Creatinine levels and creatinine clearance (urine and blood)

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Urine and Serum Creatinine and Creatinine Clearance

Urine and Serum Creatinine and Creatinine Clearance

Why is this test performed?	Serum and urine creatinine, as well as creatinine clearance, are used to assess kidney function. Creatinine clearance is used, among other things, to detect early stage kidney disease, to adjust medication dosages and to monitor the adverse effects of certain medications on the kidneys.
How to prepare:	To measure urine creatinine Urine is collected over a 24-hour period (can be done over a shorter period). During the collection period, keep collected urine in a cool place. During the collection period, eat and drink normally and make sure that you are properly hydrated. To measure serum creatinine A regular blood sample is needed. There are no dietary restrictions prior to this test. Avoid vigorous physical exertion the day before and the day of the test.
Reference values:	Serum creatinine (women): 53 - 115 µmol/L Serum creatinine (men): 88 - 150 µmol/L Urine creatinine (women) : 6 - 13 mmol/24 hours Urine creatinine (men): 7 - 14 mmol/24 hours Creatinine clearance (women): 80 - 130 mL/min Creatinine clearance (men): 90 - 140 mL/min Creatinine clearance progressively decreases with age. Serum creatinine levels vary in children.
Related tests:	In addition to creatinine measurements, blood urea nitrogen levels are also measured. Normal values are between 2.5 and 8.2 mmol/L.

Note that target ranges may vary between laboratories.

General Information

Creatinine is a waste product that is produced by the muscles through normal contraction. Serum creatinine levels are fairly constant and proportional to muscle mass. Creatinine is excreted from the body through the kidneys. As a result, creatinine provides a good measure of how well the kidneys are working. An individual's creatinine clearance is determined using a mathematical calculation and the level of creatine in urine and in the blood. The resulting value indicates the amount of blood cleared of creatinine in one minute.

What does an abnormal test result mean?

If the result is too high

Creatinine clearance
A higher than normal creatinine clearance level can be indicative of anemia or increased blood flow to the heart.
Serum creatinine
The following factors can increase serum creatinine levels:
Acute or chronic kidney disorders
Dehydration
Decreased blood flow to the kidneys
Urinary tract obstruction
Severe muscle diseases
Complications of diabetes

If the result is too low

Creatinine clearance
A lower than normal creatinine clearance level may indicate that the kidneys are not working to their full capacity. It could also mean a low blood flow to the kidneys.
Serum creatinine
Low muscle mass, liver disease or muscle conditions may explain low serum creatinine levels.
Urine creatinine
Could indicate reduced kidney function.

Factors that can affect test results

Upward

Serum creatinine levels
The following can result in elevated serum creatinine levels:
Eating large amounts of meat before the test
Vigorous exercise
Certain drugs

Downward

Serum creatinine levels
Pregnancy and significant muscle loss (amputation, paralysis, etc.) are usually associated with decreased serum creatinine levels.
Urine creatinine levels
Improper urine collection can affect creatinine clearance or urine creatinine levels. Age is also associated with lower urine creatinine levels.

Certain drugs can affect serum and urine creatinine levels, including:

Aminosides (e.g. gentamicin (Garamycin®))
Amphotericin-B (Fungizone®)
Cephalosporins (e.g. Cefoxitin (Mefoxin®)
Cimetidine (Tagamet®)
Cisplatin (Platinol®)
Corticosteroids (e.g. Prednisone (Deltasone®))
Cyclophosphamide (Procytox®)
Erythromycin
Lithium (e.g. Carbolith®)
Mannitol (Osmitrol®)

Non-steroidal anti-inflammatories (e.g. Ibuprofen (Motrin®))
Methyldopa (Aldomet®)
Probenecid (Benemid®)
Quinine
Rifampicin (Rifadin®)
Tetracyclines
Trimethoprim (Proloprim®)
Vancomycin (Vancocin®)
Vitamin C

Furosemide (Lasix®)
Hydrochlorothiazide (Hydrodiuril®)
Indapamide (Lozide®), etc.

A mathematical formula is used to calculate creatinine clearance. Measurements may be biased in infants, the elderly, obese patients or those with low muscle mass.

What you need to know before the test

Before going for blood tests, a procedure or other exam, it is best to always bring a list of all the drugs you take (prescription, OTC and natural health products). Unless told otherwise, you should take your medication as usual on the day of the test. When in doubt, ask your pharmacist for more information.

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The patient information leaflets are provided by Vigilance Santé Inc. This content is for information purposes only and does not in any manner whatsoever replace the opinion or advice of your health care professional. Always consult a health care professional before making a decision about your medication or treatment.