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Creatinine Test

What Is Creatinine?

Creatinine (from the Greek kreas, flesh) is a break-down product of creatine phosphate in muscle, and is usually produced at a fairly constant rate by the body (depending on muscle mass). Chemically, creatinine is a spontaneously formed cyclic derivative of creatine. Creatinine is chiefly filtered out of the blood by the kidneys, though a small amount is actively secreted by the kidneys into the urine. There is little-to-no tubular reabsorption of creatinine. If the filtering of the kidney is deficient, blood levels rise. Therefore, creatinine levels in blood and urine may be used to calculate the creatinine clearance (CrCl), which reflects the glomerular filtration rate (GFR). The GFR is clinically important because it is a measurement of renal function. However, in cases of severe renal dysfunction, the creatinine clearance rate will be "overestimated" because the active secretion of creatinine will account for a larger fraction of the total creatinine cleared. Ketoacids, cimetidine and trimethoprim reduce creatinine tubular secretion and therefore increase the accuracy of the GFR estimate, particularly in severe renal dysfunction. (In the absence of secretion, creatinine behaves like inulin.)

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A more complete estimation of renal function can be made when interpreting the blood (plasma) concentration of creatinine along with that of urea. BUN-to-creatinine ratio (the ratio of urea to creatinine) can indicate other problems besides those intrinsic to the kidney; for example, a urea level raised out of proportion to the creatinine may indicate a pre-renal problem such as volume depletion. A creatinine test may be ordered by a doctor or medical professional to determine various things. For more information, see Medical Use Creatinine In Urine - Creatinine Test. See also our section on Creatinine Blood Test.

Men tend to have higher levels of creatinine because they generally have more skeletal muscle mass than women. Vegetarians have been shown to have lower creatinine levels.

Plasma creatinine (PCr)

Measuring serum creatinine is a simple test and it is the most commonly used indicator of renal function.

A rise in blood creatinine levels is observed only with marked damage to functioning nephrons. Therefore, this test is not suitable for detecting early stage kidney disease. A better estimation of kidney function is given by the creatinine clearance test. Creatinine clearance can be accurately calculated using serum creatinine concentration and some or all of the following variables: sex, age, weight, and race as suggested by the American Diabetes Association without a 24 hour urine collection. Some laboratories will calculate the CrCl if written on the pathology request form; and, the necessary age, sex, and weight are included in the patient information. See also our section on Creatinine Blood Test.

Urine creatinine (UCr)

Creatinine concentration is also checked during standard urine drug tests. High creatinine levels indicate a pure test while low amounts of creatinine in the urine indicate a manipulated test, either through the addition of water in the sample or by drinking excessive amounts of water. For more information about creatinine and a drug test, see the "What is Adulteration" information below which discusses creatinine and drug testing.

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Interpretation

In the United States, creatinine is typically reported in mg/dL, while in Canada and Europe μmol/litre may be used. 1 mg/dL of creatinine is 88.4 μmol/L.

The typical human reference ranges are 0.5 to 1.0 mg/dL (about 45-90 μmol/L) for women and 0.7 to 1.2 mg/dL (60-110 μmol/L) for men. While a baseline serum creatinine of 2.0 mg/dL (150 μmol/L) may indicate normal kidney function in a male body builder, a serum creatinine of 1.2 mg/dL (110 μmol/L) can indicate significant renal disease in a frail old woman.

More important than absolute creatinine level is the trend of serum creatinine levels over time.

Creatinine levels may increase when ACE inhibitors (ACEI) or angiotensin-II receptor blockers (ARBs) are used in the treatment of erectile dysfunction (ED). Using both ACEI & ARB concomitantly will increase creatinine levels to a greater degree than either of the two drugs would individually. An increase of <30% is to be expected with ACEI or ARB use.

What is adulteration?

Adulteration is the tampering of a urine specimen with the intention of altering the test results. The use of adulterants can cause false negative results in drug tests by either interfering with the screening test and/ or destroying the drugs present in the urine. Dilution may also be employed in an attempt to produce false negative drug test results.

One of the best ways to test for adulteration or dilution is to determine certain urinary characteristics such as creatinine, pH, and specific gravity and to detect the presence of glutaraldehyde, nitrite and oxidants /pyridinium chlorochromate (PCC) in urine.

  • Creatinine is a waste product of creatine; an amino-acid contained in muscle tissue and found in urine.1 A person may attempt to foil a test by drinking excessive amounts of water or diuretics such as herbal teas to “flush” the system. Creatinine and specific gravity are two ways to check for dilution and flushing, which are the most common mechanisms used in an attempt to circumvent drug testing. Low creatinine and specific gravity levels may indicate dilute urine. The absence of creatinine (<5mg/dl) is indicative of a specimen not consistent with human urine.

