CREA | Creatinine

Creatinine – one of the key indicators of glomerular filtration and kidney function. When the kidney's filtration function is impaired, the concentration of creatinine in the serum increases. Creatinine is formed in the muscles and, once in the blood, is filtered in the kidney glomeruli. The concentration of creatinine in a healthy person's serum is quite constant, as its excretion rate in the kidneys varies only by 10–15%, and its synthesis is proportional to muscle mass. Creatinine filtration depends on the number of functioning glomeruli. If the number of functionally active glomeruli decreases, then the concentration of creatinine in the serum increases. As glomerular filtration and muscle mass decrease approximately proportionally with age, the concentration of creatinine in the serum remains practically unchanged. The concentration of creatinine in the serum may vary between different individuals, but for each healthy person, it is quite a constant value at various time points. The main indications for determining creatinine are to assess glomerular filtration, the amount of functionally active glomeruli, and the severity of kidney disease.

Creatinine is a more specific kidney test, but it may not be as sensitive in some cases of kidney disease. Only when the serum creatinine concentration exceeds 250μmol/l can it be stated that the accompanying increase in urea concentration is associated with renal insufficiency.

Creatinine is the final product of creatine metabolism. The formation of creatinine in the body heavily depends on the total muscle mass. Therefore, if the patient's weight is very low, if they have been diagnosed with hypothyroidism, or another reason reducing the concentration of creatinine, this indicator may not fully reflect the filtration function of the kidneys.

Creatinine increases with kidney failure, urinary tract obstruction, increased muscle mass, muscle breakdown. Creatinine decreases with low muscle mass, muscle dystrophy, during pregnancy, and when taking corticosteroids.

Recommendations:

• It is recommended to perform prophylactically once a year, for disease diagnosis and treatment control, performed periodically as instructed by a doctor.
• The results of the test are influenced by medications, diet, fasting, kidney diseases (glomerulonephritis, pyelonephritis, acute tubular necrosis), urinary tract obstruction, diabetes, hyperthyroidism, pregnancy.
• Fasting for 8-12 hours is required before taking the test.