Reasons you may not be able to
have the test or why the results may not be helpful include:
Taking medicines, such as methyldopa,
trimethoprim (Proloprim, Trimpex), vitamin C (ascorbic acid), cimetidine
diuretics, and cephalosporin antibiotics, especially
cefoxitin (Mefoxin). These affect the blood creatinine levels.
Taking medicines, such as
cimetidine (Tagamet), steroids, and tetracycline antibiotics. These can affect
the BUN-to-creatinine ratio.
Not collecting all your urine during the 24-hour urine collection test.
Doing strenuous exercise 2 days before
creatinine clearance test.
Eating more than
8 oz (227 g) of meat,
especially beef, in the 24 hours before a blood creatinine test and during a
creatinine clearance urine test.
What To Think About
A high blood creatinine level is generally seen
with a low creatinine clearance level because creatinine in the blood is
normally removed by the kidneys. If the kidneys are not able to remove
creatinine (low creatinine clearance), levels of creatinine in the blood go up
(high blood creatinine level).
If you are pregnant, your doctor can
check the amount of creatinine in
amniotic fluid to see how developed, or mature, your
baby's kidneys are. This can be helpful if there is a chance your baby will be
delivered early. A baby who has mature kidneys will make more creatinine than a
baby whose kidneys are still developing.
A normal blood creatinine
level does not rule out kidney disease. To help see whether kidney damage may
be present, a BUN level is also measured. Other tests may also be done to check
for kidney disease. For more information, see the topic
Blood Urea Nitrogen.
increase more slowly than blood urea nitrogen (BUN) levels, so an increase in
creatinine may mean chronic kidney problems.
glomerular filtration rate may be done for people with
chronic kidney disease to regularly check how well the kidneys are
Diabetes experts recommend that blood creatinine levels be
done every year for people with
diabetes. The creatinine level is used to find the
glomerular filtration rate, which shows how well the kidneys are
The amount of creatinine in the blood depends partly on
the amount of muscle tissue; blood creatinine levels are generally higher in
men than in women. Also, people who have large muscles, such as athletes,
normally have above-average blood creatinine levels.
urine sample to measure urine creatinine and sodium is sometimes done along
with blood creatinine and sodium levels to help find the fractional excretion
of sodium (FENA). This test can help your doctor see whether a problem with
blood flow to the kidneys is caused by dehydration or shock or by damage to the