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Lab Test: Creatinine (Serum) Level

    Lab Test
    • Creatinine (Serum)
    Description
    • Measurement of creatinine in serum or plasma to assess renal function
    Reference Range
    • Adults:  < 1.5 mg/dL (< 133 mcmol/L)
    • Adult women (18-60 years):  0.6-1.1 mg/dL (53-97 mcmol/L)
    • Adult men (18-60 years):  0.9-1.3 mg/dL (80-115 mcmol/L)
    • Men aged 60 to 90 years:  0.8-1.3 mg/dL (71-115 mcmol/L)
    • Women aged 60 to 90 years:  0.6-1.2 mg/dL (53-106 mcmol/L)
    • Men aged > 90 years:  1-.17 mg/dL (88-150 mcmol/L)
    • Women aged > 90 years:  0.6-1.3 mg/dL (53-115 mcmol/L)

    • Neonates:
      • Cord blood:  0.6-1.2 mg/dL (53-106 mcmol/L)
    • Newborn aged 1-4 days: 0.3-1 mg/dL (27-88 mcmol/L)
    • Infants: 0.2-0.4 mg/dL (18-35 mcmol/L)
    • Children:  0.3-0.7 mg/dL (27-62 mcmol/L)
    • Adolescents:  0.5-1 mg/dL (44-88 mcmol/L)* (PDR)
    • Less than 2 years:  0.1-0.4 mg/dL
    • 2 years to < 6 years:  0.2-0.5 mg/dL
    • 6 years to < 10 years: 0.3-0.6 mg/dL
    • 10 years to < 18 years:  0.4-1.0 mg/dL
    • 18 years to < 41 years: Female: 0.5-1.0 mg/dL
    • 18 years to < 41 years:  Male:  0.6-1.2 mg/dL
    • 41 years to < 61 years:  Female:  0.5-1.1 mg/dL
    • 41 years to < 61 years:  Male:  0.6-1.3 mg/dL
    • 61 years and above:  Female:  0.5-1.2 mg/dL
    • 61 years and above:  Male:  0.7-1.3 mg/dL
    • Critical Values:  > 4 mg/dL (indicates serious impairment in renal function)
    Indications & Uses
    • Acute adrenal insufficiency - level is usually elevated in acute adrenal insufficiency. 
    • Acute coronary syndrome - an elevated serum creatinine on presentation with acute myocardial infarction is associated with a markedly increased 1-year mortality, especially if associated with congestive heart failure
    • Cardiovascular system disease - in study of persons older than 65 years, 11.2% had an elevated baseline serum creatinine (SCr) level (greater than or equal to 1.5 mg/dL in men and 1.3 mg/dL in women).  Persons with an elevated SCr level had a higher:
      • Overall mortality: 76.7 vs 29.5/1,000 years
      • Cardiovascular mortality:  35.8 vs 13/1,000 years
      • CV disease risk:  54 vs 31.8/1,000 years
      • Stroke risk: 21.1 vs 11.9/1,000 years
      • Congestive heart failure risk:  38.7 vs 17/1,000 years
      • Symptomatic peripheral vascular disease risk:  10.6 vs 3.5/1,000 years
    • Heart failure - most patients with severe heart failure will have an increased blood urea nitrogen (BUN)-to-creatinine ratio greater than 20:1 (normal is 10:1)
    • Hemorrhagic shock - blood urea nitrogen and creatinine levels rise over the first few post-shock days typically in a fixed ratio of approximately 10:1
    • Hypothyroidism - level may be elevated and return to normal with thyroid hormone replacement
    • Initial evaluation and monitoring of diabetic ketoacidosis  - may be increased due to renal failure
    • Initial evaluation and monitoring of hyperosmolar hyperglycemic state - blood urea nitrogen to creatinine ratio may be greater than 30:1 on presentation due to dehydration
    • Metabolic acidosis - patients with metabolic acidosis secondary to chronic renal failure have elevated levels.  Anion gap metabolic acidosis develops when the glomerular filtration rate is less than 20 mL/minute (serum creatinine 4 to 5 mg/dL)
    • Submersion - serial measurements of serum creatinine are recommended in all submersion victims to monitor for the development of acute renal impairment
    • Suspected acute renal failure - measurement is particularly useful in renal failure because it is minimally affected by protein intake, hydration, and protein metabolism. 
    • Suspected and known ovarian hyperstimulation syndrome - creatinine level greater than 1.2 mg/dL indicates possible grade 5 OHSS and is an indication for hospital admission.  
    • Suspected and known preeclampsia - level greater than 1.2 mg/dl increases the certainty of a preeclampsia diagnosis, especially when it is associated with oliguria
