Interpreting a Creatinine Level of 1.37 mg/dL

Clinical Significance

• A creatinine level of 1.37 mg/dL falls within Grade 1 renal dysfunction according to clinical guidelines, with a creatinine level 1.5-2.0× above baseline, as defined by the American Society of Clinical Oncology 1
• This level may represent early chronic kidney disease (CKD), as it approaches the threshold of 1.5 mg/dL in men or 1.3 mg/dL in women that corresponds to an estimated GFR <60 mL/min/1.73m², according to the American Heart Association and the National Kidney Foundation 2, 3

Evaluation Approach

• Assess for potential alternative causes of elevated creatinine, including medications, volume status, recent contrast exposure, urinary tract infection or obstruction, and underlying comorbidities, as recommended by the American College of Cardiology 1
• Calculate estimated GFR using prediction equations, such as the MDRD or Cockcroft-Gault equation, rather than relying on serum creatinine alone, as suggested by the American College of Physicians 3
• Consider checking for albuminuria/proteinuria, as it provides additional prognostic information, according to the American Heart Association 2

Management Recommendations

• For patients without risk factors and normal baseline renal function, monitor creatinine regularly and avoid nephrotoxic medications when possible, as recommended by the American Society of Clinical Oncology 1, 4
• For patients with hypertension, ensure adequate blood pressure control, with a target <140/90 mmHg, and consider stricter BP control (<130/80 mmHg) for those with proteinuria or diabetes, as recommended by the American Heart Association 2
• For patients with heart failure, monitor renal function closely and adjust diuretic dosing if needed to prevent worsening renal function, as suggested by the American Heart Association 5

Special Considerations

• In patients with cirrhosis, a creatinine of 1.37 mg/dL may suggest developing hepatorenal syndrome, especially if accompanied by other clinical signs, as noted by the European Association for the Study of the Liver 6
• In patients receiving immune checkpoint inhibitors, this level may warrant closer monitoring for immune-related nephritis, as recommended by the American Society of Clinical Oncology 1, 7
• In elderly patients, serum creatinine may underestimate the degree of renal dysfunction due to decreased muscle mass, as noted by the American Geriatrics Society 3

Follow-up Recommendations

• Repeat creatinine measurement within 1-2 weeks to establish trend, as recommended by the American Society of Clinical Oncology and the National Kidney Foundation 1, 4
• If creatinine continues to rise or exceeds 2.0 mg/dL, consider nephrology consultation, as suggested by the American Society of Nephrology and the National Kidney Foundation 1, 3

Assessment and Management of a Serum Creatinine of 1.37 mg/dL

Clinical Significance

• A serum creatinine of 1.37 mg/dL is near the threshold that defines renal insufficiency (≥1.5 mg/dL in men or ≥1.3 mg/dL in women, corresponding to an estimated GFR < 60 mL/min/1.73 m²), therefore it warrants immediate calculation of eGFR to determine whether early chronic kidney disease is present. 8
• Serum creatinine alone is insufficient for assessing kidney function because it is influenced by muscle mass, age, sex, race, and dietary factors, which can mask the true glomerular filtration rate. The National Kidney Foundation highlights this limitation. 9

Immediate Evaluation

• eGFR should be calculated promptly using the MDRD or Cockcroft‑Gault equations, as these formulas adjust for age, sex, race, and body size, providing a more accurate estimate of kidney function than creatinine alone. 9
• To differentiate acute kidney injury (AKI) from chronic kidney disease, assess whether the creatinine has risen ≥ 0.3 mg/dL within 48 hours or ≥ 50 % from baseline; such changes meet the AKI definition. 10
• Screening for albuminuria or proteinuria is essential because the presence and magnitude of urinary protein add prognostic information and aid in CKD staging. 8

Population‑Specific Implications

• In women, a creatinine of 1.37 mg/dL exceeds the gender‑specific threshold (≥1.3 mg/dL) and therefore indicates CKD Stage 3 or higher (eGFR < 60 mL/min/1.73 m²). 8

Medication Management

• Dosing of renally cleared medications should be adjusted based on the calculated eGFR rather than the raw creatinine value to avoid under‑ or overdosing. 11

Common Pitfalls to Avoid

• Do not consider a creatinine of 1.37 mg/dL “normal” without first calculating eGFR, especially in elderly patients, women, or individuals with low muscle mass, because creatinine may substantially underestimate renal dysfunction in these groups. 9
• Avoid using 24‑hour urine collections for creatinine clearance; eGFR equations are more reliable and less prone to collection errors. 9