Is a serum creatinine (Cr) level of 0.85 mg/dL abnormal?

Interpreting a Serum Creatinine Level of 0.85 mg/dL

A serum creatinine level of 0.85 mg/dL is within the normal reference range and is not considered abnormal for most adults.

Normal Reference Ranges for Serum Creatinine

• Serum creatinine values vary by sex, age, and ethnicity, with normal reference ranges typically being:

  • For men: 0.53-1.11 mg/dL 1
  • For non-menopausal women: 0.42-0.77 mg/dL 2
  • For menopausal women: 0.42-0.88 mg/dL 2

• Mean serum creatinine levels in the US population are:

  • Women: 0.96 mg/dL 1
  • Men: 1.16 mg/dL 1

Factors Affecting Serum Creatinine Interpretation

• Serum creatinine levels are influenced by multiple factors beyond just kidney function:

  • Age (levels increase with age) 1
  • Gender (higher in men than women) 1, 2
  • Ethnicity (highest in non-Hispanic blacks, lower in non-Hispanic whites, lowest in Mexican-Americans) 1
  • Muscle mass (primary source of creatinine production) 3
  • Protein intake and diet 3

• A single creatinine measurement should not be used in isolation to assess kidney function, as it may not accurately reflect glomerular filtration rate (GFR) 4

Clinical Significance of Creatinine Level 0.85 mg/dL

• A value of 0.85 mg/dL falls within normal reference ranges for both adult men and women 1, 2

• For acute kidney injury (AKI) diagnosis, what matters is not the absolute value but rather:

  • An increase of ≥0.3 mg/dL within 48 hours, or
  • An increase to ≥1.5 times baseline within 7 days 5

• For chronic kidney disease (CKD), abnormality of kidney function must be present for >3 months 5

Limitations of Serum Creatinine as a Screening Test

• Serum creatinine is an inadequate screening test for renal function, particularly in elderly patients 6

• Normal serum creatinine values can mask significant renal impairment, especially in:

  • Elderly patients 6
  • Patients with low muscle mass 3
  • Women (who typically have lower muscle mass than men) 1

• A serum creatinine of 0.85 mg/dL may still be associated with reduced GFR in certain populations, requiring calculation of estimated GFR using formulas such as:

  • Cockcroft-Gault formula 5
  • MDRD (Modification of Diet in Renal Disease) formula 5

Clinical Approach to Interpreting Creatinine Values

• For more accurate assessment of kidney function, calculate estimated GFR using validated formulas that account for age, sex, race, and body size 5

• Monitor trends in serum creatinine rather than relying on a single value 5

• Small changes in serum creatinine (even 0.1 mg/dL) can be clinically significant when they represent a change from baseline 5

• In patients with suspected kidney disease, additional assessments should include urinalysis, urine albumin-to-creatinine ratio, and other relevant laboratory tests 5