Creatinine Test - Creatine Urine Test

What Is Creatinine?

Creatinine is a waste product of creatine; an amino-acid contained in muscle tissue and found in urine. ¹  Creatinine is a chemical waste molecule that is generated from muscle metabolism. Creatinine is produced from creatine, a molecule of major importance for energy production in muscles. Approximately 2% of the body's creatine is converted to creatinine every day. Creatinine is transported through the bloodstream to the kidneys. The kidneys filter out most of the creatinine and dispose of it in the urine.

 

There are 2 main types of creatinine tests:

• Urine Creatinine Test

• Blood Creatinine Test

There are 2 main reasons for a creatinine test, to:

• Reveal important information about your kidneys

• Help determine if a urine test has been adulterated 

Because the muscle mass in the body is relatively constant from day to day, the creatinine level in the blood normally remains essentially unchanged on a daily basis.

What Is Adulteration? - Altered Urine Sample

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.

 

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.

 

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.

 

Urine Creatinine Test - 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:

 

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.

• Creatininene 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.

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.

Creatinine Reveals Important Information About Your Kidneys

What is creatinine?

Creatinine is a chemical waste molecule that is generated from muscle metabolism. Creatinine is produced from creatine, a molecule of major importance for energy production in muscles. Approximately 2% of the body's creatine is converted to creatinine every day. Creatinine is transported through the bloodstream to the kidneys. The kidneys filter out most of the creatinine and dispose of it in the urine.

Because the muscle mass in the body is relatively constant from day to day, the creatinine level in the blood normally remains essentially unchanged on a daily basis.

A creatinine test reveals important information about your kidneys.

Creatinine is a chemical waste product that's produced when you use your muscles or eat meat. Healthy kidneys filter creatinine and other waste products from your blood. The filtered waste products leave your body in your urine. If your kidneys aren't functioning properly, an increased level of creatinine may accumulate in your blood. A serum creatinine test measures the level of creatinine in your blood.

Creatinine can also be measured in your urine.

Because diabetes can damage the kidneys, regular creatinine tests are often recommended for people who have type 1 or type 2 diabetes. If you have kidney disease, creatinine tests can help your doctor monitor your condition. Creatinine tests can also impact your treatment plan, since several medications may not be safe to take if your kidneys aren't working well.

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 it 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 does the 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

• 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.

Why Get Tested?

To determine if your kidneys are functioning normally and to monitor treatment for kidney disease

When to Get Tested?

Routinely as part of a comprehensive or basic metabolic panel; if your doctor suspects that you are suffering from kidney dysfunction or if you are acutely or chronically ill with a condition that may affect your kidneys and/or be worsened by kidney dysfunction; at intervals to monitor treatment for kidney disease or kidney function while on certain medications

Creatinine and Creatinine Clearance

Creatinine and creatinine clearance tests measure the level of the waste product creatinine in your blood and urine. These tests tell how well your kidneys are working. The substance creatine is formed when food is changed into energy through a process called metabolism. Creatine is broken down into another substance called creatinine, which is taken out of your blood by the kidneys and then passed out of your body in urine. See a picture of the kidneys.

Creatinine is made at a steady rate and is not affected by diet or by normal physical activities. If your kidneys are damaged and cannot work normally, the amount of creatinine in your urine goes down while its level in your blood goes up.

Three types of tests on creatinine can be done:

Blood creatinine level

The blood creatinine level shows how well your kidneys are working. A high creatinine level may mean your kidneys are not working properly. The amount of creatinine in the blood depends partly on the amount of muscle tissue you have; men generally have higher creatinine levels than women.

Creatinine clearance test

A creatinine clearance test measures how well creatinine is removed from your blood by your kidneys. A creatinine clearance test gives better information than a blood creatinine test on how well your kidneys are working. A creatinine clearance test is done on both a blood sample and on a sample of urine collected over 24 hours (24-hour urine sample).

Blood urea nitrogen-to-creatinine ratio (BUN:creatinine)

The levels of blood creatinine and blood urea nitrogen (BUN) can be used to find the BUN-to-creatinine ratio. A BUN-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.

Urea is a waste product made when protein is broken down in your body. Urea is made in the liver and passed out of your body in the urine. A blood urea nitrogen (BUN) test measures the amount of urea in your blood. Like creatinine, it can help your doctor see how well your kidneys are working.

Why It Is Done

A blood creatinine level or a creatinine clearance test is done to see:

• if your kidneys are working normally.

• if your kidney disease is changing.

• how well the kidneys work in people who take medicines that can cause kidney damage.

• if severe dehydration is present. Dehydration generally causes BUN levels to rise more than creatinine levels. This causes a high BUN-to-creatinine ratio. Kidney disease or blockage of the flow of urine from your kidney causes both BUN and creatinine levels to rise.

How To Prepare

Do not do any strenuous exercise for 2 days (48 hours) before having creatinine tests.

Do not eat more than 8oz of meat, especially beef, or other protein for 24 hours before the blood creatinine test and during the creatinine clearance urine test.

It is important to drink enough fluids during the 24-hour urine collection but do not drink coffee and tea. These are diuretics that cause your body to pass more urine.

How It Is Done

Collection of the blood sample

The health professional drawing blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.

• Clean the needle site with alcohol.

• Put the needle into the vein. More than one needle stick may be needed.

• Attach a tube to the needle to fill it with blood.

• Remove the band from your arm when enough blood is collected.

• Put a gauze pad or cotton ball over the needle site as the needle is removed.

• Put pressure to the site and then a bandage.

Collection of the 24-hour urine sample

• You start collecting your urine in the morning. When you first get up, empty your bladder but do not save this urine. Write down the time that you urinated to mark the beginning of your 24-hour collection period.

• For the next 24 hours, collect all your urine. Your doctor or lab will usually provide you with a large container that holds about 1 gal (4 L). The container has a small amount of preservative in it. Urinate into a small, clean container and then pour the urine into the large container. Do not touch the inside of the container with your fingers.

• Keep the large container in the refrigerator for the 24 hours.

• Empty your bladder for the final time at or just before the end of the 24-hour period. Add this urine to the large container and record the time.

• Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.

How It Feels

Blood test

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Urine test

There is no pain while collecting a 24-hour urine sample.

Risks

Risks of a blood test

There is very little chance of a problem from having blood sample taken from a vein.

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.

• In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.

• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Urine test

There is no chance for problems while collecting a 24-hour urine sample.

Results

Creatinine and creatinine clearance tests measure creatinine levels in your blood and urine to give information about how well your kidneys are working. The creatinine clearance value is found from the amounts of creatinine in the urine and blood and from the amount of urine you pass in 24 hours. This value is the amount of blood cleared of creatinine per minute, based on your body size.

Normal

Normal results may vary from lab to lab.

Creatinine clearance values normally go down as you get older (normal values go down by 6.5 mL/min for every 10 years past the age of 20).

High values

• High creatinine blood levels. High creatinine blood levels can mean serious kidney damage or disease is present. Kidney damage can be caused by a life-threatening infection, shock, cancer, or low blood flow to the kidneys. Other conditions that can cause high blood creatinine levels include blockage of the urinary tract (such as by a kidney stone), heart failure, dehydration, excessive blood loss that causes shock, gout, or muscle conditions (such as rhabdomyolysis, gigantism, acromegaly, myasthenia gravis, muscular dystrophy, and polymyositis). Usually a high blood creatinine level means that the creatinine clearance value is lower than normal.

• High creatinine clearance. High creatinine clearance values can be caused by strenuous exercise, muscle injury (especially crushing injuries), burns, carbon monoxide poisoning, hypothyroidism, and pregnancy.

• High BUN-to-creatinine ratio. High BUN-to-creatinine ratios occur with sudden (acute) kidney failure, which may be caused by shock or severe dehydration. A blockage in the urinary tract (such as a kidney stone) can cause a high BUN-to-creatinine ratio. A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract or respiratory tract.

Low values

• Low blood creatinine levels. Low blood creatinine levels can mean lower muscle mass caused by a disease, such as muscular dystrophy, or by aging. Low levels can also mean some types of severe liver disease or a diet very low in protein. Pregnancy can also cause low blood creatinine levels.

