Estimation of 24-hour sodium excretion from spot urine samples Academic Article uri icon


MeSH Major

  • Circadian Rhythm
  • Hypertension
  • Sodium


  • Despite the effects of sodium intake on blood pressure and on response to antihypertensive medication, sodium intake is rarely monitored in clinical practice. The current method, the 24-hour urine collection for sodium excretion, is cumbersome, often incorrectly performed, and not commonly ordered. Further, its results have limited meaning because of the substantial day-to-day variation in sodium intake. A spot urine test to enable convenient, inexpensive, and serial monitoring of sodium excretion would be desirable. In this study, the accuracy of predicting 24-hour sodium excretion from a spot urine sample was assessed. The urine sodium/creatinine ratio was determined from the following urine samples: an "AM sample," submitted at the beginning of the 24-hour urine collection; a "PM sample" collected in the later afternoon/early evening before dinner, at roughly the midpoint of the collection; and a "random sample," collected after its completion. The ratio was then corrected for 24-hour creatinine excretion. The strongest correlation between predicted and actual 24-hour sodium excretion was observed with the PM sample collected near the midpoint (r=0.86, P<.001). This sample also identified persons with sodium excretion <100 mEq/d with a sensitivity of 100% and specificity of 82%. The sodium/creatinine ratio from a spot urine sample collected in the late afternoon/early evening at roughly the midpoint of the 24-hour collection, and adjusted for 24-hour creatinine excretion, strongly correlated with 24-hour sodium excretion. Additional studies are merited to further evaluate the role of the spot urine sample in assessing sodium intake.

publication date

  • March 2010



  • Academic Article



  • eng

Digital Object Identifier (DOI)

  • 10.1111/j.1751-7176.2009.00241.x

PubMed ID

  • 20433530

Additional Document Info

start page

  • 174

end page

  • 80


  • 12


  • 3