Editing Dehydration (section)

=== Laboratory tests ===
While there is no single gold standard test to diagnose dehydration, evidence can be seen in multiple laboratory tests involving blood and urine. Serum osmolarity above 295 mOsm/kg is typically seen in dehydration due to free water loss.<ref name = "Hooper_2015" /> A urinalysis, which is a test that performs chemical and microscopic analysis of urine, may find darker color or foul odor with severe dehydration.<ref>{{Cite book | vauthors = Hughes G |title=A medication guide to internal medicine tests and procedures |date=2021 |publisher=Elsevier, Inc |isbn=978-0-323-79007-9 |edition=First |location=Philadelphia}}</ref> Urinary sodium also provides information about the type of dehydration. For hyponatremic dehydration, such as from vomiting or diarrhea, urinary sodium will be less than 10&nbsp;mmol/L due to increased sodium retention by the kidneys in an effort to conserve water.<ref>{{Citation |last=Tietze |first=Karen J. |title=Review of Laboratory and Diagnostic Tests |date=2012 |work=Clinical Skills for Pharmacists |pages=86–122 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780323077385100055 |access-date=2024-11-06 |publisher=Elsevier |language=en |doi=10.1016/b978-0-323-07738-5.10005-5 |isbn=978-0-323-07738-5}}</ref> In dehydrated patients with sodium loss due to diuretics or renal dysfunction, urinary sodium may be elevated above 20&nbsp;mmol/L.<ref>{{Cite journal |last1=Yun |first1=Giae |last2=Baek |first2=Seon Ha |last3=Kim |first3=Sejoong |date=2023-05-01 |title=Evaluation and management of hypernatremia in adults: clinical perspectives |journal=The Korean Journal of Internal Medicine |language=en |volume=38 |issue=3 |pages=290–302 |doi=10.3904/kjim.2022.346 |issn=1226-3303 |pmc=10175862 |pmid=36578134}}</ref> Patients may also have elevated serum levels of [[blood urea nitrogen]] (BUN) and [[creatinine]]. Both of these molecules are normally excreted by the kidney, but when the circulating blood volume is low, the kidney can become injured.<ref>{{Cite journal |last1=Mohamed |first1=Mohamed Saied |last2=Martin |first2=Andrew |date=May 2024 |title=Acute kidney injury in critical care |url=https://linkinghub.elsevier.com/retrieve/pii/S1472029924000456 |journal=Anaesthesia & Intensive Care Medicine |language=en |volume=25 |issue=5 |pages=308–315 |doi=10.1016/j.mpaic.2024.03.008}}</ref> This causes decreased kidney function and results in elevated BUN and creatinine in the serum.<ref>{{Citation |last1=Amin |first1=Rasheda |title=Kidney and urinary tract disorders |date=2021 |work=Biochemical and Molecular Basis of Pediatric Disease |pages=167–228 |url=https://linkinghub.elsevier.com/retrieve/pii/B978012817962800010X |access-date=2024-11-06 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-817962-8.00010-x |isbn=978-0-12-817962-8 |last2=Ahn |first2=Sun-Young |last3=Moudgil |first3=Asha}}</ref> {{Further|Portsmouth sign}}