A creatinine test is a measure of how well the kidneys are doing their job of filtering waste from the blood.
Creatinine is a chemical left over from the energy-producing processes in the muscles. healthy kidneys filter creatinine from the blood. creatinine leaves your body as a waste product in urine.
A blood or urine creatinine measurement provides clues to help your doctor determine how well your kidneys are working.
why is it done
Your doctor or other health care provider may order a creatinine test for the following reasons:
- to make a diagnosis if you have signs or symptoms of kidney disease
- to screen for kidney disease if you have diabetes, high blood pressure, or other conditions that increase your risk of kidney disease
- to monitor treatment or progression of kidney disease
- to manage medication side effects which may include kidney damage or impaired kidney function
- to monitor the function of a transplanted kidney
- for adult men, 0.74 to 1.35 mg/dl (65.4 to 119.3 micromoles/l)
- for adult women, 0.59 to 1.04 mg/dl (52.2 to 91.9 micromoles/l)
- 18 to 29 years old: 78 to 161 ml/min/bsa
- 30 to 39 years: 72 to 154 ml/min/bsa
- 40 to 49 years: 67 to 146 ml/min/bsa
- 50 to 59 years: 62 to 139 ml/min/bsa
- 60 to 72 years: 56 to 131 ml/min/bsa
- for adult men, less than 17 mg/g
- for adult women, less than 25 mg/g
how do you prepare
A standard blood test is used to measure the levels of creatinine in the blood (serum creatinine). Your doctor may ask you not to eat (fast) the night before the test.
For a creatinine urine test, you may need to collect urine for 24 hours in containers provided by the clinic.
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For either test, you may need to avoid eating meat for a set period of time before the test. if you take a creatine supplement, you may need to stop using it.
what you can expect
For a serum creatinine test, a member of your health care team takes a blood sample by inserting a needle into a vein in your arm.
For a urine test, you will need to provide a single sample at the clinic or collect samples at home over 24 hours and return them to the clinic.
Blood or urine creatinine results are measured and interpreted in many ways, including the following:
serum creatinine level
Usually, creatinine enters the bloodstream and is filtered out of the bloodstream at a generally constant rate. the amount of creatinine in the blood should be relatively stable. An elevated creatinine level may be a sign of poor kidney function.
Serum creatinine is reported as milligrams of creatinine per deciliter of blood (mg/dl) or micromoles of creatinine per liter of blood (micromoles/l). the typical range for serum creatinine is:
glomerular filtration rate (GFR)
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The measurement of serum creatinine can also be used to estimate how quickly the kidneys filter the blood (glomerular filtration rate). Due to the variability of serum creatinine from person to person, GFR can provide a more accurate reading of kidney function.
The formula for calculating GFR takes into account the serum creatinine count and other factors, such as age and gender. a gfr score below 60 suggests kidney disease. the range of scores below 60 can be used to monitor treatment and disease progression.
creatinine clearance is a measure of how well the kidneys filter creatinine from the bloodstream to excrete it in the urine.
Creatinine clearance is usually determined from a creatinine measurement in a 24-hour urine sample and a serum sample taken during the same time period. however, shorter time periods can be used for urine samples. timing and collection of the urine sample is important.
Creatinine clearance is expressed in milliliters of creatinine per minute per body surface area (mL/min/bsa). the typical range for men, ages 19 to 75, is 77 to 160 mL/min/bsa.
The typical range, by age, for creatinine clearance in women is as follows:
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No standard measurements for older adults have been determined.
Results below the typical range for your age group may be a sign of poor kidney function or conditions that affect blood flow to the kidneys.
Another interpretation of the urine creatinine count is called the albumin/creatinine ratio. albumin is a protein in the blood. healthy kidneys don’t usually filter it from the blood, so there should be little or no albumin in the urine.
The albumin/creatinine ratio describes how much albumin is in a urine sample relative to how much creatinine is there. results are reported as the number of milligrams (mg) of albumin per gram (g) of creatinine. the results that indicate a healthy kidney are:
A higher than normal result may be a sign of kidney disease. in particular, the result may indicate a complication of diabetes called diabetic nephropathy or diabetic kidney disease.
Your doctor or other health care provider will discuss the results of a creatinine test with you and help you understand what the information means for a diagnosis or treatment plan.