    • Suspected chronic renal failure - SCr alone should not be used to assess kidney function.  Minor elevations of SCr may be consistent with substantial reduction in GFR.  Because of the wide range of SCr in normal persons, GFR must decline to approximately half the normal level before the SCr rises above the upper limit of normal. 
    • Suspected disseminated intravascular coagulation - increased SCr levels suggest end-stage organ damage or renal failure in patients with DIC. 
    • Suspected ehrlichiosis - SCr level greater than 1.2 mg/dl may be indicative of decreased renal function
    • Suspected post-streptococcal glomerulonephritis - the creatinine level is a more reliable indicator of renal function than BUN content, ad can be abnormal in more than 50% of patients with PSGN
    • Suspected renal manifestations of diabetes mellitus - SCr levels may not be elevated until more than 50% of kidney function is lost (i.e., a greater than 50% reduction in GFR)
    • Suspected rhabdomyolysis - in myoglobinuria with renal failure, the serum creatinine rises greater than 2.5 mg/dL in 24 hours due to the increased creatinine load, whereas in renal failure without myoglobinuria, levels rise an average of 2 mg/dL in 24 hours. 
    • Suspected sepsis - creatinine increase greater than 0.5 mg/dL may be associated with renal dysfunction in severe sepsis. 
    • Thromboembolic stroke - an elevated serum creatinine, in a patient presenting with stroke, may predict mortality.
    Clinical Application
    • Creatinine is a catabolic product of creatine phosphate, which is used in skeletal muscle contractions.  The daily production of creatine, and subsequently creatinine, depends on muscle mass, which fluctuates very little.  Creatinine, as blood urea nitrogen (BUN), is excreted entirely by the kidneys and therefore is directly proportional to renal excretory function.  With normal renal excretory function, the serum creatinine level should remain constant and normal. 
    • The creatinine level is affected minimally by hepatic function. 
    • The creatinine is used as an approximation of the glomerular filtration rate (GFR). In general, a doubling of creatinine suggests a 50% reduction in the GFR.  The BUN/creatinine ratio is a good measurement of kidney and liver function.  The normal range is 6 to 25, with 15.5 being the optimal adult value for this ratio. 
    • Increased levels may indicate:
      • Diseases affecting renal function, such as glomerulonephritis, pyelonephritis, acute tubular necrosis, urinary tract obstruction, reduced renal blood flow (e.g., shock, dehydration, congestive heart failure, atherosclerosis), diabetic nephropathy, nephritis, rhabdomyolysis, acromegaly, gigantism. 
    • Decreased levels may indicate:
      • Debilitation, decreased muscle mass (e.g., muscular dystrophy, myasthenia gravis)
    Related Tests
    • Creatinine clearance:  see medical calculators
    Drug-Lab Interactions
    • Results increased and/or show transient elevations in meat meals.
    • Results decreased in decreased muscle mass (elderly, debilitation) and pregnancy. 
    • Drugs that may increase creatinine values include: 
      • ACE inhibitors, aminoglycosides (e.g., gentamicin), cimetidine, fenofibrate, heavy-metal chemotherapeutic agents (e.g., cisplatin), and other nephrotoxic drugs such as cephalosporins (e.g., cefoxitin).
    Test Tube Needed
    • Marble top tube
    • Red top tube
    Procedure
    • Collect a venous blood sample. 
    • For pediatric patients, blood is usually drawn from a heel stick.
    • Apply pressure or a pressure dressing to the venipuncture site and observe the site for bleeding.
    Storage and Handling
    • Sample is stable at 4°C for 24 hours; should be frozen for longer periods.
    What To Tell Patient Before & After
    • Explain the procedure to the patient. 
    • Tell the patient that no fasting is required.
    References
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.
    • Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed.  St. Louis, Missouri. 2014.

MESH Terms & Keywords

  • Creatinine