing Your A1c of 8.2%

• Your A1c is above target (typically <7–7.5% for most patients), so adding an SGLT2 inhibitor serves dual purposes: kidney/cardiovascular protection and improved glucose control. 1, 2
• The SGLT2 inhibitor will likely lower your A1c by 0.5–1.0%, bringing you closer to target. 1

Alternative or Additional Glucose-Lowering Agents

GLP-1 Receptor Agonists

• If you cannot tolerate or afford an SGLT2 inhibitor, a GLP-1 receptor agonist (dulaglutide, liraglutide, or semaglutide) is the next best option. 1, 2
• GLP-1 RAs reduce cardiovascular events by 22–36% and appear to slow CKD progression, though the kidney benefits are less robust than SGLT2 inhibitors. 1
• These agents require no dose adjustment at eGFR 44 mL/min/1.73 m² and can be used down to eGFR <20 mL/min/1.73 m². 1, 2
• Weekly options (dulaglutide, semaglutide) are more convenient than daily liraglutide. 1

Combining SGLT2 Inhibitors and GLP-1 RAs

• Ideally, you should be on both an SGLT2 inhibitor and a GLP-1 RA given your A1c of 8.2%, eGFR 44, and cardiovascular risk factors. 1
• This combination provides additive kidney protection, cardiovascular benefits, and glucose lowering without significant hypoglycemia risk. 1

Do NOT Increase Metformin Dose

• Given your eGFR of 44 mL/min/1.73 m², you should not increase metformin beyond your current 1000 mg daily. 2, 3, 4
• Instead, add an SGLT2 inhibitor and/or GLP-1 RA to achieve better glucose control and kidney protection. 1, 2

Furosemide and Diuretic Management

Continue furosemide 40 mg daily at eGFR 44 mL/min/1.73 m² but monitor electrolytes and volume status every 3–6 months. 1, 2

Furosemide Dosing at Your eGFR

• Furosemide can be safely used at eGFR 44 mL/min/1.73 m² without dose adjustment, though loop diuretics become less effective as kidney function declines. 1
• If volume overload worsens, you may need higher doses of furosemide (not lower) because loop diuretics require higher doses to achieve the same effect at lower eGFR. 1

Monitoring for Complications

• Monitor for volume depletion, which increases risk of metformin accumulation and acute kidney injury. 1, 2
• Check electrolytes (sodium, potassium, bicarbonate) every 3–6 months to detect hypokalemia, hyponatremia, or metabolic alkalosis. 1
• Assess for metabolic acidosis, which becomes more common at eGFR <60 mL/min/1.73 m². 1

Interaction with Losartan/HCTZ

• Your combination of losartan 100 mg + hydrochlorothiazide 25 mg + furosemide 40 mg requires careful monitoring for hypotension, hyperkalemia (from losartan), and hypokalemia (from diuretics). 1
• At eGFR 44 mL/min/1.73 m², continue the ACE inhibitor/ARB (losartan) for kidney protection unless hyperkalemia develops. 1
• The hydrochlorothiazide component becomes less effective at eGFR <30 mL/min/1.73 m² but is still reasonable at your current eGFR. 1

Common Pitfalls to Avoid

• Do not discontinue metformin prematurely at eGFR 44 mL/min/1.73 m²—this level is well above the threshold (eGFR <30) requiring discontinuation. 2, 3
• Do not use serum creatinine alone to guide metformin decisions; always use eGFR, as creatinine-based cutoffs are outdated and lead to inappropriate discontinuation, especially in elderly or small-statured patients. 2, 3
• Do not delay adding an SGLT2 inhibitor while waiting for A1c to worsen—the kidney and cardiovascular benefits occur independent of glucose control and are time-sensitive. 1
• Do not stop SGLT2 inhibitors due to the initial 3–5 mL/min/1.73 m² eGFR dip—this is expected and protective. 1
• Do not forget to hold metformin during acute illness, contrast procedures, or if eGFR drops below 30 mL/min/1.73 m². 2, 3

Summary Algorithm for Your Specific Case

1. Continue metformin 500 mg twice daily (1000 mg total) without dose reduction. 2, 3, 4
2. Add canagliflozin or dapagliflozin immediately for kidney and cardiovascular protection. 1, 2
3. Consider adding a GLP-1 RA (dulaglutide, liraglutide, or semaglutide) if A1c remains >7.5% after 3 months on SGLT2 inhibitor. 1
4. Continue furosemide 40 mg daily with electrolyte monitoring. 1
5. Monitor eGFR and electrolytes every 3–6 months. 1, 2, 4
6. Reduce metformin to 500 mg daily (or discontinue) if eGFR falls below 30 mL/min/1.73 m². 2, 3, 4
7. Hold metformin temporarily during acute illness or contrast procedures. 2, 3