Management of Patients with Normal Serum Creatinine
For patients with diabetes who have normal serum creatinine, normal blood pressure, and normal urinary albumin-to-creatinine ratio (<30 mg/g), ACE inhibitors or ARBs are NOT recommended for primary prevention of chronic kidney disease. 1
Critical Understanding: Normal Creatinine Does Not Equal Normal Kidney Function
Serum creatinine alone is an inadequate marker of renal function, particularly in elderly patients, women, and those with low muscle mass. 2, 3 Among older adults with stage 3 CKD, 80.6% had creatinine values ≤1.5 mg/dL, and 38.6% had values ≤1.2 mg/dL 3. This means you must calculate estimated glomerular filtration rate (eGFR) rather than relying on serum creatinine values alone.
Essential Screening Approach
For Patients with Diabetes or Hypertension:
- Measure both eGFR and urinary albumin-to-creatinine ratio (UACR) annually to properly assess kidney function 1
- Use the CKD-EPI equation to calculate eGFR, which should be automatically reported by laboratories 1
- Assess changes from baseline values, not just whether values fall within population normal ranges 1
Screening Frequency Based on Risk:
The frequency of monitoring should be tailored to individual risk factors 4:
- Age <50 years with diabetes/hypertension: Every 2-3 years is reasonable 4
- Age 50-70 years with diabetes/hypertension: Annual testing 4
- Age >70 years with diabetes/hypertension: Annual testing 4
- Presence of heart failure: More frequent monitoring (every 6 months) 4
Management Algorithm by Clinical Scenario
Scenario 1: Normal Creatinine, Normal eGFR (≥60), Normal UACR (<30 mg/g)
- Do NOT initiate ACE inhibitor or ARB for kidney protection if blood pressure is normal 1
- Continue annual screening of eGFR and UACR 1
- Optimize glycemic control and blood pressure if diabetes or hypertension present 1
Scenario 2: Normal Creatinine BUT eGFR 45-59 (Stage G3a CKD)
This represents occult kidney disease that creatinine missed 2, 3:
- For patients with type 2 diabetes: Initiate SGLT2 inhibitor with demonstrated benefit to reduce CKD progression and cardiovascular events 1
- If UACR 30-299 mg/g: Add ACE inhibitor or ARB 1
- Monitor serum creatinine and potassium 7-14 days after initiating ACE inhibitor/ARB, then at routine visits 1
- Increase monitoring frequency to 2-4 times per year 1
Scenario 3: Normal Creatinine BUT eGFR 30-44 (Stage G3b CKD)
- Refer to nephrology for evaluation 1
- For type 2 diabetes: Initiate SGLT2 inhibitor (if eGFR ≥20) 1
- Consider nonsteroidal MRA (finerenone) if eGFR ≥25 and albuminuria present 1
- Limit dietary protein to 0.8 g/kg/day 1
- Monitor 3-4 times per year 1
Critical Monitoring Principles
When Using Nephrotoxic Medications:
For patients on ACE inhibitors, ARBs, or diuretics:
- Check serum creatinine and potassium 7-14 days after initiation or dose change 1
- Do NOT discontinue renin-angiotensin system blockade for creatinine increases ≤30% above baseline in absence of volume depletion 1
- If creatinine rises >30%: Repeat within 2 weeks; if sustained, adjust dosage 1
For patients on ciclosporin:
- Monitor creatinine fortnightly for first 2 months, then monthly 1
- Assess changes relative to patient's baseline, not population norms 1
For patients on bisphosphonates (pamidronate/zoledronic acid):
- Check serum creatinine before each dose 1
- Screen for albuminuria every 3-6 months 1
- Reduce initial dose in patients with pre-existing renal impairment 1
Common Pitfalls to Avoid
Assuming normal creatinine equals normal kidney function in elderly patients, women, or those with low muscle mass 2, 3
Reacting to single creatinine measurements rather than sustained changes 1
Discontinuing ACE inhibitors/ARBs for minor creatinine increases (<30%) without evidence of volume depletion 1
Using ACE inhibitors/ARBs for primary prevention in patients with truly normal kidney function (normal eGFR, normal UACR, normal BP) 1
Failing to calculate eGFR and relying solely on serum creatinine values 1, 2, 3