- Red or tiger top tube
- 3-5 mL of venous blood
- Reject in case of hemolysis
- A test done as part of the basic or comprehensive metabolic panel (BMP or CMP)
- Creatinine is the breakdown product of muscle creatine phosphate
- The amount of creatinine generated in an individual is proportional to the mass of skeletal muscle present and remains fairly constant normally
- Creatinine is excreted in urine, by the kidneys
- An approximation of the glomerular filtration rate (GFR) can be calculated based upon age, gender, body weight and serum creatinine
- Creatinine levels are useful in assessing:
- Known or suspected impairment of renal function
- Known or suspected disorders involving muscles, in the absence of renal disease
- Creatinine levels increase when glomerular filtration is decreased
- Analysis of creatinine levels provides a more sensitive measure of renal damage than blood urea nitrogen (BUN) levels, however BUN and BUN/creatinine ratio may also be done to provide additional information
- BUN/Creatinine ratio is used to differentiate pre-renal, renal, and post-renal (obstructive) azotemia
- Creatinine level does not correlate well with minor or early kidney damage or disease. It may take significant (e.g. 50% of more nephrons affected) damage to result in a significant rise in creatinine.
- Creatinine has diurnal variation with higher values in the evening and night
- Day-to-day variation is 15-20%
- Serum creatinine values vary with:
- Age
- Body weight
- Gender
- Muscle mass
- Higher values are seen in men than in women
- Higher values are seen in Blacks than in Whites
- Blind persons can have higher values
- Vegetarians often have lower values
Additional information
- The BUN/creatinine ratio should be between 10:1 and 20:1.
- Creatinine level should always be checked before administering nephrotoxic agents, such as:
- Aminoglycosides
- Amphotericin
- Cisplatin
- Contrast (IV)
- Cyclophosphamide
- Methotrexate
- Mithramycin
- Semustine
- Vancomycin
- This test has been largely replaced by CPK measurements to reflect skeletal muscle necrosis and dystrophies
- Drugs and substances interfering in the spectrophotometric method include:
- 5-Fluocytosine
- Cephalosporins
- Ketones
- Lidocaine
- Related laboratory tests include:
Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.
Note:
A normal serum creatinine level does not rule out the presence of impaired renal function.
| Conv. Units (mg/dL) | SI Units (µmol/L) | |
|---|---|---|
| Adult Men | 0.7-1.4 | 62-124 |
| Adult Women | 0.5-1.1 | 44-97 |
| Pregnant women | 0.4-0.7 | 35-62 |
| Child 3-18 yrs | 0.3-1.0 | 27-88 |
| Child <3 yrs | 0.2-0.7 | 18-62 |
| Newborn | 0.3-1.0 | 27-88 |
| Critical levels for a non-dialysis patient are: |  10 | 884 |
BUN/Cr ratio typically 10-20:1
Elevated creatinine levels are associated with the following conditions:
- Anything that impairs renal function
- Burns
- Chronic nephritis
- Congestive heart failure
- Dehydration (Should have BUN:Cr ratio 20:1)
- Exercise (High levels)
- Hyper or Hypothyroidism
- Infections (Acute)
- Ketotic state (dieting, dehydration, diabetic)
- Leukemia
- Meat ingestion (Large amts)
- Muscle disease
- Acromegaly
- Amyotrophic lateral sclerosis
- Dermatomyositis
- Gigantism
- Muscular dystrophy
- Myasthenia gravis
- Poliomyelitis
- Obstructive uropathy
- Rhabdomyolysis
- Shock
- Systemic Lupus Erythematosus
Increased ratio BUN:Cr (20:1) with normal creatinine level occurs in the following:
- Catabolic states with tissue breakdown
- Congestive Heart failure
- Dehydration
- Gastrointestinal bleeding (Upper)
- Salt depletion
- Impaired renal function plus excess protein intake, production, or tissue breakdown
Increased ratio (>20:1) with elevated creatinine level occurs in the following conditions:
- Dehydration; Severe
- Obstructive uropathy
- Prerenal azotemia with renal disease
Drugs and substances that increase creatinine levels include:
- ACE inhibitors
- Acetaminophen (overdose)
- Acetohexamide
- Acetylsalicylic acid
- Acyclovir
- Albendazole
- Aldesleukin
- Alkaline antacids
- Alprostadil
- Altretamine
- Amiloride
- Aminoglycoside antibiotics
- Amiodarone
- Amphotericin B
- Angiotensin II Receptor Blockers
- Arginine
- Arsenicals
- Ascorbic acid
- Asparaginase
- Aspirin
- Azathioprine
- Azithromycin
