Biomarkers

Creatinine

Creatinine is an essential biomarker for evaluating kidney function. Understanding its role, its normal ranges, and how to manage its levels is crucial to maintaining kidney health and avoiding complications.

What is creatinine?

Creatinine is a waste product produced by normal muscle wear and tear. When converting food into energy, the body produces creatine, a molecule that is essential for muscle cells. Creatine is then broken down into creatinine at a relatively constant rate.

It is eliminated from the blood by the kidneys and then excreted in the urine. This process makes it a reliable indicator of kidney health.

Creatinine function

Creatinine has no active role in the body, but monitoring it is crucial to assess kidney health.

  • Healthy kidneys : Effectively filter creatinine, releasing it into the urine.
  • Damaged kidneys : Accumulate creatinine in the blood, indicating impaired filtration.

How do you test creatinine?

Test methods

  1. Blood Test (Serum Creatinine) :
    A blood test is the most common method for assessing creatinine levels and kidney function.
    • Included in a basic metabolic panel (BMP) Or a comprehensive metabolic panel (CMP).
    • A blood sample is taken, usually from the arm, and analyzed in the laboratory.
  2. Urine Test (24 Hour Urine Collection) :
    This test involves collecting all the urine produced over 24 hours for a complete analysis of kidney function.
    • Measures the total volume and quantity of creatinine excreted in the urine.

Preparations for the Test

  • Hydration : Maintain normal fluid intake.
  • Diet : Avoid meals that are high in protein (meat) before the test, as they may temporarily increase creatinine.
  • Physical Activity : Avoid strenuous exercise 24 hours before the test.
  • Medications : Tell your doctor about treatments or supplements taken.

Normal Creatinine Levels

In the blood

  • Adult men : 0.74 to 1.35 mg/dL (65.4 to 119.3 µmol/L).
  • Adult women : 0.59 to 1.04 mg/dL (52.2 to 91.9 µmol/L).

In the Urine

  • Hommes : 0.8 to 1.8 g/day (7 to 16 mmol/day).
  • Women : 0.6 to 1.6 g/day (5.3 to 14 mmol/day).

Normal ranges may vary depending on the laboratories and methods used.

Factors Influencing Creatinine Levels

Factors Increasing Levels

  • Meat-rich diet : Increases creatinine production.
  • Creatine Supplements : Contribute to a temporary increase.
  • Intense exercise : Causes increased muscle degradation.
  • High Muscle Mass : More common among bodybuilders.
  • Some medications : Like cimetidine, ritonavir, or trimethoprim.

Factors Reducing Levels

  • Vegetarian/Vegan Diet : Decreases creatinine production.
  • Low muscle mass : Common in the elderly or in cases of muscular atrophy.
  • Pregnancy : May lower levels due to increased blood flow.
  • Serious liver diseases : Reduce creatine synthesis.

Interpreting the Results

Creatinine levels should be interpreted by a health professional, who will take into account your overall condition, symptoms, and other tests to provide a comprehensive assessment.

Abnormal Creatinine Levels

High Creatinine Levels

Causes
  • Kidney disease : Chronic kidney failure (CKD) or acute renal failure (ARI) impedes creatinine filtration.
  • Dehydration : Reduces blood dilution, temporarily increasing levels.
  • High protein diet : Increases metabolic production.
  • Intense exercise : Causes a temporary increase.
Associated symptoms
  • Tiredness and weakness.
  • Oedemas (legs, ankles).
  • Changes in urinary habits (frequency or reduced volume).
  • Nausea and vomiting.
Implications
  • Kidney failure : May require dialysis or a transplant.
  • Hypertension : May worsen kidney damage.
  • Heart diseases : Kidney dysfunction increases cardiovascular risk.

Low creatinine levels

Causes
  • Reduced muscle mass : Common among the elderly.
  • Malnutrition : Causes a drop in production.
  • Severe Liver Disease : Affects creatine synthesis.
Associated symptoms
  • General weakness.
  • Weight loss.
  • Edemas in cases of serious liver diseases.
Implications
  • Muscular dystrophy : Progressive loss of muscle mass.
  • Hepatic disease : May cause numerous metabolic complications.

Related Complementary Tests

  • eGFR (Estimated Glomerular Filtration Rate) : Assesses overall kidney function using creatinine levels, age, gender, and other factors.
  • Creatinine Clearance Test : Combines blood and urine tests to accurately measure creatinine elimination.
  • Urea/Creatinine Ratio (BUN/Creatinine) : Detects renal or metabolic imbalances.
  • Cystatin C : An alternative marker for evaluating kidney function, less influenced by muscle mass.
  • Imaging (ultrasound, MRI) : Identifies structural abnormalities in the kidneys.
  • Managing and Improving Creatinine Levels

    Dietary changes

    • Reduce protein : Limit red meat to avoid metabolic overload.
    • Increase fiber : Promotes kidney health.
    • Drink Enough Water : Good hydration improves the elimination of waste.
    • Limit salt : Reduces blood pressure and protects the kidneys.

    Lifestyle Changes

    • Moderate exercise : Maintain physical activity without excess to maintain muscle and kidney health.
    • Avoid NSAIDs : Anti-inflammatory drugs may affect kidney function.
    • Monitor Blood Pressure : Essential for the prevention of chronic kidney damage.
    • Regular checks : Detect anomalies early through regular testing.

    Proactively managing creatinine levels can prevent serious complications and promote optimal kidney health.