A
sodium test checks how much sodium (an
electrolyte and a mineral) is in the blood. Sodium is
both an electrolyte and mineral. It helps keep the water (the amount of fluid
inside and outside the body's cells) and electrolyte balance of the body.
Sodium is also important in how nerves and muscles work.
Most of
the sodium in the body (about 85%) is found in blood and
lymph fluid. Sodium levels in the body are partly
controlled by a
hormone called aldosterone, which is made by the
adrenal glands. Aldosterone levels tell the kidneys
when to hold sodium in the body instead of passing it in the urine. (See a
picture of the
adrenal glands or the
kidneys.) Small amounts of sodium are also lost
through the skin when you sweat.
Most foods have sodium naturally
in them or as an ingredient in cooking. Sodium is found in table salt as sodium
chloride or in baking soda as sodium bicarbonate. Many medicines and other
products also have sodium in them, including laxatives, aspirin, mouthwash, and
toothpaste.
Too much sodium in the diet may raise blood pressure
in some people. For those who have high blood pressure, eating foods with a lot
of sodium makes their chance of heart disease,
stroke, and kidney damage higher.
Heart failure gets worse when too much sodium is
eaten. It increases the amount of water the body holds in and this causes
swelling of the legs and hands. Some people have problems when they eat more
than 4,000 milligrams (mg) of sodium per day.
Low sodium levels
are uncommon and most often occur as a side effect of taking medicines that
make you urinate more, such as
diuretics. Severe diarrhea or vomiting or heavy
sweating may also cause low sodium levels.
Other electrolytes,
such as potassium, calcium, chloride, magnesium, and phosphate, may be checked
in a blood sample at the same time as a blood test for sodium.
You do not need to do anything before
having this test.
Talk to your health professional about any
concerns you have regarding the need for the test, its risks, how it will be
done, or what the results will mean. To help you understand the importance of
this test, fill out the
medical test information form(What is a PDF document?).
Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
Clean the needle site with
alcohol.
Put the needle into the vein. More than one needle stick
may be needed.
Attach a tube to the needle to fill it with
blood.
Remove the band from your arm when enough blood is
collected.
Put a gauze pad or cotton ball over the needle site as
the needle is removed.
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
pinch.
There is very little chance of a problem from
having blood sample taken from a vein.
You may get a small bruise at the site. You can
lower the chance of bruising by keeping pressure on the site for several
minutes.
In rare cases, the vein may become swollen after the blood
sample is taken. This problem is called phlebitis. A warm compress can be used
several times a day to treat this.
Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.
A sodium test checks how much sodium (an
electrolyte and a mineral) is in the blood. Normal
values may vary from lab to lab. Results are ready in 1 day.
Many conditions can affect sodium levels. Your doctor will
talk with you about any abnormal results that may be related to your symptoms
and medical history.
High values
High sodium levels (hypernatremia) can be
caused by a high-sodium diet or by not drinking enough water and being
dehydrated. Dehydration may also be caused by severe
vomiting or diarrhea,
Cushing's syndrome, kidney disease or injury,
diabetic ketoacidosis, or a condition called diabetes
insipidus that makes it hard to balance the water level in the
body.
High sodium levels can also be caused by high levels of the
hormone aldosterone (hyperaldosteronism).
Low values
Low sodium levels (hyponatremia) can be
caused by a lot of sweating, burns, severe vomiting or diarrhea, drinking too
much water (psychogenic polydipsia), or poor nutrition.
When the sodium level changes quickly, you are
likely to have more symptoms than when the level changes slowly. Symptoms of an
abnormal sodium level include confusion, lack of energy (lethargy), or
seizures.
To see whether the body is passing too little or too much
sodium in the urine, a value called the fractional excretion of sodium (FENa)
can be found by looking at the amounts of sodium and creatinine in blood and
urine. In a person with kidney failure, a low FENa may mean less blood flow to
the kidneys is causing the kidney failure. A urine test for sodium may be done.
For more information, see the medical test
Sodium (Na) in Urine.
This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.
