Clinical Tools / Live calculator

Sodium correction calculator

Estimate free water deficit or sodium deficit for small-animal fluid planning. This tool provides arithmetic only. It does not choose a fluid, set a safe correction rate, or interpret the cause of dysnatremia.

Use it for

Turning entered sodium values and a chosen total-body-water factor into a planning estimate.

It calculates

Weight conversion, total body water used, sodium change, and either free water deficit or sodium deficit arithmetic.

It does not decide

Fluid choice, correction pace, monitoring frequency, chronicity, or the underlying cause of dysnatremia.

Input

Enter the sodium estimate

Choose one estimate mode, then enter body weight, current sodium, target sodium, and the total body water factor you want used for the calculation.

Estimate mode Weight unit

Body weight Total body water factor Default assumption: 0.6 × body weight. Adjust for pediatric, geriatric, or body-condition outliers.

Current sodium Target sodium

All sodium values are entered in mEq/L. The total body water factor is an estimate. Chronicity, safe correction rate, and patient condition all affect sodium management. This calculator only checks the entered arithmetic and does not set a safe correction pace.

Result

Sodium estimate

Enter the current and target sodium values to calculate a mode-specific sodium estimate.

Awaiting calculation

Hypernatremia? Use free water deficit estimate. Current sodium must be above target.
Hyponatremia? Use sodium deficit estimate. