A patient with an estimated glomerular filtration rate (eGFR) of 43 mL/min/1.73 m²—what chronic kidney disease (CKD) stage does this correspond to and what immediate evaluation and management steps are indicated?

Management of eGFR 43 mL/min/1.73 m²

An eGFR of 43 mL/min/1.73 m² indicates Stage G3b chronic kidney disease (moderately to severely decreased kidney function), and immediate nephrology referral is warranted because this falls below the 45 mL/min/1.73 m² threshold for specialist consultation. 1

CKD Stage Classification and Prognosis

• This eGFR value places the patient in Stage G3b CKD (eGFR 30-44 mL/min/1.73 m²), representing loss of approximately two-thirds of normal kidney function. 2
• Stage G3b carries substantially higher risks than Stage G3a (eGFR 45-59): increased cardiovascular disease risk, faster CKD progression, and elevated mortality compared to earlier stages. 2
• The diagnosis requires confirmation with a repeat eGFR measurement within 3 months, as CKD is defined by persistent abnormalities lasting ≥3 months. 2

Immediate Nephrology Referral

• Refer to nephrology immediately when eGFR < 45 mL/min/1.73 m²—this patient at 43 mL/min/1.73 m² meets this criterion. 1, 2
• Additional referral indications include: uncertainty about CKD etiology, difficult management issues, rapidly progressing kidney disease (eGFR decline ≥5 mL/min/1.73 m² per year), or confirmed proteinuria with UACR ≥300 mg/g. 2

Comprehensive Laboratory Evaluation

Screen immediately for CKD complications when eGFR <60 mL/min/1.73 m²: 2

• Electrolyte panel: serum potassium, calcium, phosphorus, bicarbonate (metabolic acidosis)
• Mineral-bone disorder markers: parathyroid hormone (PTH) every 6-12 months in Stage G3b 2
• Anemia screening: complete blood count, serum iron studies (ferritin, transferrin saturation) 2
• Proteinuria assessment: urine albumin-to-creatinine ratio (UACR) annually 2
• Monitoring frequency: measure eGFR and UACR at least annually; laboratory monitoring for complications every 6-12 months for Stage 3 CKD 2

Blood Pressure and Cardiovascular Management

• Target blood pressure <130/80 mmHg to slow CKD progression. 2
• Initiate ACE inhibitor or ARB as first-line therapy if albuminuria is present (UACR ≥30 mg/g), using maximally tolerated doses. 1, 2
• Continue ACE inhibitor/ARB even if serum creatinine rises ≤30% after initiation, unless volume depletion is evident—this modest rise predicts long-term renal protection. 2
• Monitor serum creatinine and potassium 1-2 weeks after initiating or titrating ACE inhibitor/ARB therapy. 2
• Aggressive cardiovascular risk factor modification is critical, as cardiovascular mortality often exceeds the risk of progressing to end-stage renal disease at this stage. 2

Medication Management and Safety

• Review and adjust dosing of all medications when eGFR <60 mL/min/1.73 m²—many drugs require dose reduction at this level. 2
• Strictly avoid NSAIDs, as they reduce renal blood flow and can precipitate acute kidney injury. 2
• Metformin is safe to continue at eGFR 43 mL/min/1.73 m² (≥30 mL/min/1.73 m²), but should be discontinued if eGFR falls below 30 mL/min/1.73 m². 1
• SGLT2 inhibitors are recommended for patients with type 2 diabetes and eGFR ≥30 mL/min/1.73 m² to reduce CKD and cardiovascular disease progression. 1
• GLP-1 receptor agonists are preferred additional agents for glycemic control when metformin and SGLT2 inhibitors are insufficient or not tolerated, particularly in patients with atherosclerotic cardiovascular disease. 1

Glycemic Control (if Diabetic)

• Target HbA1c of 7% to delay CKD progression—intensive glucose control delays onset and progression of albuminuria and reduces eGFR decline in both type 1 and type 2 diabetes. 2
• First-line therapy includes metformin and an SGLT2 inhibitor for patients with type 2 diabetes and eGFR ≥30 mL/min/1.73 m². 1

Dietary and Lifestyle Modifications

• Limit dietary protein to 0.8 g/kg body weight per day to reduce hyperfiltration injury and slow CKD progression. 2
• Restrict sodium to <2 g/day to reduce blood pressure and maximize diuretic effectiveness if needed. 2
• Moderate-intensity physical activity for ≥150 minutes per week is recommended, and patients should avoid sedentary behavior. 1
• Smoking cessation is essential for slowing CKD progression and reducing cardiovascular risk. 2

Vaccination

• Hepatitis B vaccination is indicated early in patients likely to progress to end-stage kidney disease. 2

Critical Pitfalls to Avoid

• Do not underestimate the severity of Stage G3b disease—despite being grouped under "stage 3," Stage G3b carries significantly higher risks than Stage G3a and warrants more aggressive monitoring and nephrology involvement. 2
• Do not rely on serum creatinine alone—always calculate and use eGFR for assessment of kidney function. 2
• If creatinine-based eGFR appears discordant with the clinical picture, measure cystatin C-based eGFR, as creatinine estimates are inaccurate in approximately 16-20% of individuals with eGFR <60 mL/min/1.73 m². 2
• Do not discontinue ACE inhibitor/ARB prematurely for modest creatinine increases (<30%)—stopping removes important renoprotective and cardiovascular benefits. 2
• Cardiovascular risk is markedly elevated at this stage of CKD and often exceeds the risk of progressing to dialysis, requiring aggressive risk factor modification. 2