Creatinine, Blood

Creatinine, Blood

Synonym/acronym: N/A.

Common use

To assess kidney function found in acute and chronic renal failure, related to drug reaction and disease such as diabetes.


Serum (1 mL) collected in a red- or red/gray-top tube. Plasma (1 mL) collected in a green-top (heparin) tube is also acceptable.

Normal findings

(Method: Spectrophotometry)
AgeConventional UnitsSI Units (Conventional Units × 88.4)
Newborn0.31–1.21 mg/dL27–107 micromol/L
Infant0.31–0.71 mg/dL27–63 micromol/L
1–5 yr0.31–0.51 mg/dL27–45 micromol/L
6–10 yr0.51–0.81 mg/dL45–72 micromol/L
Adult male0.61–1.21 mg/dL54–107 micromol/L
Adult female0.51–1.11 mg/dL45–98 micromol/L

Values in older adults remain relatively stable after a period of decline related to loss of muscle mass during the transition from adult to older adult.

The National Kidney Foundation recommends the use of two decimal places in reporting serum creatinine for use in calculating estimated glomerular filtration rate.


Creatine resides almost exclusively in skeletal muscle, where it participates in energy-requiring metabolic reactions. A small amount of creatine is irreversibly converted to creatinine by the liver, which then circulates to the kidneys and is excreted. The amount of creatinine generated in an individual is proportional to the mass of skeletal muscle present and remains fairly constant throughout the lifespan; its consistency in production and clearance is the reason that creatinine is used as an indicator of renal function. Creatinine values normally decrease with age owing to diminishing muscle mass. Conditions involving degenerative muscle wasting or massive muscle trauma from a crushing injury will also result in decreased creatinine levels. Blood urea nitrogen (BUN) is often ordered with creatinine for comparison. The BUN/creatinine ratio is also a useful indicator of kidney disease. The ratio should be between 10:1 and 20:1. The creatinine clearance test measures a blood sample and a urine sample to determine the rate at which the kidneys are clearing creatinine from the blood; this reflects the glomerular filtration rate, or GFR (see monograph titled “Creatinine, Urine, and Creatinine Clearance, Urine”).

Chronic kidney disease (CKD) is a significant health concern worldwide. An international effort to standardize methods to identify and monitor CKD has been undertaken by the National Kidney Disease Education Program (NKDEP), the International Confederation of Clinical Chemistry and Laboratory Medicine, and the European Communities Confederation of Clinical Chemistry. International efforts have resulted in development of an isotope dilution mass spectrometry (IDMS) reference method for standardized measurement of creatinine. The National Kidney Foundation (NKF) has recommended use of an equation to estimate glomerular filtration rate (eGFR). The equation is based on factors identified in the NKF Modification of Diet in Renal Disease (MDRD) study. The equation includes four factors: serum or plasma creatinine value, age (in years), gender, and race. The equation is valid only for patients between the ages of 18 and 70. A correction factor is incorporated in the equation if the patient is African American because CKD is more prevalent in African Americans; results are approximately 20% higher. It is very important to know whether the creatinine has been measured using an IDMS traceable test method because the values will differ; results are lower. The equations have not been validated for pregnant women (GFR is significantly increased in pregnancy); patients younger than 18 or older than 70; patients with serious comorbidities; or patients with extremes in body size, muscle mass, or nutritional status. eGFR calculators can be found at the National Kidney Disease Education Program (

Cystatin C, also known as cystatin 3 and CST3, is now recognized as a useful marker for kidney damage and monitor of function in transplanted kidneys. It is a low molecular weight molecule belonging in the family of proteinase inhibitors. Cystatin C is produced by all nucleated cells in the body and is freely filtered by the glomerular membrane in the kidney. It is not secreted by the kidney tubules and although a small amount is reabsorbed by the kidney tubules, it is metabolized in the tubules and does not re-enter circulation. Therefore, its serum concentration is directly proportional to kidney function. It is believed to be a better marker of kidney function than creatinine because levels are independent of weight and height, diet, muscle mass, age, and sex. Normal values for individuals age 1–50 years are 0.56–0.9 mg/L and 0.58–1.08 mg/L for age 50 years and older.

