HyponatremiaMANAGEMENT

ENDOCRINE AND METABOLIC PRESENTATIONS · 12 SECTIONS

⚲

524 items

☷ Legend

⚲

Cardiovascular Presentations71▾

Respiratory Presentations52▾

Neurological Presentations83▾

Gastrointestinal Presentations74▾

Genitourinary and Reproductive Presentations48▾

Infectious Disease Presentations148▾

Trauma Presentations89▾

Toxicologic Presentations80▾

Psychiatric Presentations26▾

Musculoskeletal and Rheumatologic Presentations96▾

Dermatology Presentations23▾

Environmental and Exposure Presentations27▾

Hematologic and Oncologic Presentations36▾

Pediatric-Specific Presentations19▾

Endocrine and Metabolic Presentations45▾

Acute Porphyria Adrenal crisis Adrenal Insufficiency (Addisonian Crisis)Dehydration Diabetes Insipidus Diabetic Ketoacidosis (DKA)Euglycemic DKA (SGLT2 inhibitor)Galactosemia GLP-1 receptor agonist complications (retained gastric contents, aspiration risk)Homocystinuria Hypercalcemia Hyperkalemia Hypermagnesemia Hypernatremia Hyperosmolar Hyperglycemic State (HHS)Hypertensive emergency Hypertensive urgency Hypocalcemia Hypoglycemia Hypogonadism (Acute Presentation)Hypokalemia Hypomagnesemia Hyponatremia Hypoparathyroidism (Tetany)Insulin pump failure Maple Syrup Urine Disease (Crisis)Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCAD)Metabolic Acidosis Metabolic Alkalosis Myasthenia gravis crisis Myxedema coma Pellagra Pheochromocytoma (Crisis)Pituitary Apoplexy Pompe Disease (GSD II)Respiratory Acidosis Respiratory Alkalosis Scurvy SIADH Starvation Ketosis Tarui Disease (GSD VII)Thyroid storm Tyrosinemia Vitamin D Deficiency (Severe-Rickets)Von Gierke Disease (GSD I)

ENT and Maxillofacial Presentations27▾

Ophthalmologic Presentations19▾

Obstetric Presentations23▾

Systemic and Miscellaneous Presentations17▾

01Approach to the Critical Patient/attcp39

Immediate priorities

›Hyponatremic encephalopathy recognition

›Seizures — immediate hypertonic saline indication

›Obtundation or coma — immediate hypertonic saline indication

›Respiratory distress — noncardiogenic pulmonary edema from acute water intoxication

›If severe neurological symptoms, initiate 3% hypertonic saline without delay

›100 mL IV bolus over 10 minutes (US guideline)

›Repeat up to 2 to 3 times until symptoms improve

›Airway and circulation

›Airway protection in obtunded patient

›GCS <= 8 warrants consideration of intubation

›Positioning and suction for seizure

›Hemodynamic instability assessment

›Hypotension and tachycardia suggest hypovolemia

›IV access and volume assessment

›Seizure management

›Benzodiazepines for active seizure

›Hypertonic saline is definitive treatment — address sodium simultaneously

Monitoring and targets

›Sodium monitoring protocol

›Serum sodium after each hypertonic saline bolus

›Then every 4 to 6 hours during first 24 hours

›Strict correction rate limits

›Standard risk: no more than 10 to 12 mmol/l per 24 hours

›High ODS risk: no more than 6 to 8 mmol/l per 24 hours

›Escalation triggers

›Sodium rising faster than target rate — stop all sodium-raising therapies

›Administer D5W 3 mL/kg/hr

02History/hx53

Onset and acuity

›Temporal classification

›Acute hyponatremia onset less than 48 hours

›Higher cerebral edema risk at same sodium level

›Aggressive treatment appropriate

›Chronic hyponatremia onset 48 hours or longer or unknown

›Brain has adapted — higher osmotic demyelination syndrome risk with rapid correction

