Creatinin

An overview of creatinine, its role in the body, and its clinical significance

Creatinine is a chemical waste product that is produced by muscle metabolism and is excreted by the kidneys. It is a byproduct of the normal breakdown of muscle tissue and is typically produced at a fairly constant rate by the body, depending on muscle mass.

Biochemistry

Creatinine is formed from creatine, a molecule of major importance for energy production in muscles. Approximately 2% of the body's creatine is converted to creatinine every day. Creatinine is transported through the bloodstream to the kidneys, where it is filtered out and excreted in urine.

Clinical Significance

Creatinine levels in the blood and urine are important indicators of kidney function. The glomerular filtration rate (GFR), which is a measure of how well the kidneys are filtering blood, can be estimated using serum creatinine levels. This is because creatinine is filtered out of the blood by the kidneys and excreted in urine, with little to no reabsorption.

Serum Creatinine

Serum creatinine is a common blood test that measures the level of creatinine in the blood. Normal levels of serum creatinine vary depending on age, sex, and muscle mass. Elevated levels of serum creatinine may indicate impaired kidney function or kidney disease.

Creatinine Clearance

Creatinine clearance is a measure of the rate at which the kidneys are able to clear creatinine from the blood. It is calculated using the concentration of creatinine in a 24-hour urine sample and the serum creatinine level. Creatinine clearance is used to estimate the GFR.

Factors Affecting Creatinine Levels

Several factors can affect creatinine levels, including:

• Muscle mass: Individuals with more muscle mass tend to have higher creatinine levels.
• Diet: High protein intake can increase creatinine levels.
• Medications: Certain medications can affect creatinine levels.
• Hydration status: Dehydration can lead to elevated creatinine levels.

Interpretation of Results

Interpreting creatinine levels requires consideration of the individual's age, sex, and body size. It is also important to consider any medications or conditions that may affect kidney function. Persistent elevation of creatinine levels may warrant further investigation to assess kidney health.

Also see

• Kidney function tests
• Glomerular filtration rate
• Chronic kidney disease
• Acute kidney injury
• Urea