Creatinine forms as a waste product when the body metabolizes the proteins from the foods you eat. The body breaks protein down into creatine and then turns the creatine into creatinine. Decreased creatinine levels do not occur as often as increased creatinine levels, so doctors must examine the reasons for this condition and rule out the presence of serious medical conditions.
Testing
The creatinine blood test allows doctors to identify decreased levels of creatinine in the blood. Normal creatinine levels range from 0.8 to 1.4 mg/dL, according to Medline Plus. In some cases, doctors order the basic metabolic panel to check the amount of creatinine, electrolytes and other waste products in the blood. The basic metabolic panel checks the levels of glucose, calcium, sodium, potassium, carbon dioxide, chloride and blood urea nitrogen, another waste product, in the blood.
Significance
Decreased creatinine levels indicate a problem with muscle mass or a diet low in protein. Because the body produces creatinine during the breakdown of protein, less protein intake results in less creatinine in the blood.
Causes
Low creatinine levels usually occur due to decreased muscle mass. Causes of decreased muscle mass include muscular dystrophy and myasthenia gravis. Muscular dystrophy causes muscle weakness and muscle wasting. Myasthenia gravis causes weakness of the voluntary muscles. The weakness gets worse during physical activity. Prolonged inactivity also leads to decreased muscle mass because the muscles get weaker if not used regularly.
Considerations
Some people naturally have less creatinine in their blood than others. Since men have greater muscle mass than women, women with normal kidney function usually have lower creatinine levels. Pregnant women may also have low creatinine levels. Some medications affect the validity of creatinine blood tests. Let your doctor know if you take vitamin C supplements, cephalosporin antibiotics, cimetidine or diuretic drugs.
Complementary Testing
If you have decreased creatinine levels, your doctor may order the creatinine clearance test. This test checks the amount of creatinine in the urine. The Family Practice Notebook website notes that doctors order the creatinine clearance test for pregnant women, very young or very old patients, people with malnutrition, very underweight people, very overweight people and people who have skeletal muscle disorders or some form of paralysis. This test requires you to collect your urine during a period of 24 hours. Decreased creatinine clearance indicates kidney disease, while increased creatinine clearance occurs in cases of pregnancy or excessive exercise.
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