What is the meaning of low Creatinine (Cr) level?

From the Guidelines

Low creatinine levels are a significant indicator of decreased muscle mass or poor nutrition, and individuals with these levels should be evaluated for protein-energy malnutrition and wasting of skeletal muscle. Normal creatinine ranges are approximately 0.7-1.3 mg/dL for men and 0.6-1.1 mg/dL for women. Low creatinine values (below these ranges) are often seen in elderly individuals with muscle wasting, people with malnutrition, liver disease, or pregnancy. According to the study by 1, individuals with low predialysis or stabilized serum creatinine (less than approximately 10 mg/dL) should be evaluated for protein-energy malnutrition and wasting of skeletal muscle.

Key Points to Consider

• Low creatinine levels can be associated with increased mortality rates, as suggested by 1, and therefore, it is crucial to address the underlying cause.
• The body produces creatinine as a waste product from normal muscle metabolism, so individuals with less muscle mass naturally produce less creatinine.
• A low creatinine index and, in the absence of substantial endogenous urinary creatinine clearance, a low serum creatinine concentration suggest low dietary protein intake (DPI) and/or diminished skeletal muscle mass, as stated in 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, as outlined in 1.

Recommendations

• If you have low creatinine levels, your healthcare provider may evaluate your overall health, nutritional status, and muscle condition.
• In some cases, they might recommend dietary changes or exercise to improve muscle mass, especially if the low creatinine is related to malnutrition or muscle wasting.
• It is essential to consider the factors that can affect serum creatinine interpretation, as discussed in 1, to ensure accurate diagnosis and treatment.

From the Research

Definition of Low Creatinine

• Low creatinine levels can be an indicator of low muscle mass, also known as sarcopenia 2, 3, 4.
• Serum creatinine is a marker of muscle mass, and low levels can be associated with deterioration of bone mineral density 3.
• A low serum creatinine level is defined as below 0.88 mg/dl in men and 0.75 mg/dl in women, according to a study published in PloS one 3.

Relationship between Creatinine and Muscle Mass

• Serum creatinine reflects muscle mass, and low serum creatinine is independently associated with low bone mineral density in subjects with normal kidney function 3.
• The serum creatinine to cystatin C ratio can predict skeletal muscle mass and strength in patients with non-dialysis chronic kidney disease 5.
• Serum creatinine can serve as a biomarker of skeletal muscle mass in human subjects, especially in patients with chronic kidney disease 6.

Clinical Implications

• Low creatinine levels can be a prognostic marker for morbidity and mortality in different clinical settings where sarcopenia plays a significant role 4.
• The assessment of skeletal muscle mass and strength is important in clinical settings, and serum creatinine can be a useful marker for this purpose 5.
• Further studies are needed to extend the findings on the relationship between creatinine and muscle mass, and to explore the potential applications of serum creatinine as a biomarker in clinical practice 5, 6.