›Conservative correction rate required

›Postoperative setting

›Common trigger for acute hyponatremia

›Hypotonic fluid administration and pain or nausea driving ADH release

Symptoms

›Neurological symptom spectrum

›Mild — headache, nausea, weakness, cognitive slowing

›Moderate — vomiting, confusion, gait instability, falls

›Severe — somnolence, seizures, respiratory distress, coma

›Indicates hyponatremic encephalopathy requiring emergency treatment

›Concurrent symptoms guiding etiology

›Thirst and polyuria — primary polydipsia or diabetes insipidus

›Edema, dyspnea, orthopnea — heart failure

›Jaundice, abdominal distention — cirrhosis

›Weight gain with cold intolerance — hypothyroidism

›Fatigue, hyperpigmentation, weight loss — adrenal insufficiency

Fluid and dietary history

›Excessive fluid intake

›Polydipsia in psychiatric patients

›Endurance exercise and hypotonic fluid replacement

›Ecstasy or MDMA use

03Physical Exam/exam35

Vital signs and general

›Hemodynamic assessment

›Hypotension and tachycardia — suggests hypovolemia

›Hypertension with edema — suggests hypervolemia

›Temperature — fever may suggest underlying pulmonary or CNS cause of SIAD

›Volume status assessment

›Clinical sensitivity 50 to 70% and specificity 30 to 50% for volume depletion

›Hypovolemia signs — dry mucous membranes, poor skin turgor, orthostatic hypotension, flat JVP

›Euvolemia — no edema, no signs of dehydration

›Hypervolemia signs — peripheral edema, ascites, JVD, pulmonary crackles

Neurological examination

›Mental status

›GCS score

›Orientation to person, place, and time

›Concentration and short-term recall

›Focal and safety exam

›Gait assessment — gait instability is common in chronic hyponatremia

›Deep tendon reflexes

›Papilledema — sign of increased intracranial pressure from cerebral edema

Organ-system targeted exam

›Cardiovascular and respiratory

›S3 gallop and elevated JVP — heart failure

›Bilateral crackles — pulmonary edema from heart failure or water intoxication

›Dull percussion base — pleural effusion in cirrhosis or heart failure

›Hepatic stigmata

›Jaundice, spider angiomata, palmar erythema, caput medusae

›Ascites and hepatomegaly

›Thyroid and endocrine

04Differential Diagnosis/ddx55

Tonicity-based classification

›Non-hypotonic hyponatremia — first rule out

›Pseudohyponatremia — isotonic

›ICD-10 E87.1

›Severe hyperproteinemia or extreme hyperlipidemia — lab artifact

›Normal serum osmolality confirms

›Hypertonic hyponatremia

›Hyperglycemia — each 5.6 mmol/l glucose rise decreases sodium by approximately 1.1 mmol/l

›Mannitol or contrast media administration

›Elevated measured serum osmolality confirms

›Hypotonic hyponatremia — serum osmolality less than 275 mOsm/kg

›Subclassified by volume status

›Further workup guided by urine osmolality and urine sodium

Hypovolemic hyponatremia

›Extrarenal losses — urine sodium less than 30 mmol/l

›GI losses — vomiting, diarrhea

›ICD-10 E87.1 with K92.1 or K59.1 context

›Skin losses — burns, excessive sweating

›Third spacing — peritonitis, pancreatitis

›Renal losses — urine sodium greater than 30 mmol/l

›Thiazide diuretics

›Adrenal insufficiency — cortisol and aldosterone deficiency

›Concurrent hyperkalemia is a key clue

›Cerebral salt wasting — differentiate from SIAD by volume status

Euvolemic hyponatremia

›SIAD — syndrome of inappropriate antidiuresis, most common euvolemic cause

›Urine osmolality greater than 100 mOsm/kg with urine sodium greater than 30 mmol/l

›Cancer — small cell lung cancer most common

05Laboratory Tests/lt40

Initial sodium workup

›Essential first-tier labs

›Serum sodium — confirm on BMP or CMP; Na less than 135 mmol/l defines hyponatremia

›Mild 130 to 134 mmol/l

›Moderate 125 to 129 mmol/l

›Severe less than 125 mmol/l

›Serum osmolality — distinguishes hypotonic from isotonic or hypertonic

›Less than 275 mOsm/kg confirms hypotonic hyponatremia

›Normal 285 to 295 mOsm/kg suggests pseudohyponatremia or hypertonic cause

›Urine osmolality — critical for SIAD diagnosis

›Greater than 100 mOsm/kg suggests impaired water excretion — SIAD or volume depletion