  • Specific gravity tests for sample dilution. The normal range is from 1.003 to 1.030. Values outside this range may be the result of specimen dilution or adulteration.

  • Nitrite tests for commonly used commercial adulterants such as Klear or  Whizzies. They work by oxidizing the major cannabinoid metabolite THC-COOH.2 Normal urine should contain no trace of nitrite. Positive results generally indicate the presence of an adulterant.

  • Glutaraldehyde tests for the presence of an aldehyde. Adulterants such as UrinAid and Clear Choice contain glutaraldehyde which may cause false negative screening results by disrupting the enzyme used in some immunoassay tests.³ Glutaraldehyde is not normally found in urine; therefore, detection of glutaraldehyde in a urine specimen is generally an indicator of adulteration.

  • pH tests for the presence of acidic or alkaline adulterants in urine. Normal pH levels should be in the range of 4.0 to 9.0. Values outside of this range may indicate the sample has been altered.

  • Oxidants/PCC (Pyridinium Chlorochromate) tests for the presence of oxidizing agents such as bleach and hydrogen peroxide. Pyridinium chlorochromate (sold under the brand name UrineLuck) is a commonly used adulterant.³ Normal human urine should not contain oxidants or PCC.

Urine Specimen Validity Test (S.V.T.)

Description

#DUC-111 - One Step Specimen Validity Test (SVT) (25 tests per bottle).

Urine Adulteration Test Strips provide rapid, semi-quantitative detection of 7 parameters (Creatinine, Nitrite, Glutaraldehyde, pH, Specific Gravity, Oxidants / pyridinium chlorochromate (PCC) in human urine.

  • 7 testing parameters
  • Easy to interpret color chart
  • 2 year shelf life
  • 1 minute read time
 
Only  $17.95 each (bottle of 25).
Select Quantity:

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Medical Use - Creatinine In Urine

What does the medical creatinine test result mean?

Increased creatinine levels in the blood suggest diseases or conditions that affect kidney function. These can include:

  • damage to or swelling of blood vessels in the kidneys (glomerulonephritis) caused by, for example, infection or autoimmune diseases;

  • bacterial infection of the kidneys (pyelonephritis);

  • death of cells in the kidneys’ small tubes (acute tubular necrosis) caused, for example, by drugs or toxins;

  • prostate disease, kidney stone, or other causes of urinary tract obstruction; or

  • reduced blood flow to the kidney due to shock, dehydration, congestive heart failure, atherosclerosis, or complications of diabetes.

Creatinine can also increase temporarily as a result of muscle injury.

Low levels of creatinine are not common and are not usually a cause for concern. They can be seen with conditions that result in decreased muscle mass.

Creatinine levels are generally slightly lower during pregnancy.

NOTE: The result of your creatinine test is measured by your doctor against a reference range for the test to determine whether the result is “normal” (it is within the range of numbers), high (it is above the high end of the range), or low (it is below the low end of the range). Because there can be many variables that affect the determination of the reference range, the reference range for this test is specific to the lab where your test sample is analyzed. For this reason, the lab is required to report your results with an accompanying reference range. Typically, your doctor will have sufficient familiarity with the lab and your medical history to interpret the results appropriately.

While there is no such thing as a “standard” reference range for creatinine, most labs will report a similar, though maybe not exactly the same, set of numbers as that included in medical textbooks or found elsewhere online. For this reason, we recommend that you talk with your doctor about your lab results. For general guidance only, we are providing the reference range for this test from the classic medical text, Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. For more information on Creatinine in blood, see our section on Creatinine Blood Test.

Creatinine Test - One Step Specimen Validity Test (S.V.T.)

A rapid, one step screening test for the simultaneous detection of Creatinine, Nitrite, Glutaraldehyde, pH, Specific Gravity, and Oxidants/Pyridinium Chlorochromate (PCC) in human urine.

For forensic use only.

INTENDED USE

The One Step S.V.T. is a semi-quantitative, color comparison screen for the detection of creatinine, nitrite, glutaraldehyde, pH, specific gravity, and oxidants / pyridinium chlorochromate (PCC) in human urine.

This test provides a preliminary screen only. A more specific alternate chemical method must be used in order to obtain a confirmed analytical result. Abnormal results should be sent to a laboratory for confirmation.

SUMMARY

Each of the plastic strips contains six (6) chemically treated reagent pads. One (1) minute following the activation of the reagent pads by the urine sample, the colors that appear on the pads can be compared with the printed color chart on the canister. The color comparison provides a semi-quantitative screen for creatinine, nitrite, glutaraldehyde, pH, specific gravity, and oxidants / pyridinium chlorochromate (PCC) in human urine which can help assess the integrity of the urine sample.

