Doctors order basic blood chemistry tests to assess many conditions and learn how
the body’s organs are working.
Often, blood tests check electrolytes, the minerals that help keep the body's fluid
levels in balance and which are necessary to help the muscles, heart, and other organs
work properly. Blood chemistry tests also measure other substances that help show
how well the kidneys
are working and how well the body is absorbing sugars.
Tests for Electrolytes
Typically, tests for electrolytes measure levels of sodium, potassium, chloride,
and bicarbonate in the body.
Sodium plays a major role in regulating the amount of water in
the body. Also, the passage of sodium in and out of cells is necessary for many body
functions, like transmitting electrical signals in the brain and in the muscles. The
sodium levels are measured to detect whether there's the right balance of sodium and
liquid in the blood to carry out those functions.
If a child becomes dehydrated
(from vomiting, diarrhea,
or other causes), the sodium levels can be too high or low, which can cause confusion,
weakness, lethargy, and even seizures.
Potassium is essential to regulating how the heart beats. Potassium
levels that are too high or too low can increase the risk of an abnormal heartbeat
(also called arrhythmias).
Low potassium levels are also associated with muscle weakness and cramps.
Chloride, like sodium, helps maintain a balance of fluids in the
body. Certain medical problems like dehydration, heart disease, kidney
disease, or other illnesses can disrupt the balance of chloride. Testing chloride
in these situations helps the doctor tell whether an acid-base imbalance is happening
in the body.
Bicarbonate prevents the body's tissues from getting too much
or too little acid. The kidney and lungs balance the levels of bicarbonate in the
body. So if bicarbonate levels are too high or low, it might indicate a problem with
Other Substances Measured
Other blood substances measured in the basic blood chemistry test include blood
urea nitrogen and creatinine, which tell how well the kidneys are functioning, and
glucose, which indicates whether there is a normal amount of sugar in the blood.
Blood urea nitrogen (BUN) is a measure of how well the kidneys
are working. Urea is a nitrogen-containing waste product that's created when the body
breaks down protein. If the kidneys are not working properly, the levels of BUN will
build up in the blood. Dehydration, excessive bleeding, and severe infection leading
to shock also can raise BUN levels.
Creatinine levels in the blood that are too high can indicate
that the kidneys aren't working properly. The kidneys filter and excrete creatinine;
if they're not working as they should, creatinine can build up in the bloodstream.
Both dehydration and muscle damage also can raise creatinine levels.
Glucose is the main type of sugar in the blood. It comes from
the foods we eat and is the major source of energy needed to fuel the body's functions.
Glucose levels that are too high or too low can cause problems. The most common cause
of high blood glucose levels is diabetes.
Other medical conditions and some medicines also can cause high blood glucose.