2023-06-12 16:17:18
The creatinine is a metabolic waste whose quantities released vary according to the importance of the mass and the muscular activity. Creatinine is measured in the blood (creatinine) and in the urine (creatinineuria). The creatinine level indicates the state of renal filtration as well as the intensity of physical activity.
Definition: what is creatinine?
The creatinine is a creatine breakdown product, an amino acid found in muscle. Creatinine levels vary from one individual to another, but also according to different environmental factors.
A product of the breakdown of creatine
The creatinine is a product from dehydration of creatine and phosphocreatine. Approximately 2% of muscle creatine converts into creatinine daily.
Creatine is contained in the muscles constituting an energy reserve that can be used immediately.
The release of creatinine into the blood therefore increases when muscle mass or activity increases. Creatinine is then eliminated in the urine by filtration in the kidneys.
Serum creatinine: variable values
Serum creatinine varies from individual to individual depending on the state of muscle mass and kidney function. These values can still change depending on environmental factors such as diet, hydration, physical activity…
- Variations from one individual to another
From one individual to another, creatinine levels are variable. Their value is most often related to the state of the patient’s muscle mass and kidney function.
Individuals who have significant muscle mass generally have higher creatinine levels than others. This is why men often have higher serum creatinine levels than women. In addition, this explains why top athletes often have higher than average creatinine levels.
In addition, individuals who do not evacuate enough creatinine through the urine due to renal failure also have increased creatinine levels. This is the case for people with kidney failure.
- Unstable creatinine levels in the same individual
Finally, the creatinine level in the same individual is not constant. It varies according to:
- hydration status: dehydration can increase creatinine levels. It is therefore not recommended to measure serum creatinine in the event of fever or severe diarrhoea, for example.
- diet: the more the diet is rich in protein, the higher the creatinine levels are likely to be.
- physical activity: physical activity increases creatinine levels.
Why test for creatinine in the blood?
The creatinine blood test or creatinine is a useful analysis in nephrology since it represents a very good indicator of renal function (or more precisely of glomerular function).
Indeed, in case of kidney failure, the ability of the kidneys to eliminate waste products such as creatinine can decrease. These wastes then accumulate in the blood, result: the dosage of creatinine increases.
The blood creatinine test may be prescribed:
- whenthe doctor suspects kidney failure, especially when the patient has edema or high blood pressure. In this case, the creatinine assay is often associated with the albuminuria assay (search for protein in the urine), which is another marker of kidney damage.
- before carrying out certain radiology examinations requiring the use of iodinated contrast products eliminated by the kidneys. These products should be used with caution in case of renal insufficiency.
- in order to adapt the dosage of certain drugs that are strongly eliminated by the kidneys.
What is the normal blood creatine level?
The creatinine dosage is carried out by means of a blood test which does not require fasting.
A so-called “normal” blood creatinine level is between 5 to 14 mg/L. However, it should be noted that it tends to be higher in men than in women.
In addition to this, we also realize creatine clearance which measures the ratio between the rate of elimination of creatinine by the kidneys (through the urine) and its concentration in the blood. Since creatinine is eliminated only by renal filtration, the measurement of its clearance makes it possible to evaluate the filtration rate of the kidneys: the glomerular filtration rate or GFR.
The Haute Autorité de Santé recommends using first-line the formulated CKD-EPI from a serum creatinine assayed by enzymatic method, in order to measure the clearance of creatinine.
Creatinine clearance in women is between 80 and 130 mL/min.In humans, it is 90 to 140 mL/min. Creatinine clearance is reduced in renal insufficiency and its level is correlated with the severity of this insufficiency.
And glomerular filtration rate (GFR) normal is included between 90 and 120 ml/min/1.73 m2 (amount of blood plasma filtered per minute by the kidneys). A GFR less than 90 is therefore a sign of kidney failure. However, these results are interpreted differently depending on the age, sex and weight of the individual. Indeed, the elderly have a consistently lower GFR (from the age of 40, the GFR begins to decrease significantly).
Sometimes additional urine tests
In addition to the blood tests, the doctor may also request a urine analysis in order to measure the creatinine level in urine (creatinineuria) in order to make a more precise diagnosis. For this, the patient must collect his urine over a period of 24 hours.
In accordance with the indications noted on the analysis sheet, the results should normally be between 8 and 16 mmol/24 hours in women or 9 and 18 mmol/24 hours in men.
What creatinine level is worrying?
Creatinine levels (blood or urine) that are too high can be a sign of certain pathologies such as:
- A chronic renal failure. A GFR of less than 90ml/min/1.73m2 indicates renal failure. When the latter falls below 60ml/min/1.73 m2, it is a sign of more severe renal failure.
- The formation of kidney stones(or nephrolithiasis) related to the accumulation of mineral salts in the kidneys forming kinds of stones;
- The diabetes ;
- A high blood pressure ;
- of a autoimmune disease or infectious;
- And kidney cancer (plus rare).
Be careful, high creatinine levels are sometimes a sign of intense physical activity, dehydration or excessive protein consumption.
What are the symptoms of high creatinine?
The increase in creatinine does not cause any symptoms. On the other hand, the cause of this elevation can sometimes provoke certain manifestations. For example, the formation of kidney stones is particularly painful.
Unfortunately, increased creatinine, when it is a sign of impaired kidney function, does not cause symptoms. Kidney failure may be discovered late. Sometimes certain signs can appear over time such as intense fatigue, frequent urges to urinate, nausea, swelling of the feet…
What to do when creatinine increases?
The treatment of high creatinine is necessary when the cause is pathological.
In renal insufficiency, a follow-up in nephrology is necessary. Of the lifestyle measures are recommended first. Of the nephroprotective drugs may be prescribed in more advanced cases. In severe cases the dialysis even a kidney transplant (kidney transplant) can be considered.
Kidney stones can go away spontaneously or through surgery.
The other causes of high creatinine/creatinuria most often require specific treatment, whether it is diabetes (hygieno-dietetic measures, medications, etc.), arterial hypertension (taking anti-hypertensives, etc. .), autoimmune or infectious diseases…
In order to take care of your kidneys, it is recommended to:
- limit your consumption of meat and protein;
- drink enough (at least 1.5 liters per day) ;
- engage in regular physical activity;
- control his weight.
- smoking cessation for smokers.
Medical supervision is necessary in case of kidney disease (with regular blood tests).
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