›Less than 100 mOsm/kg suggests primary polydipsia or low solute intake

›Urine sodium

›Greater than 30 mmol/l suggests renal losses or SIAD

›Less than 30 mmol/l suggests extrarenal losses or edematous states

Etiology differentiation labs

›Volume status biochemical markers

›BUN and creatinine — elevated in hypovolemia

›Low BUN supports SIAD

›Serum uric acid — low in SIAD, elevated in hypovolemia

›Helps distinguish SIAD from volume-depleted states

›Glucose — rule out hyperglycemic hyponatremia

›Potassium

›Hypokalemia increases osmotic demyelination syndrome risk

›Hyperkalemia suggests Addison disease

›Endocrine screen

›TSH and free T4 — rule out hypothyroidism before diagnosing SIAD

›Morning cortisol and ACTH stimulation — rule out adrenal insufficiency

06Diagnostic Tests/dt69

Scoring Systems

›Severity classification system

›Mild — Na 130 to 134 mmol/l

›Often asymptomatic or nonspecific symptoms

›Associated with increased falls, fractures, and mortality even when asymptomatic

›Moderate — Na 125 to 129 mmol/l

›Nausea, headache, mild cognitive deficits

›Severe — Na less than 125 mmol/l

›Confusion, seizures, coma — medical emergency

›ODS risk stratification

›Standard ODS risk — correction limit 10 to 12 mmol/l per 24 hours

›18 mmol/l per 48 hours

›High ODS risk — correction limit 6 to 8 mmol/l per 24 hours

›Risk factors — alcoholism, liver disease, malnutrition, hypokalemia, Na less than 110 mmol/l

›Meta-analysis of 16 studies (n=11,811) 2025: rapid correction associated with 32 fewer in-hospital deaths per 1,000 without significant ODS increase

›Acuity classification

›Acute less than 48 hours — higher cerebral edema risk, aggressive treatment appropriate

›Chronic 48 hours or longer or unknown — conservative rate, higher ODS risk

MRI

›Brain MRI indications in hyponatremia

›Not required acutely for diagnosis or management

›Clinical and biochemical assessment guides treatment

›Osmotic demyelination syndrome evaluation

›Obtain 2 to 4 weeks after overcorrection episode

›Hyperintense T2 signal in pons — central pontine myelinolysis

›Extrapontine structures — basal ganglia, thalamus, cerebellum

›Intracranial pathology as SIAD cause

›Meningitis or encephalitis with hyponatremia

07Disposition/dispo24

ICU admission

›ICU level care indications

›Severe neurological symptoms requiring hypertonic saline

›Seizures, coma, respiratory distress

›Continuous sodium monitoring required

›Acute hyponatremia with neurological symptoms regardless of sodium level

›Any patient requiring mechanical ventilation

›Osmotic demyelination syndrome with neurological deterioration

Floor and observation admission

›Inpatient admission criteria

›Na less than 125 mmol/l with mild to moderate symptoms

›Na less than 120 mmol/l regardless of symptoms

›High-risk comorbidities — alcoholism, malnutrition, liver disease, active pulmonary disease

›New-onset hyponatremia requiring etiologic workup

›Tolvaptan initiation — must be done in hospital only

Discharge criteria

›Outpatient management criteria

›Mild hyponatremia Na 130 to 134 mmol/l

›Clear reversible cause — recent thiazide initiation

›No significant neurological symptoms

›Chronic stable mild hyponatremia

›Prior documented baseline

›Reliable outpatient follow-up arranged

›Follow-up plan

›Sodium recheck within 24 to 48 hours if medication adjusted or cause recently addressed

›Weekly sodium monitoring for 2 to 4 weeks after starting or stopping causative medication

›Nephrology or endocrinology referral for refractory SIAD or unclear etiology

08Treatment/t60

Emergency treatment for severe symptomatic hyponatremia

›Hypertonic saline protocol

›Indication — seizures, coma, respiratory distress regardless of chronicity

›3% hypertonic saline 100 mL IV bolus over 10 minutes (US guideline)