• Low creatinine clearance. Low creatinine clearance levels can mean serious kidney damage is present. Kidney damage can be from conditions such as a life-threatening infection, shock, cancer, low blood flow to the kidneys, or urinary tract blockage. Other conditions, such as heart failure, dehydration, and liver disease (cirrhosis), can also cause low creatinine clearance levels.

• Low BUN-to-creatinine ratio. A low BUN-to-creatinine ratio may be associated with a diet low in protein, a severe muscle injury called rhabdomyolysis, pregnancy, cirrhosis, or syndrome of inappropriate antidiuretic hormone secretion (SIADH). SIADH sometimes occurs with lung disease, cancer, diseases of the central nervous system, and the use of certain medications.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking medicines, such as methyldopa, trimethoprim (Proloprim, Trimpex), vitamin C (ascorbic acid), cimetidine (Tagamet), some diuretics, and cephalosporin antibiotics, especially cefoxitin (Mefoxin). These affect the blood creatinine levels.

• Taking medicines, such as vitamin C (ascorbic acid), phenytoin (Dilantin), some cephalosporin antibiotics, captopril, aminoglycosides, trimethoprim (Proloprim, Trimpex), cimetidine (Tagamet), quinine, quinidine (Cardioquin, Quinaglute, Quinidex), procainamide, and the antifungal medication amphotericin B. These affect the creatinine clearance levels.

• Taking medicines, such as cimetidine (Tagamet), steroids, and tetracycline antibiotics. These can affect the BUN-to-creatinine ratio.

• Doing strenuous exercise 2 days before creatinine clearance test.

• Eating more than 8oz of meat, especially beef, in the 24 hours before a blood creatinine test and during a creatinine clearance urine test.

What To Think About

• A high blood creatinine level is generally seen with a low creatinine clearance level because creatinine in the blood is normally removed by the kidneys. If the kidneys are not able to remove creatinine (low creatinine clearance), levels of creatinine in the blood go up (high blood creatinine level).

• If you are pregnant, your doctor can check the amount of creatinine in amniotic fluid to see how developed, or mature, your baby's kidneys are. This can be helpful if there is a chance your baby will be delivered early. A baby who has mature kidneys will make more creatinine than a baby whose kidneys are still developing.

• A normal blood creatinine level does not rule out kidney disease. To help see whether kidney damage may be present, a BUN level is also measured. Other tests may also be done to check for kidney disease. For more information, see the medical test Blood Urea Nitrogen.

• Creatinine levels increase more slowly than blood urea nitrogen (BUN) levels, so an increase in creatinine may mean chronic kidney problems.

• A glomerular filtration rate may be done for people with chronic kidney disease to regularly check how well the kidneys are working.

• Diabetes experts recommend that blood creatinine levels be done every year for people with diabetes. The creatinine level is used to find the glomerular filtration rate, which shows how well the kidneys are working.

• The amount of creatinine in the blood depends partly on the amount of muscle tissue; blood creatinine levels are generally higher in men than in women. Also, people who have large muscles, such as athletes, normally have above-average blood creatinine levels.

• A one-time urine sample to measure urine creatinine and sodium is sometimes done along with blood creatinine and sodium levels to help find the fractional excretion of sodium (FENA). This test can help your doctor see whether a problem with blood flow to the kidneys is caused by dehydration or shock or by damage to the kidneys themselves.

Why is it important to check blood creatinine levels?

The kidneys maintain the blood creatinine in a normal range. Creatinine has been found to be a fairly reliable indicator of kidney function.

As the kidneys become impaired for any reason, the creatinine level in the blood will rise due to poor clearance by the kidneys. Abnormally high levels of creatinine thus warn of possible malfunction or failure of the kidneys. It is for this reason that standard blood tests routinely check the amount of creatinine in the blood. A more precise measure of the kidney function can be estimated by calculating how much creatinine is cleared from the body by the kidneys and it is referred to creatinine clearance.

What are "normal" blood creatinine levels?

Normal levels of creatinine in the blood are approximately 0.6 to 1.2 milligrams (mg) per deciliter (dl) in adult males and 0.5 to 1.1 milligrams per deciliter in adult females. (In the metric system, a milligram is a unit of weight equal to one-thousandth of a gram, and a deciliter is a unit of volume equal to one-tenth of a liter.)

