The creatinine is a waste product of catabolic muscle metabolism to produce energy, that is, a by-product of the motor activity that they develop. This metabolite can be detected in laboratory tests in blood and urine. To a lesser extent, its presence in the blood is also due to the consumption of animal protein, especially red meat.
As a by-product of metabolic activity, creatinine is filtered by the kidneys to be excreted in the urine, being transferred from the muscles to the kidney suspended in the blood serum. If kidney malfunction occurs, in the glomerular filtration rate, creatinine raises or lowers your blood values; But, if it is a question of a metabolic problem, or of another nature, the opposite generally occurs, that is, the serum creatinine values fall to levels below the standards considered normal, which indicates the possible presence of some other conditions that alter health, and may be different from kidney-type dysfunction.
Let’s first review what is considered a normal condition in blood creatinine values, and then move on to considerations about the causes and consequences of low blood creatinine values.
Standard values of creatinine in blood serum
Urine and serum creatinine quantification tests
- As part of the routine tests in a laboratory examination, direct determinations of creatinine levels are usually included, both in urine and in blood.
- The total amount of creatinine in the blood generally depends on the amount of muscle tissue that the individual owns; therefore, it varies between men and women, it also varies with age, and is higher in people who perform intense physical activities.
- The most common test is usually the urine creatinine, since its reduction is a direct suspicion of a kidney function problem, while it accumulates proportionally in the blood, so many times doctors request to complement the test with the serum creatinine, in order to complete what is known as the creatinine clearance test, by proportional comparison of the values of this metabolite in blood versus urine in a 24-hour period.
- Another complementary test involving creatinine values is possible; known as BUN: creatinine, which is the ratio of the proportion in blood between the amount of urea nitrogen (from the breakdown of proteins in the liver) and creatinine.
Normal serum creatinine values
- Values that are considered “normal” for serum creatinine may vary slightly from lab to lab, despite follow international standards generally. The absolute value of serum creatinine concentration obtained in the blood test should be evaluated by the doctor in the vicinity of the values of some other blood indicators.
- In general, normal blood creatinine values in adult men range from 0.6 to 1.4 mg / dL (53-107 µm / L).
- In adult women it is somewhat lower, ranging between 0.5 and 1.1 mg / dL (44-97 µm / L).
- Children from the age of three and adolescents from 18 have normal values similar to those of women, between 0.5 and 1.0 mg / dL.
- In children under three years of age, normal values can range from 0.2 to 0.7 mg / dL.
Factors affecting serum creatinine test values
- Have made intense physical activity up to two days before the blood test is done.
- Have eaten more than 8 ounces (230 grams) of meat (especially red meat) during the 24 hours prior to a creatinine determination and / or a creatinine clearance test.
- Being under medical treatment for use of some antibiotics, such as the cephalosporin known as cefoxitin and tetracycline.
- Be under diuretic treatment.
- Consume high doses of vitamin C.
- Be in treatment with antifungals Amphotericin B, Phenotoin, or Cimetidine.
- Being on treatment with quinine, quinidine, procainamide, trimethoprim, or methyldopamine.
- The pregnancy.
Meaning of low blood creatinine values
Results below standard values for serum creatinine may be indicating:
- Pregnancy. Women during their pregnancy period usually have a transient reduction in blood creatinine levels.
- Old age with poor muscle development; especially in women, it occurs progressively from the moment it begins menopause.
- Reduction of muscle mass.
- Protein deficit in the diet.
- Muscular dystrophy.
- Severe liver disease
- Heart failure.
- Congenital myotonia, which is a generalized condition of lack of all muscular that one is born with.
- Myasthenia gravis, which is a disease where there is a deficit in the delivery of nerve impulses to the muscles and therefore these tend to lose muscle tone.
- Rhabdomyolysis, which is a disease in which nerve fibers are degraded due to an autoimmune condition.
- Hepatic cirrhosis.
- Syndrome of inappropriate antidiuretic hormone secretion (SIADH), which is sometimes associated with some types of cancer and with kidney and liver deficiencies.
- Secondary disorders derived from the use of some medications.
How to help the body raise serum creatinine levels?
The diet can contribute to creatinine leveling up to minimum values of the normal range, when the blood serum concentration of creatinine is consistently low.
Among the foods that are required to be incorporated or increased in the diet, we have:
- Meats red and white.
- Fish, especially blue fish.
- High-value vegetable proteins, such as chickpeas, soybeans and moringa.
- Vegetables rich in potassium and magnesium, like bananas, potatoes, spinach, broccoli.
- Dairy products such as yogurt, labne, kefir (from milk), cured and fresh cheeses, fresh milk.