- Aztreonam
- Barbiturates
- Benzodiazepines
- beta blockers
- Bicalutamide
- Capreomycin
- Carbamazepine
- Caspofungin
- Cephalosporin antibiotics
- Cetirizine
- Chlorothiazide
- Chlorpropamide
- Chlorthalidone
- Cidofovir
- Cinoxacin
- Cisplatin
- Clarithromycin
- Clofibrate
- Clonidine
- Clorazepate
- Colistimethate
- Colistin
- Co-trimoxazole
- Cyclosporine
- Danazol
- Demeclocyclinel
- Dextran
- Disopyramide
- Diuretics
- Doxorubicin
- Doxycycline
- Enflurane
- Epoetin alfa
- Ethambutol
- Etidronate
- Etretinate
- Flucytosine
- Fludarabine
- Fluoroquinolone antibiotics
- Foscarnet
- Furosemide
- Gabapentin
- Gemcitabine
- Gemfibrozil
- Glycerin
- Griseofulvin
- Histamine-2 Blockers
- Hydralazine
- Hydrochlorothiazide
- Hydroxyurea
- Idarubicin
- Imipramine
- Immune globulin
- Interleukin alfa-2
- Isotretinoin
- Lamotrigine
- Lansoprazole
- Leuprolide
- Levodopa
- Lidocaine
- Lithium
- Lovastatin
- Mannitol
- Mefenamic acid
- Meropenem
- Mesalamine
- Methotrexate
- Methyldopa
- Methylprednisolone
- Mitomycin
- Mitoxantrone
- Moxalactam
- Mycophenolate
- Nalidixic acid
- Neomycin
- Nifedipine
- Nilutamide
- Nisoldipine
- Nitrofurantoin
- NSAIDS
- Olsalazine
- Oxaprozin
- Pamidronate
- Paromomycin
- Pegaspargase
- Penicillamine
- Penicillin Antibiotics
- Pentamidine
- Pentostatin
- Phenazopyridine
- Phosphorus
- Plicamycin
- Prednisone
- Propafenone
- Quinolone antibiotics
- Radiographic agents/IV Contrast
- Risperidone
- Salicylates
- Sargramostim
- Sevoflurane
- Streptokinase
- Streptozocin
- Sulfamethoxazole
- Sulfasalazine
- Sulfisoxazole
- Tacrolimus
- Tetracycline
- Thiazide diuretics
- Ticlopidine
- Tramadol
- Tretinoin
- Triamterene
- Trimethoprim
- Trimetrexate
- Ursodiol
- Vancomycin
- Vasopressin
- Venlafaxine
- Vitamin D
The following conditions and substances may give falsely high results:
- Acetoacetate
- Acetone
- ß-hydroxybutyrate
- Cephalosporins
- Diabetic ketoacidosis
- Glucose
- Pyruvate
-ketoglutarate
Decreased creatinine levels occur in the following conditions:
- Advanced/Severe liver disease
- Decreased muscle mass
- Amputees
- Cachetic or elderly patients
- Inadequate dietary protein
- Small stature
- Muscular dystrophy - advanced
- Myasthenia gravis
- Pregnancy
Decreased BUN:Cr ratio (<10:1) with decreased BUN occurs in the following conditions:
- Acute tubular necrosis
- Decreased urea synthesis as in severe liver disease or starvation
- Pregnancy
- Repeated dialysis
- Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
Decreased BUN:Cr ratio (<10:1) with increased creatinine occurs in the following conditions:
- Muscular patients who develop renal failure
- Phenacemide therapy
- Rhabdomyolysis
Drugs that decrease serum creatinine levels include:
- Amikacin
- Ascorbic acid
- Cannabis
- Captopril
- Citrates
- Dobutamine
- Dopamine
- Ibuprofen
- Interferon -2A
- Lisinopril
- Methyldopa
- Nicardipine
- Prednisone
- Terazosin
- Triazolam
- Tromethamine
- Valproic acid
- Zidovudine
Drugs/Substances that falsely decrease serum creatinine levels include:
- Dextrose
- Histidine
- Quinidine
- LabTestsOnline®. Creatinine. [Homepage on the Internet] ©2001-2006. Last reviewed on -June 22, 2005-. Last accessed on -October 26, 2006-. Available at URL: http://www.labtestsonline.org/understanding/analytes/creatinine/test.html
- Szeto et al. Extrapolation of reciprocal creatinine plot is not reliable in predicting the onset of dialysis in patients with progressive renal insufficiency. J Intern Med. 2003 Mar; 253(3): 335-42
- Van Biesen W et al. The importance of standardization of creatinine in the implementation of guidelines and recommendations for CKD: implications for CKD management programmes. Nephrol Dial Transplant. 2006 Jan; 21(1): 77-83. Epub 2005 Oct 12.
- Walker AM et al. Anemia as a predictor of cardiovascular events in patients with elevated serum Creatinine. J Am Soc Nephrol. 2006 Aug; 17(8): 2293-8. Epub 2006 Jul 12.
- Wang X et al. Validation of Creatinine-Based Estimates of GFR When Evaluating Risk Factors in Longitudinal Studies of Kidney Disease. J Am Soc Nephrol. 2006 Sep 20; [Epub ahead of print]
- Weisbord SD et al. Associations of Increases in Serum Creatinine with Mortality and Length of Hospital Stay after Coronary Angiography. J Am Soc Nephrol. 2006 Aug 23; [Epub ahead of print]