Muscular young or middle-aged adults may have more creatinine in their blood than the norm for the general population. Elderly persons, on the other hand, may have less creatinine in their blood than the norm. Infants have normal levels of about 0.2 or more, depending on their muscle development. In people with malnutrition, severe weight loss, and long standing illnesses the muscle mass tends to diminish over time and, therefore, their creatinine level may be lower than expected for their age.

A person with only one kidney may have a normal level of about 1.8 or 1.9. Creatinine levels that reach 2.0 or more in babies and 10.0 or more in adults may indicate severe kidney impairment and the need for a dialysis machine to remove wastes from the blood.

What are the reasons for elevated blood creatinine?

Any condition that impairs the function of the kidneys will probably raise the creatinine level in the blood. It is important to recognize whether the process leading to kidney dysfunction (kidney failure, azotemia) is longstanding or recent.

The most common causes of longstanding kidney disease in adults are high blood pressure and diabetes mellitus. Certain drugs can sometimes cause abnormally elevated creatinine levels. Serum creatinine can also transiently rise after ingestion of large amount of dietary meat.

Are there any symptoms associated with elevated blood creatinine levels?

The symptoms of kidney dysfunction (renal insufficiency) vary widely. Some people may have a incidental finding of severe kidney disease and elevated creatinine on routine blood work without having any symptoms at all. In others, depending on the cause of problem, many different symptoms may be present including:

• feeling dehydrated,

• fatigue,

• shortness of breath,

• confusion, or

• many other nonspecific symptoms.

Creatinine is a chemical waste molecule that is generated from muscle metabolism. Creatinine is produced from creatine, a molecule of major importance for energy production in muscles. Creatinine has been found to be a fairly reliable indicator of kidney function. As the kidneys become impaired the creatinine level in the blood will rise. Normal levels of creatinine in the blood vary from gender and age of the individual.

Why it's done

A serum creatinine test — which measures the level of creatinine in your blood — can indicate whether your kidneys are working properly. How often you need creatinine tests depends on any underlying conditions and your risk of kidney damage. For example:

• If you have type 1 or type 2 diabetes, your doctor may recommend a creatinine test at least once a year.

• If you have kidney disease, your doctor may recommend creatinine tests at regular intervals to monitor your condition.

• Your doctor may recommend creatinine tests if you have an illness that may affect your kidneys or you're taking medication that may affect your kidneys.

How you prepare

The serum creatinine test is a common blood test. If your blood sample is being tested only for creatinine, you can eat and drink normally before the test. If your blood sample will be used for additional tests, you may need to fast for a certain amount of time before the test. Your doctor will give you specific instructions.

What you can expect

During the serum creatinine test, a member of your health care team simply takes a sample of blood by inserting a needle into a vein in your arm. The blood sample is sent to a lab for analysis. You can return to your usual activities immediately.

In some cases, your doctor may measure the level of creatinine in your urine as well. For this test, your doctor may ask you to collect 24 hours' worth of urine in a special container and submit it for analysis. The urine creatinine test can help your doctor more accurately assess the presence or degree of kidney failure.

Results

Results of the creatinine blood test are measured in milligrams per deciliter (mg/dL). The normal range for creatinine in the blood may be 0.6 to 1.2 mg/dL, although this can vary from lab to lab, between men and women, and by age. Since the amount of creatinine in the blood increases with muscle mass, men usually have higher creatinine levels than do women.

Generally, a high creatinine level means that your kidneys aren't working well. Your creatinine level may temporarily increase if you're dehydrated or you take certain medications — including some blood pressure drugs and nonsteroidal anti-inflammatory drugs, such as ibuprofen (Advil, Motrin, others). The dietary supplement creatine can have the same effect.

If your creatinine level is higher than normal, your doctor may want to confirm the results with another blood or urine test. If kidney damage is a concern, it's important to control any conditions that may be contributing to the damage. It's especially important to manage your blood pressure, which often requires medication. You can't undo permanent kidney damage, but with appropriate treatment you may be able to prevent further damage.