Creatine is an important backup energy source for the body. It is typically not measured in the blood, but its breakdown product, creatinine, is regularly measured as one indicator of health. Creatine and creatinine blood levels are regulated by dietary intake, metabolism, and excretion. A health care professional should diagnose and manage problems with creatine or creatinine levels.
Intake and Synthesis
Creatine levels get into your blood through two sources: First is the diet. Red meat has a high concentration of creatine. Creatine is also available as a supplement at health and supplement stores. The second source of creatine is natural synthesis in the body. Creatine is synthesized in the kidneys and liver and travels through the blood to the tissues, where it is largely taken up by the nerves and muscles.
Metabolism
Once creatine is taken out of the bloodstream and into the target cells, an enzyme adds phosphate to the molecule to make creatine phosphate. Creatine phosphate is used to regenerate the main energy carrier of the cell, called adenosine triphosphate, or ATP. ATP consists of the base adenine, the sugar ribose, and three phosphate molecules. It releases energy by releasing one phosphate. Creatine phosphate donates its phosphate to rapidly regenerate the ATP. After creatine is used, it is broken down into creatinine.
Excretion
Creatinine travels through the blood to the kidneys. The kidneys are responsible for many functions in the body, particularly, regulating the composition of the blood. The kidneys help control blood pressure, blood volume, mineral content and filter water-soluble waste products, such as creatinine, into the urine.
Disorders
As the kidneys lose their ability to function, they filter less blood per minute. This results in changes to the blood content, including increased creatinine. As such, acute and chronic kidney disease raises the blood level of creatinine. Dehydration, blood loss, blockage of the urinary tract by a kidney stone, gout, or muscle problems can also increase the creatinine level. Some conditions, such as pregnancy, may also decrease the creatinine level.
References
- "Physiology"; Linda S.Costanzo; 4th Ed 2008
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar, et al.; 8th Ed 2009
