test checks different components of urine, a waste product made by the
kidneys. A regular urine test may be done to help find
the cause of symptoms. The test can give information about your health and
problems you may have.
kidneys take out waste material, minerals, fluids, and
other substances from the blood to be passed in the urine. Urine has hundreds
of different body wastes. What you eat and drink, how much you exercise, and how
well your kidneys work can affect what is in your urine.
100 different tests can be done on urine. A regular
urinalysis often includes the following tests:
Color. Many things affect urine color, including
fluid balance, diet, medicines, and diseases. How dark or light the color is
tells you how much water is in it. Vitamin B supplements can turn urine bright
yellow. Some medicines, blackberries, beets, rhubarb, or blood in the urine can
turn urine red-brown.
Clarity. Urine is normally clear. Bacteria, blood,
sperm, crystals, or mucus can make urine look cloudy.
Odor. Urine does not smell very strong, but it has a
slightly "nutty" odor. Some diseases cause a change in the odor of urine. For
example, an infection with E. coli bacteria can cause a
bad odor, while
diabetes or starvation can cause a sweet, fruity
Specific gravity. This checks the amount of
substances in the urine. It also shows how well the kidneys balance the amount
of water in urine. The higher the specific gravity, the more solid material is
in the urine. When you drink a lot of fluid, your kidneys make urine with a
high amount of water in it, which has a low specific gravity. When you do not
drink fluids, your kidneys make urine with a small amount of water in it, which
has a high specific gravity.
pH is a measure of how acidic or alkaline (basic) the
urine is. A urine pH of 4 is strongly acidic, 7 is neutral (neither acidic nor
alkaline), and 9 is strongly alkaline. Sometimes the pH of urine is affected by
certain treatments. For example, your doctor may instruct you how to keep your
urine either acidic or alkaline to prevent some types of
kidney stones from forming.
Protein. Protein normally isn't found in the
urine. Fever, hard exercise, pregnancy, and some diseases, especially kidney
disease, may cause protein to be in the urine.
Glucose. Glucose is the type of sugar found in
blood. Normally there is very little or no glucose in urine. When the blood
sugar level is very high, as in uncontrolled diabetes, the sugar spills over
into the urine. Glucose can also be found in urine when the kidneys are damaged
Nitrites. Bacteria that cause a
urinary tract infection (UTI) make an enzyme that
changes urinary nitrates to nitrites. Nitrites in urine show a UTI is
Leukocyte esterase (WBC esterase). Leukocyte
esterase shows leukocytes (white blood cells [WBCs]) in the urine.
WBCs in the urine may mean a UTI is present.
Ketones. When fat is broken down for energy, the
body makes substances called ketones (or ketone bodies). These are passed in
the urine. Large amounts of ketones in the urine may mean a very serious
diabetic ketoacidosis, is present. A diet low in
sugars and starches (carbohydrates), starvation, or severe vomiting may also
cause ketones to be in the urine.
Microscopic analysis. In this test, urine is spun
in a special machine (centrifuge) so the solid materials (sediment) settle at
the bottom. The sediment is spread on a slide and looked at under a microscope.
Things that may be seen on the slide include:
- Red or white blood cells. Blood cells aren't found in urine normally. Inflammation,
disease, or injury to the kidneys, ureters, bladder, or urethra can cause blood
in urine. Strenuous exercise, such as running a marathon, can also cause blood
in the urine. White blood cells may be a sign of infection or kidney
- Casts. Some types of kidney disease
can cause plugs of material (called casts) to form in tiny tubes in the
kidneys. The casts then get flushed out in the urine. Casts can be made of red
or white blood cells, waxy or fatty substances, or protein. The type of cast in
the urine can help show what type of kidney disease may be
- Crystals. Healthy people often have
only a few crystals in their urine. A large number of crystals, or certain
types of crystals, may mean kidney stones are present or there is a problem
with how the body is using food (metabolism).
- Bacteria, yeast cells, or parasites. There are no bacteria, yeast cells, or
parasites in urine normally. If these are present, it
can mean you have an infection.
- Squamous cells. The
squamous cells may mean that the sample is not as pure
as it needs to be. These cells do not mean there is a medical problem, but your
doctor may ask that you give another urine sample.