›European guideline alternative — 150 mL over 20 minutes

›Repeat up to 2 to 3 times until symptoms improve

›Target — raise sodium 4 to 6 mmol/l within 1 to 2 hours

›Sufficient to reverse acute cerebral edema

›Do not aim for normal sodium acutely

›Withhold all hypotonic fluids and offending medications immediately

›Overcorrection rescue

›Stop all sodium-raising therapies immediately

›D5W 3 mL/kg/hr IV

›Lowers sodium back toward target

›Desmopressin 2 to 4 mcg IV

›Halts ongoing free water excretion

›Can be used prophylactically in high ODS risk patients

Hypovolemic hyponatremia treatment

›Volume repletion approach

›Isotonic saline 0.9% as initial resuscitation fluid

›Corrects volume deficit — removes stimulus for ADH secretion

›Monitor sodium closely as correction can overshoot in some patients

›Treat underlying cause

›Stop thiazide diuretics

›Replace GI losses

›Adrenal insufficiency — special case

›Hydrocortisone 100 mg IV immediately

›Then 50 mg IV every 6 to 8 hours

09Special Populations/sp50

Pregnancy

›Physiological considerations

›Normal serum sodium lower in pregnancy — 133 to 136 mmol/l due to ADH reset

›Interpret sodium relative to gestational norms

›Oxytocin has intrinsic antidiuretic activity

›Risk of hyponatremia with oxytocin infusion plus hypotonic fluids in labor

›Use isotonic fluids during labor

›Acute symptomatic treatment

›Hypertonic saline indicated for severe symptoms — same principles apply

›Fetal monitoring when viable gestation during treatment

›Obstetric consultation for preterm or term pregnancy

›Beta-lactams and most supportive agents safe

›Tolvaptan — not established as safe in pregnancy; avoid

›Etiology in pregnancy

›Hyperemesis gravidarum — hypovolemic hyponatremia

›SIAD from severe nausea and pain driving ADH

›Postpartum pituitary infarction — Sheehan syndrome causing adrenal insufficiency

Geriatric

›Age-related susceptibility

›Impaired urinary dilution and aquaresis with age

›Reduced ability to excrete free water load

›Polypharmacy — thiazides, SSRIs most common culprits in elderly

›Low-solute diet — tea-and-toast pattern common

›Reduced thirst sensation — dehydration alternating with overdrinking

›Clinical presentation differences

›Falls and gait instability as presenting complaint — sodium often not measured initially

›Cognitive decline misattributed to dementia

›Chronic mild hyponatremia linked to osteoporosis and hip fracture

10Background/b51

Epidemiology

›Frequency and burden

›Most common electrolyte disorder — affects approximately 5% of adults overall

›Up to 35% of hospitalized patients have some degree of hyponatremia

›Sodium 130 to 134 mmol/l most prevalent range in hospitalized patients

›Mortality association — even mild hyponatremia associated with increased mortality in hospitalized patients

›Contributes to falls, fractures, cognitive decline, osteoporosis

›Population-specific rates

›Thiazide-induced — up to 30% of patients on thiazides affected

›SSRI-induced SIAD — up to 32% of patients

›Duloxetine and escitalopram carry highest risk based on 2025 registry data

›ICU prevalence higher — over 40% in some cohorts

›Osmotic demyelination syndrome — rare but devastating complication of overcorrection

Pathophysiology

›Mechanisms of water retention

›ADH excess — central to most hyponatremia syndromes

›Appropriate ADH release — hypovolemia, pain, nausea, stress

›Inappropriate ADH release — SIAD

›Reset osmostat — lower sodium set point for ADH secretion

›Pregnancy, psychiatric illness, malignancy

›Primary polydipsia — overwhelming renal dilution capacity

›Urine maximally diluted, urine osmolality less than 100 mOsm/kg

›Cerebral edema mechanism

›Hypo-osmolality drives water into brain cells

›Brain volume increases — symptoms from raised intracranial pressure

›Brain adaptation — extrusion of electrolytes and organic osmoles over 48 hours

›Chronic hyponatremia — brain has adapted, less edema at same sodium

›Rapid correction — reversal of adaptation causes osmotic stress — demyelination

11Patient Discharge Instructions/pdi26

copy discharge instructions

›Low sodium level home care

›Take all prescribed medications exactly as directed

›Drink fluids only as much as your doctor recommended — do not over-restrict or over-drink

