FENa Calculator

FENa is the fraction of filtered sodium that reaches the urine, worked out from a matched pair of blood and urine samples with the formula published by Espinel in JAMA in 1976. Enter the serum and urine sodium, the serum and urine creatinine and the units they came in, and the tool returns the percentage together with the published cut-offs and the conditions known to move them. A second mode does the urea version, FEUrea, which was put forward for patients who have already been given a diuretic and whose FENa can no longer be read. Laboratory values are posted rather than placed in the address bar, so they do not end up in a browser history or a server log. The number is one line of a report, and reading it against a patient is the work of the clinician who ordered the tests.

Calculator Type

Creatinine Units

Both in mg/dL Both in umol/L Serum in umol/L, urine in mmol/L

Four numbers from one matched pair of samples. Both sodium figures must share a unit; mEq/L and mmol/L are the same number.

Serum Sodium (mEq/L or mmol/L) *

Urine Sodium (mEq/L or mmol/L) *

Serum Creatinine (mgdl) *

From the same blood sample as the serum figure above.

Urine Creatinine (mgdl) *

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