Glomerular filtration rate and creatinine in the blood or urine
Creatinine is a type of waste product that is produced by the muscles and excreted by the kidneys. The glomerular filtration rate is a measure of how much blood the kidney can purify in a given period. The glomerular filtration rate and amount of creatinine in the blood or urine indicate how well the kidneys are functioning.
| What is the purpose of this test? | Creatinine blood or urine tests and glomerular filtration rate tests are performed for the following reasons:
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| How to prepare? |
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| Reference values* |
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| Associated tests | Associated tests include the following:
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| How is it done? |
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| How long before I get the results? | Results are usually ready in a day. It may take longer to receive your results. |
** Urine creatinine, weight-based, 24 h specimen.
What does an abnormal test result mean?
Abnormal values may indicate the following:
- Acute or chronic renal failure
- Kidney damage caused by drugs or toxins
- Prostate problems, kidney stones, or urinary tract obstruction
- Reduced blood supply to the kidneys due to various factors, such as shock (arterial hypotension), dehydration, congestive heart failure, atherosclerosis, or diabetic complications
- High or low muscle mass
- Muscle injury
- Autoimmune or liver disease
Medications that may affect test results
Certain medications may affect test results. Here are a few examples:
- Certain immunosuppressants (e.g., tacrolimus, cyclosporine)
- Certain antibiotics (e.g., the aminoglycoside class)
- Certain blood pressure medications (e.g., diuretics)
- Non-steroidal anti-inflammatory drugs (e.g., ibuprofen, naproxen)
Factors that can interfere with test accuracy
Falsely high results
- Intense physical activity
- Creatine dietary supplements
- Diets rich in red meat
Falsely low results
- Blood creatinine:
- Significant loss of muscle mass
- Urine creatinine:
- Urine collected incorrectly
What you should know before going for this test
When you go in for a blood test or any other medical exam, it's always a good idea to bring a complete list of any prescriptions, over-the-counter medications, or natural health products you're taking. Unless otherwise advised, it's best to take your medications as usual on blood test days. If in doubt, don't hesitate to talk to your healthcare professional.
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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.