This procedure is contraindicated for



  • Assess a known or suspected disorder involving muscles in the absence of renal disease
  • Evaluate known or suspected impairment of renal function

Potential diagnosis

Increased in

  • Acromegaly (related to increased muscle mass)
  • Congestive heart failure (related to decreased renal blood flow)
  • Dehydration (related to hemoconcentration)
  • Gigantism (related to increased muscle mass)
  • Poliomyelitis (related to increased release from damaged muscle)
  • Pregnancy induced hypertension (related to reduced GFR and decreased urinary excretion)
  • Renal calculi (related to decreased renal excretion due to obstruction)
  • Renal disease, acute and chronic renal failure (related to decreased urinary excretion)
  • Rhabdomyolysis (related to increased release from damaged muscle)
  • Shock (related to increased release from damaged muscle)

Decreased in

    Decreased muscle mass (related to debilitating disease or increasing age) Hyperthyroidism (related to increased GFR) Inadequate protein intake (related to decreased muscle mass) Liver disease (severe) (related to fluid retention) Muscular dystrophy (related to decreased muscle mass) Pregnancy (related to increased GFR and renal clearance) Small stature (related to decreased muscle mass)

Critical findings

  • Adults
  • Potential critical value is greater than 7.4 mg/dL (SI: 654.2 micromol/L) (nondialysis patient).

  • Children
  • Potential critical value is greater than 3.8 mg/dL (SI: 336 micromol/L) (nondialysis patient).

  • Note and immediately report to the health-care provider (HCP) any critically increased values and related symptoms.

  • It is essential that a critical finding be communicated immediately to the requesting health-care provider (HCP). A listing of these findings varies among facilities.

  • Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. Notification processes will vary among facilities. Upon receipt of the critical value the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, Hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical value, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.

  • Chronic renal insufficiency is identified by creatinine levels between 1.5 and 3 mg/dL; chronic renal failure is present at levels greater than 3 mg/dL.

  • Possible interventions may include renal or peritoneal dialysis and organ transplant, but early discovery of the cause of elevated creatinine levels might avoid such drastic interventions.

Interfering factors

  • Drugs and substances that may increase creatinine levels include acebutolol, acetaminophen (overdose), acetylsalicylic acid, aldatense, amikacin, amiodarone, amphotericin B, arginine, arsenicals, ascorbic acid, asparaginase, barbiturates, capreomycin, captopril, carbutamide, carvedilol, cephalothin, chlorthalidone, cimetidine, cisplatin, clofibrate, colistin, corn oil (Lipomul), cyclosporine, dextran, doxycycline, enalapril, ethylene glycol, gentamicin, indomethacin, ipodate, kanamycin, levodopa, mannitol, methicillin, methoxyflurane, mitomycin, neomycin, netilmicin, nitrofurantoin, NSAIDs, oxyphenbutazone, paromomycin, penicillin, pentamidine, phosphorus, plicamycin, radiographic agents, semustine, streptokinase, streptozocin, tetracycline, thiazides, tobramycin, triamterene, vancomycin, vasopressin, viomycin, and vitamin D.
  • Drugs that may decrease creatinine levels include citrates, dopamine, ibuprofen, and lisinopril.
  • High blood levels of bilirubin and glucose can cause false decreases in creatinine.
  • A diet high in meat can cause increased creatinine levels.
  • Ketosis can cause a significant increase in creatinine.
  • Hemolyzed specimens are unsuitable for analysis.

Nursing Implications and Procedure

Potential nursing problems

ProblemSigns & SymptomsInterventions
Fluid volume (Related to excess fluid and sodium intake; compromised renal function)Excess: edema, shortness of breath, increased weight, ascites, rales, rhonchi, and diluted laboratory values; distended neck veins; tachycardia; restlessness Record daily weight and monitor trends; ensure accurate intake and output; monitor laboratory values that reflect alterations in fluid status (potassium, blood urea nitrogen, creatinine, calcium, hemoglobin, and hematocrit, sodium); manage underlying cause of fluid alteration; monitor urine characteristics and respiratory status; establish baseline assessment data; assess and trend heart rate and blood pressure; assess for symptoms of fluid overload such as Jugular Venous Distension (JVD), shortness of breath, dyspnea, crackles; ensure low-sodium diet; administer prescribed diuretic; administer prescribed antihypertensive; elevate feet when sitting; monitor oxygenation with pulse oximetry; administer oxygen as appropriate; elevate the head of the bed; administer prescribed antihypertensives
Cardiac output (Related to excess fluid volume; pericarditis; electrolyte imbalance; toxin accumulation)Weak peripheral pulses; slow capillary refill; decreased urinary output; cool clammy skin; tachypnea; dyspnea; altered level of consciousness; abnormal heart sounds; fatigue; hypoxia; loud holosystolic murmur; EKG changes; increased JVDAssess peripheral pulses and capillary refill; monitor blood pressure and check for orthostatic changes; assess respiratory rate, breath sounds, and orthopnea; assess skin color and temperature; assess level of consciousness; monitor urinary output; use pulse oximetry to monitor oxygenation; monitor EKG; administer ordered inotropic and peripheral vasodilator medications, nitrates; provide oxygen administration; administer as prescribed (sodium bicarbonate, glucose, insulin drip, potassium excretion resin, calcium salt)
Protection (Anemia-related to bone marrow suppression secondary to renal insufficiency [erythropoietic]; red cell destruction secondary to altered plasma environment; nutritional deficiency; decreased and defective platelets; blood loss; ineffective clotting)Pallor; fatigue; weakness; shortness of breath; anxiety; easy bruising; increased clotting timeAssess for symptoms of anemia (fatigue, pallor, decreased activity); observe for prolonged bleeding associated with ineffective clotting; use pulse oximetry or arterial blood gases to assess oxygenation; administer oxygen as required; administer blood or blood products as required; administer prescribed epoetin alfa; use bleeding precautions (avoid aspirin products, avoid trauma, avoid constipation, avoid forceful nose blowing that could cause nosebleed)
Sexuality (Related to amenorrhea; decreased libido; lack of ovulation; testicular atrophy; impotence; psychological impairment secondary to physical effects of renal insufficiency)Reduced sexual function; decreased sexual satisfaction; alteration in the relationship with partnerAssess perception of reported change in sexual function; assess the emotional impact of decreased libido (depression, altered self-esteem, altered personal relationships); assess for need of counseling; encourage verbalization of feelings; discuss alternative forms of intimate expression; discuss medical treatments that may improve sexual function