›If placed on fluid restriction, measure your daily fluid intake

›Eat normal meals with adequate salt and protein unless directed otherwise

›Medications to be aware of

›If a water pill (thiazide diuretic) was stopped, do not restart without doctor approval

›If an antidepressant was identified as a cause, discuss alternatives with your doctor before stopping any medication on your own

›Warning signs — return to emergency immediately for

›Confusion or difficulty thinking

›Severe headache

›Seizure

›Difficulty walking or sudden falls

›Extreme drowsiness or difficulty waking

›Persistent vomiting

›Difficulty breathing

›Follow up instructions

›Blood test to recheck your sodium level within 24 to 48 hours as directed

›Return to your family doctor or specialist within 1 week

›Bring a list of all your medications to your next appointment

›If your sodium was caused by a medication, weekly sodium checks may be needed for 1 month

›Lifestyle guidance

›Avoid excessive water or fluid intake — more is not better

›If you exercise strenuously, do not drink large amounts of plain water — sports drinks with electrolytes are safer for prolonged exercise

›Avoid ecstasy or MDMA — can cause life-threatening hyponatremia

›Alcohol use disorder increases your risk of serious complications — seek help if needed

12References/r22

Guidelines and key sources

›Key clinical references

›Adrogué HJ, Tucker BM, Madias NE — Diagnosis and Management of Hyponatremia: A Review — JAMA 2022

›Miller NE, Rushlow D, Stacey SK — Diagnosis and Management of Sodium Disorders — American Family Physician 2023

›Adrogué HJ, Madias NE — The Syndrome of Inappropriate Antidiuresis — NEJM 2023

›Spasovski G — Hyponatraemia-Treatment Standard 2024 — Nephrology Dialysis Transplantation 2024

›Beck J — Treatment of Chronic Hyponatremia and Controversy About Osmotic Demyelination Syndrome — Best Practice Research Clinical Endocrinology Metabolism 2025

›Drug-induced hyponatremia references

›Mannheimer B et al — Drug-Induced Hyponatremia in Clinical Care — European Journal of Internal Medicine 2025

›Mo H et al — Hyponatremia Associated With Common Antidepressants in the All of Us Research Program — Clinical Pharmacology and Therapeutics 2025

›Seifert J et al — Psychotropic Drug-Induced Hyponatremia — Journal of Neural Transmission 2021

›Pinkhasov A et al — Management of SIADH-related Hyponatremia Due to Psychotropic Medications — Journal of Psychosomatic Research 2021

›Meta-analysis and outcomes

›Ayus JC, Moritz ML, Fuentes NA et al — Correction Rates and Clinical Outcomes in Hospitalized Adults With Severe Hyponatremia — JAMA Internal Medicine 2025

›Hoorn EJ, Zietse R — Diagnosis and Treatment of Hyponatremia: Compilation of the Guidelines — Journal of American Society of Nephrology 2017

›Achinger SG, Ayus JC — Treatment of Hyponatremic Encephalopathy in the Critically Ill — Critical Care Medicine 2017

›Diagnostic algorithm references

›Lin R, Grossmann M, Warren AM — Diagnostic Algorithm of Hyponatremia — Best Practice Research Clinical Endocrinology Metabolism 2025

›Prince R, Chifu I, Arshad MF — Treatment of Acute Symptomatic Hyponatraemia in the Hospital Setting — Best Practice Research Clinical Endocrinology Metabolism 2025

›Coding standards

›ICD-10 E87.1 — hyponatremia

›ICD-10 E22.2 — syndrome of inappropriate secretion of antidiuretic hormone

›SNOMED CT — hyponatremia disorder concept

Learn More: Hyponatremia→

Comprehensive Clinical Review

Structured, evidence-informed, long-form analysis for deeper understanding.

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed August 18, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.