<biochemistry> A compound which is made by the body and is used to store
energy in the form of phosphate molecules.
When phosphate molecules are attached to it, it is called creatine phosphate
and is capable of donating phosphate to ADP in order to make ATP. (ATP is the
molecule which is converted into ADP with a release of energy that the body
<biochemistry, nephrology> A waste product of protein metabolism that is
found in the urine.
Can be measured to assess overall kidney function. An abnormally elevated
blood creatinine level is seen in those individuals with kidney insufficiency and
So, the bottom line is that creatin is good for us, while creatine is not.
1. Serum Creatine and Normal Range
Creatine and its breakdown product, creatinine, play an important role in energy
metabolism. The body synthesizes creatine and derives it from food sources. It
enters cells to help provide energy before being broken down and excreted. The
level of blood serum creatinine and creatine can give clues about certain disease
states. It is important to consult a physician regarding elevated creatinine and the
diagnosis and management of other health-related conditions.
Creatine Blood Levels
In blood, the breakdown product of creatine, creatinine, is measured by
laboratory methods to help diagnose health conditions. Normal values are 0.6 to
1.0 mg/dL; however, it is possible to be slightly outside this range and still be
healthy. The level of creatinine in the blood represents the balance between the
production and use of creatine versus the excretion of creatinine.
Synthesis and Sources
Creatine is synthesized from the amino acids glycine, methionine and arginine in
the kidney and liver. It travels in the blood, primarily to the skeletal muscles. It is
also found in the diet, especially meats. Creatine supplements are also available.
When muscle contracts, it uses the energy-carrying molecule ATP to perform
work. ATP carries three phosphate groups on the molecule. When muscle
contracts, one phosphate is lost off of ATP, making ADP. Creatine carries
phosphate inside the muscle, and can quickly donate the phosphate to ADP,
replenishing ATP, which can then be used again for work.
Degradation and Excretion
Creatine is degraded into the structurally similar chemical creatinine. It is released
from the muscle cells back into the blood. The kidneys then filter creatinine from
the blood and excrete it into the urine.
There are a few diseases involving an inability of the body to synthesize creatine,
which largely results in nerve damage. The most common reason to find elevated
creatinine in the blood is decreased kidney function. Creatinine levels rise in
proportion to the loss of filtration capacity of the kidneys.
Supplementation with oral creatine supplements is common among athletes. The
effects on athletic performance are mixed in studies. A 2002 study published in
the "Journal of Family Practice" concluded that creatine supplementation with
resistance training increases the maximum weight lifted in young males under age
36. Furthermore, there is no evidence for enhanced performance in older persons
or women or for other types of power or strength exercises. Finally, the safety of
creatine remains unproven, and until these issues are addressed, its use cannot
be universally recommended.
"Physiology"; Linda S.Costanzo; 4th Ed 2008
"Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar et al.; 8th Ed 2009
"Molecular Biology of the Cell"; Bruce Alberts et al.; 4th Ed 2002
"Lehninger Principles of Biochemistry"; David L. Nelson and Michael M. Cox; 4th
"Journal of Family Practice"; "Does oral creatine supplementation improve
strength? A meta-analysis"; Dempsey RL, Mazzone MF, Meurer LN; 2002
1. Acceptable Creatinine Levels
Creatinine is included in most routine lab work because it is the most reliable
indicator of kidney health. Kidney patients should know what creatinine is, how it
is measured and what their creatinine values mean. Many patients find it helpful
to maintain a spreadsheet of their creatinine levels. This data provides insight into
how fast kidney disease is progressing.
Creatinine is a waste product produced by the muscles. It should not be confused
with creatine. Creatine is found in muscles. When muscles work hard, they
convert creatine into creatinine. <br /><br />Both blood urea nitrogen, or BUN,
and creatinine are nitrogenous wastes produced by the muscles. Unlike BUN,
creatinine levels remain relatively stable in healthy people.
