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
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.
To learn more, see the topic
Sodium (Na) in Urine.
Other electrolytes, such as calcium, chloride, magnesium,
potassium, phosphate, blood urea nitrogen (BUN), and creatinine, may be checked
in a blood sample at the same time as a blood test for sodium.