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in assessing kidney function.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s genitourinary and musculoskeletal systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.
  • Instruct the patient to refrain from excessive exercise for 8 hr before the test.


  • Potential complications: N/A
  • Ensure that the patient has complied with activity restrictions; assure that activity has been restricted for at least 8 hr prior to the procedure.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Nutritional Considerations: Increased creatinine levels may be associated with kidney disease. The nutritional needs of patients with kidney disease vary widely and are in constant flux. Anorexia, nausea, and vomiting commonly occur, prompting the need for continuous monitoring for malnutrition, especially among patients receiving long-term hemodialysis therapy.
  • Recognize anxiety related to test results and be supportive of impaired activity related to fear of shortened life expectancy. Help the patient to cope with long-term implications. Recognize that anticipatory anxiety and grief related to potential lifestyle changes may be expressed when someone is faced with a chronic disorder.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
  • Patient Education

    • Discuss the implications of abnormal test results on the patient’s lifestyle.
    • Provide teaching and information regarding the clinical implications of the test results, as appropriate.
    • Educate the patient regarding access to counseling services.
    • Provide contact information, if desired, for the National Kidney Foundation ( or the National Kidney Disease Education Program (
  • Expected Patient Outcomes

    • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP.
    • Answer any questions or address any concerns voiced by the patient or family.
    • Instruct the patient to resume usual activity as directed by the HCP.
    • Knowledge
    • States causes of decreased libido
    • Identifies causes of anemia
    • Skills
    • Demonstrates proficiency in taking prescribed medication accurately
    • Demonstrates proficiency in selecting activities that decrease bleeding risk
    • Attitude
    • Discusses the efficacy of counseling to repair personal relationship secondary to intimacy concerns
    • States approach to care planning for sexual dysfunction is realistic

Related Monographs

  • Related tests include anion gap, antimicrobial drugs, ANF, BNP, biopsy muscle, blood gases, BUN, calcium, calculus kidney stone panel, CT abdomen, CT renal, CK and isoenzymes, creatinine clearance, cystoscopy, echocardiography, echocardiography transesophageal, electrolytes, EMG, ENG, glucagon, glucose, glycolated hemoglobin, insulin, IVP, KUB studies, lung perfusion scan, MRI venography, microalbumin, osmolality, phosphorus, renogram, retrograde ureteropyelography, TSH, thyroxine, US abdomen, uric acid, and UA.
  • Refer to the Genitourinary and Musculoskeletal systems tables at the end of the book for related tests by body system.
References in periodicals archive ?
Wearable sensors for measuring blood trends like glucose, cholesterols, triglycerides, potassium, serum creatinine, blood pressure etc in a periodic basis.
The serum electrolytes, BUN, creatinine, blood glucose, and liver function tests were within normal ranges.
It is worth noting, though, that even after adjustment for known predictors of in-hospital mortality in acute heart failure--including age, gender, blood urea nitrogen, creatinine, blood pressure, and dyspnea at rest--patients in the lowest BMI quartile had a highly significant 46% greater in-hospital mortality than did those in the top quartile, who had a BMI of at least 33.
Creatinine, Blood Urea Nitrogen: In controlled clinical trials minor increases in blood urea nitrogen and serum creatinine, reversible upon discontinuation of therapy, were observed in about 0.