PRINCIPLE

The test is based on the color derived from the chemical reaction between the chemical reagent on each test pad and the urine sample.

REAGENTS

Adulteration Pad Reactive indicator Buffers and non-reactive ingredients
Creatinine 0.04% 99.96%
Nitrite 0.07% 99.93%
Glutaraldehyde 0.02% 99.98%
pH 0.06% 99.94%
Specific Gravity 0.25% 99.7%
Oxidants / PCC 0.36% 99.64%

 

PRECAUTIONS

  • For forensic use only. Do not use after the expiration date.

  • The adulteration strips should remain in the sealed canister until use.

  • All specimens should be considered potentially hazardous and handled in the same manner as an infectious agent.
  • The used test strip should be discarded according to federal, state and local regulations.

STORAGE AND STABILITY

Store as packaged in the sealed canister at 15-30°C. The test strips must remain sealed in the canister until use. DO NOT FREEZE. Do not use beyond the expiration date. Avoid direct exposure to sunlight.

SPECIMEN COLLECTION AND PREPARATION
Urine Assay

The urine specimen must be collected in a clean and dry container. Test urine as soon as possible after collection.

Specimen Storage

For best results, test specimens immediately following collection. Storage of urine specimens should not exceed 2 hours at room temperature or 4 hours refrigerated (2-8°C) prior to testing.

MATERIALS

Materials Provided

  • Each canister contains 25 S.V.T. Strips

  • Package insert

Materials Required But Not Provided

  • Timer

DIRECTIONS FOR USE

  1. Allow the adulteration strip to equilibrate to room temperature (15-30 C) prior to testing.

  2. Remove the strip(s) from the canister and recap tightly.

  3. Dip test strip into the urine specimen and remove immediately..

  4. Blot the test gently on its side to remove excess urine. NOTE: It is important to blot the test strip for consistent results.

  5. Read results in one (1) minute by comparing each pad with the color chart printed on the canister. Do not interpret test results after 4 minutes.

  6. If the test indicates adulteration, refer to your Drug Free Policy for guidelines on handling adulterated specimens.

INTERPRETATION OF RESULTS

(Please refer to the illustration above)

Semi Quantitative results are obtained by visually comparing the reacted color blocks on the strip to the printed color blocks on the canister. No instrumentation is required.

Quality Control

Control standards are not supplied with this kit. However, it is recommended that positive and negative specimens or controls be tested as good laboratory practice to confirm the test procedure and to verify proper test performance.

LIMITATIONS

  1. The adulteration tests included with this product are meant to aid in the determination of abnormal specimens. While comprehensive, these tests are not meant to be an “all-inclusive” representation of possible adulterants.

  2. Creatinine: Normal creatinine levels are between 20 and 350 mg/dL. Under rare conditions, certain kidney diseases may show dilute urine.

  3. Nitrite: Nitrite is not a normal component of human urine. However, nitrite found in urine may indicate urinary tract infections or bacterial infections. Nitrite levels of > 20 mg/dL may produce false positive glutaraldehyde results.

  4. Glutaraldehyde: Is not normally found in urine. However certain metabolic abnormalities such as ketoacidosis (fasting, uncontrolled diabetes or high-protein diets) may interfere with the test results.

  5. Specific Gravity: Elevated levels of protein in urine may cause abnormally high specific gravity values.

  6. Oxidants/PCC: Normal human urine should not contain oxidants or PCC. The presence of high levels of antioxidants in the specimen, such as ascorbic acid, may result in false negative results for the oxidants/PCC pad.

BIBLIOGRAPHY OF SUGGESTED READING

  1. Tietz NW. Textbook of Clinical Chemistry. W.B. Saunders Company. 1986, 1734.

  2. Tsai, S.C. et.al., J. Anal. Toxicol. 1998; 22 (6): 474

  3. Cody, J.T., “Specimen Adulteration in drug urinalysis. Forsenic Sci. Rev., 1990, 2:63.

  4. Mikkelsen, S.L. et.al., Clin. Chem. 1988; 34: 648

  5. Hardman J, Limbird LE (Eds). Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 10th Ed., McGraw-Hill Publishing. 2001, 1010.

Creatinine Blood Test

How Is The Creatinine Blood Test Used?

The creatinine blood test is used along with a BUN (blood urea nitrogen) test to assess kidney function. Both are frequently ordered as part of a basic or comprehensive metabolic panel (BMP or CMP), groups of tests that are performed to evaluate the function of the body’s major organs. BMP or CMP tests are used to screen healthy people during routine physical exams and to help evaluate acutely or chronically ill patients in the emergency room and/or hospital. If the creatinine and BUN tests are found to be abnormal or if you have an underlying disease, such as diabetes, that is known to affect the kidneys, then these two tests may be used to monitor the progress of kidney dysfunction and the effectiveness of treatment. Blood creatinine and BUN tests may also be ordered to evaluate kidney function prior to some procedures, such as a CT (computed tomography) scan, that may require the use of drugs that can damage the kidneys.

