Creatinine – characteristics, testing, norms of creatinine in blood and urine. What is creatinine clearance?

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Creatinine is an organic chemical that is excreted by the kidneys. It occurs in blood serum and urine. It is a nitrogen compound and is a product of changes in skeletal muscles, so it is a product of metabolism. Creatinine is a marker that allows us to monitor kidney function. For this reason, we decided to check how to determine creatinine in the blood and urine, and what the creatinine clearance is.

What is creatinine?

A creatinine blood test measures the level of creatinine in the blood. Creatinine is a waste product that is formed when creatine in the muscles breaks down. Blood creatinine levels can provide your doctor with information about how your kidneys work.

Each kidney has millions of tiny blood filtering units called nephrons. Nephrons constantly filter the blood through a very small cluster of blood vessels known as the glomeruli. These structures filter waste products, excess water and other impurities from the blood. Toxins are stored in the bladder and then removed by urinating.

Creatinine is one of the substances that the kidneys eliminate from the body. Doctors measure blood creatinine levels to check kidney function. High creatinine levels may indicate that your kidney is damaged and not working properly.

Creatinine blood tests are usually performed along with several other laboratory tests, including a blood urea nitrogen test and a basic metabolic panel or comprehensive metabolic panel.

Creatinine concentration depends on gender (higher is observed in men), muscle mass and the amount of meat consumed. Eating meat in large amounts promotes an increase in creatinine levels.

Get your creatinine levels tested in test packages for men and women. On Medonet Market you will find the following packages:

1. Woman’s health check – diagnostic blood tests,
2. Prophylactic blood tests for men.

Creatinine – indications for testing creatinine levels

Creatinine level testing may be ordered mainly for the diagnosis of kidney disease, when symptoms such as:

1. fatigue and trouble sleeping,
2. loss of appetite
3. swelling of the face, wrists, ankles or abdomen
4. lower back pain near the kidneys
5. changes in the frequency of urination
6. high blood pressure,
7. nausea,
8. vomiting.

Creatinine levels are also tested for:

1. glomerulonephritis,
2. pyelonephritis,
3. prostate diseases, prostate enlargement,
4. obstruction of the urinary tract which may be caused by kidney stones,
5. reduced blood flow to the kidneys, which may be caused by congestive heart failure, diabetes or dehydration.

Creatinine should also be tested before a visit to a dietitian, for example, using the Test before consultation with a dietitian – home blood analysis.

In addition, creatinine levels are determined in patients prior to surgery (e.g. general surgery) and cardiac surgery. The test is also used before diagnostic tests that require contrast.

See: Find out who needs dialysis

Creatinine and other research

The following diagnostic tests may be an indication for creatinine testing:

1. Computed tomography with the use of contrast (e.g. angio-CT), 
2. Magnetic Resonance Imaging (MRI), 
3. Coronary angiography – it is performed in people with ischemic heart disease and in the course of a heart attack. The coronary arteries, which are the vessels that supply blood to the heart muscle, are exposed. 
4. Arteriography – contrast is given and individual arteries are visualized. Depending on the needs, arteries in the upper limb, lower limb, kidneys or brain can be visualized. 

It is also worth checking the creatinine level prophylactically using one of the test packages available on Medonet Market, for example the Preventive screening package – blood tests. These tests are offered by the uPatient company, which makes it possible to collect a blood sample in one of over 500 facilities in Poland or at the patient’s home.

Creatinine – how to prepare for the test?

For serum creatinine testing, you must come to the laboratory on an empty stomach, at least 8 hours after the last meal. The day before the examination, no physical activity should be undertaken. Blood is drawn once from a vein in the arm. Usually 1 day is expected for results.

Age and muscle mass also affect the plasma creatinine level (the greater the muscle mass, the higher the creatinine concentration; in debilitated people, creatinine levels are lowered). High creatinine levels are only detectable when the glomerular filtration rate is reduced by more than 50%.

The serum creatinine test allows the calculation of the glomerular filtration rate. The e-GFR calculation is performed in patients whose blood creatinine levels may be low, e.g. in the elderly and those with low muscle mass.

Urine creatinine testing can be troublesome, so you usually need a single voiding fluid. During this time, you must not engage in any physical activity that may distort your results.

