Summary
Definition
History and exam
Key diagnostic factors
- past medical history of mental illness or developmental disability
- water-seeking and drinking
Other diagnostic factors
- polyuria
- headache or nausea
- lethargy or confusion
- seizures, delirium, or coma
Risk factors
- mental illness
- anxious, middle-aged women
- developmental disability disorders
- smoking
Diagnostic investigations
1st investigations to order
- plasma osmolality
- urine osmolality
- urine sodium
- serum sodium
- 24-hour urine volume
- urinalysis
- serum BUN
- water restriction test
Investigations to consider
- vasopressin test
- plasma antidiuretic hormone
- CXR
Treatment algorithm
severe hyponatremia (<125 mEq/L) or with neurologic symptoms
hyponatremia (125-130 mEq/L) or with GI symptoms
chronic polydipsia
Contributors
Authors
Shilpa Srinivasan, MD

Associate Professor of Clinical Psychiatry
Department of Neuropsychiatry and Behavioral Science
University of South Carolina School of Medicine
Columbia
SC
Disclosures
SS is a board member of the American Association for Geriatric Psychiatry and serves on the Geriatric Psychiatry Exam Committee for the American Board of Psychiatry and Neurology.
Meera Narasimhan, MD

Chair of the Department of Neuropsychiatry
Department of Neuropsychiatry and Behavioral Science
University of South Carolina School of Medicine
Columbia
SC
Disclosures
MN is a member of an advisory board for Alkermes.
Acknowledgements
Dr Shilpa Srinivasan and Dr Meera Narasimhan would like to gratefully acknowledge Dr Emily Williams and Dr Brian Dundas, previous contributors to this topic. EW and BD declare that they have no competing interests.
Peer reviewers
Pieter Joost van Wattum, MD, MA
Assistant Clinical Professor of Child Psychiatry
Yale School of Medicine
Medical Director of Psychiatry
Clifford W. Beers Guidance Clinic
New Haven
CT
Disclosures
PJvW declares that he has no competing interests.
Branimir Margetić, MD
Neuropsychiatric Hospital "Dr Ivan Barbot
Popovaca
Croatia
Disclosures
BM is an author of a reference cited in this topic.
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