Creatinine – Key Information
Creatinine is an organic chemical compound produced as a result of metabolic processes, mainly in the skeletal muscles, as a degradation product of creatine. Creatine is a key energy carrier in muscles, and approximately 1–2% of its total amount is broken down into creatinine each day. This compound is filtered by the kidneys and excreted in the urine, making it an important indicator of kidney function.
Creatinine Test
The laboratory test measuring creatinine levels is used to assess kidney function, diagnose kidney diseases, and monitor treatment. It is also essential before certain diagnostic procedures requiring contrast agents, such as computed tomography or magnetic resonance imaging.
The concentration of creatinine in the serum results from both production and excretion. It depends on muscle mass as well as the excretory function of the kidneys.
The test involves drawing blood from a vein, which is then sent to the laboratory for analysis. The entire procedure takes about 2–3 minutes, while the blood draw itself lasts several seconds. Improper preparation may lead to unreliable results. It is recommended to perform the test in the morning.
When Should You Test Creatinine Levels?
- before diagnostic tests using contrast (e.g., CT scan, MRI);
- preventively once a year, even without symptoms;
- when kidney damage is suspected, including acute or chronic kidney disease;
- when symptoms related to the urinary system occur;
- monitoring patients after kidney transplant;
- in cases of heart failure;
- monitoring hypertension;
- in diabetes;
- during treatment with neurotoxic substances or medications excreted by the kidneys (dose adjustment).
Symptoms that should prompt a creatinine test:
- hematuria, oliguria, or complete urinary retention;
- severe lower back pain;
- changes in the color or smell of urine;
- swelling around the ankles and face (under-eye puffiness);
- fever associated with kidney infections;
- nausea and vomiting;
- general weakness, fatigue, sleepiness;
- difficulty concentrating;
- dry and itchy skin;
- frequent urge to urinate.
High Creatinine
Elevated creatinine levels (above 1.3 mg/dl) often indicate impaired kidney function. Causes of high creatinine include:
- kidney failure,
- acute kidney injury,
- chronic kidney disease,
- low hydration levels or dehydration,
- intense physical activity,
- certain medications that may increase creatinine as a side effect.
Low Creatinine
Low creatinine levels (below 0.6 mg/dl) are generally not a cause for concern and often indicate normal kidney function. Causes may include:
- restrictive diets, especially low-protein diets;
- low muscle mass, especially in older adults or individuals with muscular dystrophy;
- use of certain medications, such as steroids or diuretics;
- pregnancy, due to glomerular hyperfiltration.
If low creatinine levels are detected, it is recommended to consult a doctor for an overall health assessment and possible additional testing.
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