From the Guidelines
A creatinine level of 104 in urine with normal GFR and normal creatinine on CMP is generally not concerning, as indicated by studies such as 1, which suggests that serum creatinine concentration is affected by factors other than GFR.
Key Points to Consider
- Creatinine is a waste product from muscle metabolism that's filtered by the kidneys and excreted in urine.
- Urine creatinine levels can vary widely based on hydration status, muscle mass, diet, and time of collection.
- What's more important is your serum creatinine (measured in the CMP) and your calculated GFR, which you mention are normal, as supported by 1 and 1.
- This indicates your kidneys are functioning properly to filter waste products from your blood.
- The combination of normal serum creatinine, normal GFR, and the urine creatinine value suggests your kidneys are working effectively.
Recommendations
- No specific treatment or intervention is needed for this finding.
- Maintaining good hydration, following a balanced diet, and regular exercise are always beneficial for overall kidney health, as generally recommended in clinical practice.
- If you have other symptoms or concerns about kidney function, it would be appropriate to discuss these with your healthcare provider at your next visit, considering the guidelines provided by 1 and other relevant studies.
Important Considerations
- Clinicians should not use serum creatinine concentration as the sole means to assess the level of kidney function, as stated in 1.
- Clinical laboratories should report an estimate of GFR using a prediction equation in addition to reporting the serum creatinine measurement, as recommended in 1.
From the Research
Elevated Creatinine Levels and Normal GFR
- Elevated creatinine levels in urine, such as 104, can be caused by various factors, including muscle mass and creatine supplementation 2, 3.
- Studies have shown that creatine supplementation can increase creatinine levels, but it does not appear to have a significant impact on kidney function in healthy individuals 2, 3.
- However, individuals with pre-existing kidney disease or those at risk for kidney dysfunction should exercise caution when taking creatine supplements 2, 3.
Relationship Between Creatinine Levels and GFR
- The glomerular filtration rate (GFR) is a key indicator of kidney function, and creatinine levels are often used to estimate GFR 4, 5.
- However, creatinine levels can be influenced by factors such as muscle mass, age, and sex, which can lead to misclassification of kidney function 5, 6.
- Studies have shown that using alternative markers, such as cystatin C, can provide a more accurate estimate of GFR, especially in individuals with low muscle mass or muscle wasting 5, 6.
Clinical Implications
- Elevated creatinine levels with normal GFR results may not necessarily indicate kidney dysfunction, but rather other factors such as muscle mass or creatine supplementation 2, 3.
- Clinicians should consider using alternative markers, such as cystatin C, to estimate GFR, especially in individuals with extreme body composition or other factors that may influence creatinine levels 5, 6.
- Measured GFR using an exogenous marker, such as iohexol, can provide a more accurate assessment of kidney function in certain clinical scenarios 6.