Find out how to fully diagnose kidney disease and make a kidney profile.

Creatinine in blood and urine – norms

Creatinine norms usually depend on the laboratory where the test was performed. The measurement method also plays a key role. Importantly, even muscle mass affects the test result (the greater the muscle mass, the higher the creatinine concentration). Other factors affecting the test result are pregnancy or limb amputation.

Being pregnant, make sure to regularly perform preventive examinations, in which not only the creatinine level will be determined, but also other parameters that are important for the proper development of the child and the mother’s health. Buy Pregnancy tests – blood test package now at Medonet Market.

The accepted creatinine norms are: 0,6-1,3 mg / dl. The values ​​may vary depending on the method used for the determination and the type of equipment. In turn, Mr.the correct GFR standard according to the MDRD formula is: ≥ 90 ml / min / 1.73 m2. This applies to:

1. urine creatinine concentration in women: 800-1350 mg / day or 7-12 mmol / day, 
2. urine creatinine concentration in men: 1100-2000 mg / day or 10-18 mmol / day. 

The norms of creatinine concentration in the blood are as follows:

1. norms of creatinine concentration in women – 50-110 umol / l,
2. norms of creatinine concentration in men – 60-120 umol / l, 
3. norms of creatinine concentration in children under 5 years of age – 20-40 umol / l. 

High creatinine levels – interpretation of results

Increased creatinine values ​​may appear in the following cases:

1. acute renal failure: associated with increased blood creatinine levels and decreased urine output below 500 ml per day; 
2. Long-term kidney disease: persistence of abnormal test results and abnormal kidney function for 3 months or more; 
3. ketoacidosis; 
4. taking certain medications, e.g. tetracycline antibiotics; 
5. excessive production of creatinine may appear during exercise or in people suffering from gigantism. 

Low creatinine levels – how to interpret the results?

Low levels of creatinine in the blood and urine can mean:

1. indicates that the kidneys are functioning well (if the test shows normal, within the normal levels); 
2. creatinine below normal indicates malnutrition and muscle wasting; 
3. occurs in people with low muscle mass (e.g. fasting); 
4. occurs in pregnant women; 
5. applies to people taking steroids, e.g. anti-inflammatory drugs or diuretics.

Stages of kidney failure based on GFR (glomerular filtration rate)

The test of creatinine concentration is very often used to calculate the so-called creatinine clearance when renal failure is suspected. The value of calculated creatinine clearance is a close approximation of the glomerular filtration rate (GFR) and is a good indicator for the assessment of the filtration function of the kidneys.

1. PHASE 1: GFR> 90 ml / min: kidney disease with normal GFR, 
2. PHASE 2: GFR 60-89 ml / min: early CKD, 
3. PHASE 3: GFR 30-59 ml / min: moderate CKD, 
4. PHASE 4: GFR 15-29 ml / min: severe CKD, 
5. FAZA5: GFR <15 ml/min: schyłkowa postać PChN. 

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Creatinine clearance – what is the test?

The creatinine clearance test is an older test used to check kidney function. This test monitors how much of the waste product – creatinine – is filtered out by the kidneys.

The two-part creatinine clearance test consists of collecting urine for 24 hours and then collecting blood. These samples are then tested to see how much creatinine has been filtered through the kidneys in 24 hours. The test results will be used in a mathematical formula that determines your creatinine clearance. Creatinine clearance is one way to assess the glomerular filtration rate (GFR), or how well the kidneys filter the blood.

Creatinine clearance testing is no longer used very often. This study has been largely superseded by the estimated GFR (eGFR) equations using blood creatinine levels – meaning no 24-hour urine collection is needed.

For the daily collection of urine, you will need a clean vessel with a volume of 1-2 liters to collect urine from the entire day, as well as the first voiding on the next day. The collected liquid should be thoroughly mixed, and then part (100-200 ml) should be poured into a clean container. The described container must be returned to the laboratory, where blood is also collected.

Creatinine – the price of the study

Creatinine clearance costs about PLN 25, and the patient receives the results within 20 hours of the test. The price of a serum and urine creatinine test is also about PLN XNUMX. You do not need a referral for the examination.