A test for sodium in the urine is a 24-hour test or a one-time (spot) test that checks how much sodium is in the urine Sodium in one-time urine sample Normal: Greater than 20 milliequivalents per liter (mEq/L) What To Think About ONE may look at urine sodium and blood sodium levels to see whether conditions or medicines may be causing fluid or electrolyte imbalances. Urine sodium levels are often high when blood levels are low or low when blood levels are high. Urine sodium levels are affected by medicines and hormones. * 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. References Pagana KD, Pagana TJ (2006). Mosbyâ€™s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.