From the Guidelines
Chronic low serum creatinine is primarily caused by decreased muscle mass, as creatinine is a breakdown product of muscle metabolism, with common causes including advanced age, malnutrition, and muscle wasting diseases. The factors affecting serum creatinine levels are multifaceted, and it is essential to consider them when interpreting creatinine results. According to the study published in Kidney International 1, factors having a chronic effect on creatinine include:
- Chronic ‘reduction’ in creatinine:
- Low dietary protein (cooked meat) intake
- Reduced creatinine generation with lower muscle mass
- old age and female sex
- muscle-wasting conditions
- amputation
- malnutrition and critical illness These factors can lead to a decrease in serum creatinine levels, making it essential to consider them when evaluating kidney function. Additionally, the study published in Annals of Internal Medicine 1 highlights the importance of not relying solely on serum creatinine concentration to assess kidney function, as it can be affected by various factors such as creatinine secretion and generation, and extrarenal excretion. It is crucial to consider these factors and use a combination of serum creatinine measurement and estimated glomerular filtration rate (GFR) to accurately assess kidney function.
From the Research
Causes of Chronic Low Serum Creatinine
- Low skeletal muscle mass is a significant factor contributing to chronic low serum creatinine levels, as creatinine generation is reduced in individuals with low muscle mass 2, 3, 4, 5, 6.
- Malnutrition can also lead to low serum creatinine levels, as it is associated with reduced muscle mass and increased mortality in hospitalized patients, especially in intensive care unit (ICU) settings 2, 5, 6.
- Other factors that can influence serum creatinine levels include age, diet, exercise, stress, pregnancy, and kidney disease, which can affect creatinine generation and excretion 2, 3, 4, 5.
- Chronic kidney disease (CKD) can also contribute to low serum creatinine levels, as muscle wasting is a common complication associated with deteriorated renal function 3, 4, 5.
- Dietary meat intake can also impact serum creatinine variability, and biomarkers such as creatine, carnitine, carnosine, and others may be useful in adjusting for dietary influences on serum creatinine levels 3.