A combination of blood and urine creatinine levels may be used to calculate a creatinine clearance. This test measures how effectively your kidneys are filtering small molecules like creatinine out of your blood.

Urine creatinine may also be used with a variety of other urine tests as a correction factor. Since it is produced and removed at a relatively constant rate, the amount of urine creatinine can be compared to the amount of another substance being measured. Examples of this are when creatinine is measured with protein to calculate a urine protein/creatinine ratio (UP/CR) and when it is measured with microalbumin to calculate microalbumin/creatinine ratio (also known as albumin/creatinine ratio, ACR). These tests are used to evaluate kidney function as well as to detect other urinary tract disorders.

Serum creatinine measurements (along with your age, weight, and gender) also are used to calculate the estimated glomerular filtration rate (eGFR), which is used as a screening test to look for evidence of kidney damage.

When Is A Creatinine Blood Test Ordered?

Creatinine may be ordered routinely as part of a comprehensive or basic metabolic panel, during a health examination. It may be ordered when you have non-specific health complaints, when you are acutely ill, and/or when your doctor suspects your kidneys are not working properly. Some signs and symptoms of kidney dysfunction include:

  • Fatigue, lack of concentration, poor appetite, or trouble sleeping

  • Swelling or puffiness, particularly around the eyes or in the face, wrists, abdomen, thighs or ankles

  • Urine that is foamy, bloody, or coffee-colored

  • A decrease in the amount of urine

  • Problems urinating, such as a burning feeling or abnormal discharge during urination, or a change in the frequency of urination, especially at night

  • Mid-back pain (flank), below the ribs, near where the kidneys are located

  • High blood pressure

The creatinine blood test may be ordered, along with BUN test and microalbumin, at regular intervals when you have a known kidney disorder or have a disease that may affect kidney function or be exacerbated by dysfunction. Both BUN and creatinine may be ordered when a CT scan is planned, prior to and during certain drug therapies, and before and after dialysis to monitor the effectiveness of treatments.

What Do The Creatinine Blood Test Results Mean?

Increased creatinine levels in the blood suggest diseases or conditions that affect kidney function. These can include:

  • Damage to or swelling of blood vessels in the kidneys (glomerulonephritis) caused by, for example, infection or autoimmune diseases

  • Bacterial infection of the kidneys (pyelonephritis)

  • Death of cells in the kidneys’ small tubes (acute tubular necrosis) caused, for example, by drugs or toxins

  • Prostate disease, kidney stone, or other causes of urinary tract obstruction

  • Reduced blood flow to the kidney due to shock, dehydration, congestive heart failure, atherosclerosis, or complications of diabetes

Creatinine blood levels can also increase temporarily as a result of muscle injury and are generally slightly lower during pregnancy.

Low blood levels of creatinine are not common, but they are also not usually a cause for concern. They can be seen with conditions that result in decreased muscle mass.

Levels of 24-hour urine creatinine are evaluated with blood levels as part of a creatinine clearance test.

Random urine creatinine levels have no standard reference ranges. They are usually used with other tests to reference levels of other substances measured in the urine. Some examples include the microalbumin test and urine protein test.

NOTE: The result of your blood creatinine test is measured by your doctor against a reference range for the test to determine whether the result is “normal” (it is within the range of numbers), high (it is above the high end of the range), or low (it is below the low end of the range). Because there can be many variables that affect the determination of the reference range, the reference range for this test is specific to the lab where your test sample is analyzed. For this reason, the lab is required to report your results with an accompanying reference range. Typically, your doctor will have sufficient familiarity with the lab and your medical history to interpret the results appropriately

While there is no such thing as a “standard” reference range for blood creatinine, most labs will report a similar, though maybe not exactly the same, set of numbers as that included in medical textbooks or found elsewhere online. For this reason, we recommend that you talk with your doctor about your lab results. For general guidance only, we are providing the reference range for this test below from the classic medical text, Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.

Is there anything else I should know?

Drugs such as aminoglycosides (vancomycin, gentamicin) can cause kidney damage and so creatinine is monitored. Other drugs, such as cephalosprins (cefoxitin), may increase creatinine concentration without reflecting kidney damage.

Remove the strip(s) from canister and recap tightly. Disclaimer: the information provided on this website should not be considered professional medical advice or medical counseling.  You should always consult your physician for any medical advice.

 

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