From the Guidelines
Creatinine levels outside the normal reference range of 60-110 μmol/L for men and 45-90 μmol/L for women are considered abnormal. When interpreting creatinine results, it's essential to consider individual factors like age, sex, muscle mass, and race, as these can affect baseline levels 1. Elevated creatinine often indicates reduced kidney function, as creatinine is a waste product filtered by the kidneys. Some key points to consider when evaluating creatinine levels include:
- Serum creatinine concentration is affected by factors other than GFR, such as creatinine secretion and generation and extrarenal excretion 1
- Clinical laboratories should report an estimate of GFR using a prediction equation in addition to reporting the serum creatinine measurement 1
- The trend in creatinine (or eGFR over months) is more important than the absolute value when monitoring renal function in the context of initiation and titration of drugs 1
- A patient-based monitoring regimen should be developed to rationalize guidance for monitoring of renal function and to minimize risk of WRF and AKI in vulnerable patients 1 Common causes of high creatinine include dehydration, kidney disease, certain medications (like NSAIDs, ACE inhibitors, or some antibiotics), muscle breakdown, or high protein diets. If abnormal creatinine levels are detected, further evaluation including estimated glomerular filtration rate (eGFR), urinalysis, and possibly kidney imaging may be necessary to determine the underlying cause and appropriate treatment. It is also crucial to understand that while an increase in serum creatinine over time suggests deterioration in renal function, it does not provide any information on the underlying renal pathology 1.
From the Research
Creatinine Reference Range
The normal reference range for creatinine in umol/L can vary depending on the laboratory and the individual's age, sex, and body size.
- However, a commonly cited reference range for adults is approximately 60-120 umol/L for males and 50-100 umol/L for females 2.
- It is essential to note that these values can vary, and the specific reference range used by a laboratory should be consulted when interpreting results.
Abnormal Creatinine Levels
Abnormal creatinine levels can indicate kidney dysfunction or disease.
- Elevated creatinine levels can suggest renal failure, and the degree of elevation can help determine the severity of the condition 3, 4.
- A systematic approach to evaluating elevated creatinine levels, including history, physical examination, and baseline tests, can help identify the underlying cause of renal failure 4.
- Accurate assessment of kidney function is crucial in the clinical setting, and various methods, including creatinine measurement, can contribute to the improvement of detection, monitoring, and treatment of chronic kidney disease 5.
Clinical Application
Understanding the physiology and clinical application of creatinine is critical in allowing accurate interpretation of creatinine values and translating them into changes in kidney function.
- Serum creatinine is the most widely used functional biomarker of the kidney, but its use is associated with substantial shortcomings 2.
- Alternative functional biomarkers of the kidney are being explored to improve the accuracy of kidney function assessment 2.
- The cumulative application of creatinine and urine output criteria can characterize renal excretory and fluid homeostatic dysfunction simultaneously, providing a more comprehensive description of the outcome implications of severe acute kidney injury 6.