JPSIM Journal of Pakistan Society of Internal Medicine J Pak Soc Intern Med 2709-8729 2710-0804 Pakistan Society of Internal Medicine 10.70302/jpsim.v6i4.2557 jpsim.v6i4.2557 Review Article Sodium Balance and Imbalance: A Review Linking Physiology with Pathophysiology Wang Samuel Sherng Young Tang Haoming Ng Wang Chin Eileen Li Yi Xin Ho Yu Theng Rachel Luo Xiao Ran Javaid Muhammad M mmjavaid@doctors.org.uk * Tan Tock Seng Hospital, Singapore Duke-NUS Medical School, Singapore Monash Rural Health Mildura, Monash University, Victoria, Australia, South West Healthcare, Warrnambool, Victoria, Australia. Deakin School of Medicine, Deakin University, Warrnambool, Victoria, Australia *Correspondence: Muhammad M Javaid (mmjavaid@doctors.org.uk) 21 11 2025 2025 6 4 308 314 26 05 2025 22 08 2025 11 10 2025 Copyright © 2025 The Author(s) 2025 The Author(s) https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Sodium (Na+), one of the major extracellular cations in the body, exerts a significant role in regulating body fluid compartments and generating action potentials. It represents one of the most important and readily available biomarkers of fluid status. Disturbances of Na+ homeostasis are frequently observed in outpatient and inpatient settings and can be challenging to clinicians attempting to decipher the underlying aetiologies. Various disorders involving the renal, endocrine, and central nervous systems can lead to dysnatremias and imbalance in volume status. Understanding the diverse physiological mechanisms involved in normal Na+ regulation and the expected pathological outcomes when the normal processes are disrupted is crucial in assisting clinicians with coming up with reasonable differential diagnoses and targeted management plans for Na+ disorders. This review summarises the pathophysiology of Na+ disorders by linking it closely with normal Na+ homeostasis.

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