What are the implications of low creatinine (serum creatinine) levels?

From the Guidelines

Low creatinine levels in the blood typically indicate decreased muscle mass or malnutrition rather than a primary medical concern, and addressing the underlying cause is crucial to improve overall health outcomes. According to the study published in Kidney International in 2015 1, factors that can cause a chronic reduction in creatinine include low dietary protein intake, reduced creatinine generation with lower muscle mass, old age, and female sex.

Implications of Low Creatinine Levels

• Decreased muscle mass or malnutrition are common causes of low creatinine levels
• Certain conditions associated with low creatinine include pregnancy, liver disease, muscle wasting disorders, and severe malnutrition
• Low creatinine itself rarely requires specific treatment, but identifying and addressing the underlying cause is essential
• If low creatinine is accompanied by other symptoms like unexplained weight loss, muscle weakness, or fatigue, a comprehensive evaluation by a healthcare provider is necessary

Recommendations for Managing Low Creatinine Levels

• Focus on improving overall nutrition with adequate protein intake (0.8-1.2g per kg of body weight daily)
• Consider a strength training program to build muscle mass
• Stay well-hydrated but avoid overhydration, which can further dilute creatinine levels
• A study published in Kidney International in 2020 1 highlights the importance of considering the clinical context and patient-centered approach when evaluating kidney function, which supports the need for a comprehensive evaluation in cases of low creatinine levels.

From the Research

Implications of Low Creatinine Levels

• Low serum creatinine levels have been associated with increased mortality in critically ill patients, independent of body mass index 2
• This association is thought to be due to the fact that serum creatinine is a surrogate marker of muscle mass, and low muscle mass is a risk factor for poor outcomes in critically ill patients 3, 2
• Low creatinine levels have also been linked to malnutrition and reduced skeletal muscle mass, which can negatively impact patient outcomes 3, 4
• In some cases, low creatinine levels may not have profound clinical significance, particularly in patients with low body mass or other underlying conditions 5
• Urinary creatinine excretion, which reflects muscle mass, has also been shown to be associated with short-term and long-term mortality in critically ill patients 4

Factors Influencing Creatinine Levels

• Serum creatinine levels can be influenced by multiple factors, including age, diet, exercise, stress, pregnancy, and kidney disease 3
• Dietary meat intake can also impact serum creatinine variability, and adjustment for this factor may be necessary when using serum creatinine as a muscle mass biomarker 6
• Kidney function and disease severity should also be taken into account when interpreting serum creatinine levels in critically ill patients 2, 4

Clinical Significance

• Low serum creatinine levels may indicate reduced muscle mass and increased risk of mortality in critically ill patients, highlighting the importance of monitoring and addressing malnutrition and muscle wasting in these patients 3, 2, 4
• Serum creatinine can serve as a reliable muscle mass biomarker if appropriate adjustment for kidney function and dietary meat intake is undertaken, making it a useful tool in clinical practice 6