Creatinine is the product of creatine degradation, an amino acid produced by the liver and used by the muscles. This organic waste then passes into the blood and is eliminated by the kidneys through the urinary tract.

THE creatinine dosage present in the blood is carried out using a blood sample and is called serum creatinine. “It is a routine examination which is – among other things – offered as part of complete health check-ups” indicates the specialist. The sample is generally taken from the bend of the elbow. It is recommended, the day before the examination, not to practice intense physical exercise, to avoid consuming red meat (very rich in creatine) and to avoid products – drinks or food – diuretics.

The level of creatinine in the blood depends on several parametersof which mainly muscle mass “the more muscular you are, the more creatine you degrade and therefore the higher the amount of creatinine in the blood” explains the urologist, which makes it difficult to interpret this figure.
To assess renal function more reliably, we calculate, from the serum creatinine level, the GFR (DFG) also called serum creatinine clearance.

Serum creatinine clearance or GFR is considered the most accurate parameter to assess kidney function. It corresponds to the volume of plasma filtered by the kidneys per unit of time and is correlated with the functional nephrotic mass.
The GFR is calculated using a mathematical formula including – in addition to serum creatinine – parameters specific to each person: age, sex, weight, ethnicity, etc.
Several GFR calculation methods exist, but the three most frequently used are:

• Simplified MDRD formula (2006),
• CKD-EPI formula (2009),
• The formula of Cockcroft and Gault (1976), which is used less and less

Normal blood creatinine values ​​therefore depend on many factors, mainly muscle mass and gender. Overall, the standards are considered to be around:

– 5 to 10mg/L for a women
– 6.5 to 12mg/L for a male.

But it is the calculation of the clearance which will give the most precise indications on the functioning of the kidneys. And remember that the higher the creatinine, the lower the clearance :

– A GFR of less than 90 ml/min/1.m73² is considered normal.

– A GFR of between 60 and 90 ml/min/1.m73²: is the sign of a slightly too high serum creatinine, which requires additional examinations.

– Below 60 ml/min/1.m73², the GFR is too low: it is considered that there is a chronic kidney disease (CRD).

He is very rare that the serum creatinine is too low. “This can happen when the muscle mass is abnormally low, in the case of muscular dystrophy for example or in people in wheelchairs” indicates Dr. Dominique. Liver damage can also lower blood creatinine levels. Finally, elderly people suffering from muscle wasting as well as pregnant women may also have low serum creatinine.

A rise in serum creatinine is a sign of impaired kidney functionwhich can have a number of causes:

• The dehydration,
• An infection,
• kidney stones,
• chronic kidney disease,
• high blood pressure,
• A diabetes or pre-diabetes,
• heart failure,
• Rhabdomyolysis,
• Tobacco is recognized as a factor in the aggravation of kidney disease,
• physical exhaustion,
• A very high protein diet.

More than the creatinine level, it is the clearance calculation, or GFR, which is monitored and must alert.

– Between 15 and 30 ml/min/1.m73²we consider that therenal failure East severe,

To lower blood creatinine levels, the kidneys must be protected.

– Stay hydrated: by drinking at least 1.5 L of water a day,
– Balance diabetes,
– Identify the treatable cause of the increase in creatinine and treat it: “it can be by removing a stone or by treating an infection for example” explains Dr. Dominique,
– Treat hypertension,
– Treat any cardiac pathologies,
– Stop nephrotoxic drugs,
– Avoid eating too much salt: it is recommended not to consume more than 6g of salt per day ideally,
– Stop smoking,
– Limit the consumption of animal protein to one serving of meat/fish or eggs per day.