I have been taking Hyzar (losartan) for 13 years and my eGFR fell from about 90 mL/min/1.73 m² last September to roughly 70 mL/min/1.73 m² now; should I continue the medication?

Continue Hyzaar (Losartan/HCTZ) with Close Monitoring

You should continue taking Hyzaar despite the eGFR decline from 90 to 70 mL/min/1.73 m², as this medication provides critical long-term kidney and cardiovascular protection that outweighs the observed decline. The drop in eGFR you're experiencing is concerning and warrants investigation, but it is not an automatic indication to stop your ARB therapy.

Why Continue the Medication

Expected vs. Problematic eGFR Changes

The most recent KDIGO 2024 guidelines explicitly state that you should continue ACE inhibitors or ARBs even when eGFR falls below 30 mL/min/1.73 m² 1. Your current eGFR of 70 places you well above this threshold. The guidelines emphasize that ARBs like losartan should be continued unless specific complications arise 1.

A critical distinction: ARBs typically cause an acute eGFR dip of up to 30% within the first 2-4 weeks of initiation or dose increase 2, 3. However, you've been on this medication for 13 years, so this recent decline over several months represents something different—either disease progression or another contributing factor, not the expected hemodynamic effect of the drug.

Long-Term Kidney Protection

Research demonstrates that patients who experience an initial eGFR decline with losartan actually have slower long-term kidney function decline 4. This paradoxical finding shows that the acute hemodynamic changes predict better long-term outcomes. After 13 years of stable therapy, your kidneys have adapted to the medication's effects.

What Needs Immediate Attention

Investigate the Cause of Decline

Your 20-point eGFR drop over approximately 6 months (from 90 to 70) requires evaluation for:

• Volume depletion: The hydrochlorothiazide component can cause excessive fluid loss, especially with illness, heat exposure, or inadequate fluid intake 5
• Medication interactions: NSAIDs (ibuprofen, naproxen) combined with ARBs significantly worsen kidney function 5
• Acute kidney injury: Intercurrent illness, dehydration, or other nephrotoxic exposures
• Disease progression: Worsening of underlying kidney disease unrelated to the medication
• Bilateral renal artery stenosis: Though rare, ARBs can unmask this condition 5

Required Monitoring

According to current guidelines, you need 1, 3:

• Check within 2-4 weeks: Serum creatinine, potassium, and blood pressure
• If creatinine rises >30% from your new baseline: Consider reducing dose or investigating alternative causes, but don't automatically discontinue 3
• If creatinine rises persistently >30%: This warrants nephrology referral 1
• Monitor potassium: Hyperkalemia is manageable with dietary changes or potassium binders rather than stopping the ARB 1

When to Actually Stop or Reduce Hyzaar

The 2024 KDIGO guidelines specify you should reduce or discontinue only if 1:

1. Symptomatic hypotension that doesn't resolve with volume management
2. Uncontrolled hyperkalemia (>6 mEq/L) despite medical management including potassium binders
3. Serum creatinine rises >30% within 4 weeks of a dose change and remains elevated
4. eGFR falls to <15 mL/min/1.73 m² to reduce uremic symptoms while preparing for dialysis

Your eGFR of 70 doesn't meet any of these criteria.

Practical Management Algorithm

Immediate steps:

1. Verify the eGFR measurement: Repeat basic metabolic panel within 1-2 weeks to confirm the decline
2. Review recent medications: Stop any NSAIDs immediately if you're taking them 5
3. Assess volume status: Ensure adequate hydration; consider temporarily reducing HCTZ dose if volume depleted 5
4. Check for intercurrent illness: Recent infections, contrast dye exposure, or other acute events

If eGFR remains 60-70 after repeat testing:

• Continue Hyzaar at current dose
• Increase monitoring frequency to every 3-6 months 6
• Consider adding an SGLT2 inhibitor (like empagliflozin or dapagliflozin) for additional kidney protection if you have diabetes or albuminuria 7, 1

If eGFR continues declining or falls below 60:

• Maintain losartan component (the ARB provides ongoing protection) 1
• Consider switching from HCTZ to a loop diuretic if you need continued diuretic therapy, as thiazides become less effective below eGFR 30 5
• Refer to nephrology for comprehensive evaluation

Critical Pitfalls to Avoid

Don't stop the ARB prematurely. The FDA label for Hyzaar notes that changes in renal function "were reversible upon discontinuation of therapy" 5, but this refers to acute changes, not your situation after 13 years. Stopping losartan after long-term use removes critical kidney protection and may accelerate decline.

Don't assume the medication caused this decline. After 13 years of stable use, the medication itself is unlikely to be the primary culprit. The decline more likely represents natural disease progression or a new contributing factor.

Don't ignore the hydrochlorothiazide component. At eGFR 70, HCTZ remains effective, but it can contribute to volume depletion and prerenal azotemia 5. Your doctor may need to adjust this component while maintaining the losartan.

The evidence strongly supports continuing ARB therapy through declining kidney function, with the most recent 2025 KDIGO commentary reaffirming that these medications should be continued even to very low eGFR levels 7. Your focus should be on identifying and addressing the cause of decline while maintaining the proven kidney-protective benefits of your current regimen.