Evaluation of Sodium Disorders

Last updated: April 6, 2026, 6:50 PM Pacific Time (PDT)

Shared bedside framework for hyponatremia and hypernatremia. Choose whether the main sodium problem is hypo or hyper, then use the adaptive assistant to focus on tonicity, urine studies, water balance, and bedside context without clicking into separate pages.

Interactive diagnostic assistant

Activate the assistant to adapt the page to either hypo- or hypernatremia and re-rank likely mechanisms from entered data.

Sodium pattern Hyponatremia present Hypernatremia present

Sodium (mEq/L, ref about 135-145)

History and bedside clues

Severe neurologic symptoms or rapidly changing sodium ICU, tube-feed, or complex inpatient setting AKI, CKD, or major renal-handling concern

Other labs

Core labs

Serum osmolality (mOsm/kg, ref about 275-295)
Urine osmolality (mOsm/kg)
Urine sodium (mEq/L)
Glucose (mg/dL, ref about 70-180)
Potassium (mEq/L, ref about 3.5-5.0)

Optional labs

TSH (free text)
AM cortisol (free text)
Calcium (mg/dL, ref about 8.5-10.5)

Free-text lab entries are interpreted automatically when they look low, normal, high, dilute, concentrated, suppressed, elevated, or clearly abnormal.

Likely mechanisms

Likely diagnoses from entered data

This is a simplified teaching assistant for bedside sodium reasoning. It supports incomplete data, but severe or rapidly changing dysnatremia still needs immediate clinical judgment and careful correction planning.

Flowchart

Step 1

Name the direction and urgency of the sodium abnormality

Before subtype workup, decide whether this is low sodium, high sodium, or a transitioning mixed inpatient picture, and whether symptoms make the pace urgent.

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Step 2

Use shared anchors

Serum osmolality, urine osmolality, urine sodium, and bedside water-balance clues keep you from over-anchoring too early.

Hyponatremia branch

Tonicity

Confirm hypotonic versus hypertonic or isotonic mimic

Serum osmolality and glucose often redirect the whole workup.

Volume / ADH

Hypovolemic, euvolemic SIADH-pattern, low-solute, or hypervolemic physiology

Urine osmolality plus urine sodium and the bedside exam usually get you close.

Hypernatremia branch

Water problem

Water loss or impaired water access

Most adult hypernatremia is a water-balance problem, not pure sodium overload.

Renal concentration

Osmotic diuresis, central DI, nephrogenic DI, or sodium gain

Urine osmolality and exposure history help separate these quickly.

Teaching pearl: shared sodium frameworks still start with direction, symptoms, and tonicity. The branches diverge after that, but the first bedside questions are surprisingly similar.