Creatinine is measured in milligrams per deciliter (mg/dl) in the U.S. and in
micromoles per liter (?/l) in Europe and Canada. Check what units are being used
if a creatinine value seems impossibly high or low.<br /><br />Multiply by 88.4 to
convert between milligrams per deciliter to micromoles per liter. For example, a
creatinine value of 0.6 mg/dl is equivalent to 53.04 ?/l.<br /><br />Patients who
change medical providers should not be surprised if their lab results edge up or
down because there are slight variations in how labs measure creatinine. Such
changes are normal.
Men usually have higher creatinine values than women because they are more
muscular. Similarly, adults have higher normal values than children. <br /><br
/>According to the Family Practice Notebook, normal creatinine values for adult
males are between 0.8 and 1.3 mg/dl. Normal values for women are between 0.6
and1.0 mg/dl. Normal values for children are lower. They depend upon the age
and size of the child.
While there is no such thing as abnormally low creatinine levels, abnormally high
levels can be symptomatic of many kidney disorders ranging from diabetes,
glomerular disease, birth defects such as renal dysplasia and many other kidney
diseases. If creatinine levels are abnormally high on repeated tests, additional
diagnostic work will be necessary to determine the nature of the disorder. These
tests might include urinalysis, ultrasound and kidney biopsy.
Serum creatinine levels are different from urine creatinine levels. Urine creatinine
levels are used to calculate other values such as protein creatinine ratios or
calcium creatinine ratios. Urine creatinine levels should not be confused with
serum creatinine levels because taken alone, urine levels are not indicators of
disease.<br /><br />If serum creatinine levels are not normal, it is important to
get the test repeated before panicking. Many factors such as dehydration can
throw off an otherwise normal value.
BUN Vs. Serum Creatinine: Which Is Better for Renal
Normally, your kidneys screen impurities from your bloodstream. The result of
this process is the removal of waste materials and excess fluid in the urine.
Occasionally, infections, injuries and disease hamper the ability of the kidneys
to perform this process, resulting in renal insufficiency. To confirm a suspicion
of renal insufficiency requires evaluating test results together with signs and
symptoms to make a final diagnosis. Two important tests are the blood urea
nitrogen, or BUN, and the serum creatinine.
Creatinine, a waste material, comes from the breakdown of protein in your
body. The kidneys filter out the creatinine and eliminate it in the urine. The
portion of the kidneys that filters out the creatinine, called the glomerulus, is
susceptible to blood vessel problems and infections that cause more creatinine
to build up in the bloodstream. The serum creatinine blood test measures the
amount of creatinine in the bloodstream when the kidneys are unable to
remove it. An elevated serum creatinine reliably reflects renal insufficiency but
is taken into consideration with the urine creatinine clearance and blood urea
Blood Urea Nitrogen
Urea nitrogen comes from protein intake and the breakdown of protein in
tissues. Levels of urea nitrogen in the blood fluctuate with a number of
conditions such as increased protein intake, intestinal bleeding, infection, fever,
dehydration, medications and burns. The blood urea nitrogen test doesn't
indicate renal insufficiency as well as the serum creatinine, since changing
factors contributing to fluctuating values unrelated to kidney function may be
present. The BUN should be considered along with the serum creatinine test.
Some individuals who develop renal insufficiency exhibit few or mild symptoms
or the deficit in kidney function is noted during a yearly physical with no
obvious symptoms. In the extreme, an individual might present with extremely
high blood pressure, rapidly decreasing kidney function or frank kidney failure.
The insufficiency can result from decreasing arterial blood flow to the kidneys as
a consequence of renal artery disease. Renal artery stenosis, a narrowing of the
arteries caused by plaque formation, leads to renal artery disease. With the
reduction of blood delivered to the kidneys for screening and purifying, excess
body fluids and wastes build up, blood pressure rises and renal insufficiency
The risk factors for developing renal insufficiency include the aging process,
gender, race, high cholesterol and triglycerides, smoking and diabetes mellitus.
Additional contributing factors include a family history of renal disease, high
blood pressure and obesity. Individuals at even higher risk include those with a
diagnosis of coronary artery disease, peripheral vascular disease or