Can drinking more fluids improve estimated Glomerular Filtration Rate (eGFR)?

Can Drinking More Fluids Improve eGFR?

Drinking more fluids does not improve eGFR and may actually worsen kidney outcomes in patients with chronic kidney disease, with both low and high plain water intake showing increased risk of kidney failure compared to moderate intake of 1.0-1.5 L/day. 1

Evidence Against Increased Fluid Intake for eGFR Improvement

Key Research Findings

The most recent and highest quality study directly addressing this question found a U-shaped relationship between plain water intake and kidney outcomes in CKD patients 1:

• Patients drinking <0.5 L/day had an 88% increased risk of kidney failure (HR 1.88,95% CI 1.02-3.47) compared to those drinking 1.0-1.5 L/day 1
• Patients drinking >2.0 L/day had a 55% increased risk of kidney failure (HR 1.55,95% CI 1.03-2.32) compared to the moderate intake group 1
• High plain water intake was significantly associated with faster eGFR decline 1
• Neither total water intake nor urine volume was associated with improved kidney outcomes 1

This study included 1,265 CKD patients with mean eGFR of 32 mL/min/1.73 m² followed from 2013-2019, making it the most relevant evidence for clinical practice 1.

Guideline Recommendations on Hydration

Current guidelines recommend avoiding both volume depletion and overhydration when measuring kidney function 2:

• Patients should drink water to thirst in a pattern consistent with their usual fluid consumption 2
• Evidence supporting specific hydration protocols is limited, with data lacking in CKD patients 2
• Small studies show that high water intake (4 mL/kg every 30 minutes) resulted in lower measured GFR compared to low water intake (0.5 mL/kg every 30 minutes) in healthy individuals 2

Physiological Mechanisms Explaining Lack of Benefit

Fluid Overload and Kidney Function

Excessive fluid intake does not address the underlying pathophysiology of kidney disease 2:

• In heart failure and kidney disease, fluid overload results from neurohormonal-driven sodium avidity, not simple dehydration 2
• The body's compensatory mechanisms (RAAS activation) respond to volume changes, potentially worsening kidney function 2
• Low eGFR does not directly correlate with urine sodium handling—patients with low eGFR can still have high urine sodium 2

Potential Harms of Excessive Hydration

Increased water intake may suppress eGFR reduction mechanisms 3:

• Water supplementation (increasing intake from 1.3 L/day to 2.0 L/day) suppressed estimated glomerular filtration rate reduction in healthy Japanese adults 3
• While this study showed some benefits (decreased blood pressure, increased body temperature), the suppression of eGFR reduction suggests altered kidney hemodynamics 3

Clinical Implications and Recommendations

Optimal Fluid Intake Strategy

Maintain moderate plain water intake of 1.0-1.5 L/day in CKD patients 1:

• Avoid aggressive hydration protocols aimed at "improving" eGFR 1
• Counsel patients on sodium restriction to no more than 5 g of sodium chloride (2.0 g or 85 mmol of sodium) daily 2
• Monitor for signs of both dehydration and fluid overload 2

Important Caveats

Specific clinical scenarios require different approaches 2:

• In contrast-induced nephropathy prevention, hydration with isotonic saline is recommended (fluid replacement rate 1000 mL/h) 2
• In nephrogenic diabetes insipidus, salt-containing solutions should be avoided; use 5% dextrose instead 2
• Avoid prolonged fasting during kidney function testing, as this could lead to volume contraction 2

When to Adjust Fluid Management

Consider reducing diuretic doses rather than increasing fluid intake 4:

• Before starting SGLT2 inhibitors in patients with reduced eGFR, correct volume depletion first and consider reducing loop or thiazide diuretic doses 4
• In heart failure, matched fluid replacement with furosemide may be considered in very high-risk patients 2

Common Pitfalls to Avoid

• Do not advise CKD patients to "drink more water" to improve kidney function—this lacks evidence and may cause harm 1
• Do not confuse acute hydration for procedures (contrast studies, GFR measurement) with chronic fluid intake recommendations 2
• Do not use high dialysate sodium concentration or sodium profiling in dialysis patients, as this worsens volume status 2
• Recognize that eGFR fluctuates continually and may not accurately reflect true kidney function at all levels 5, 6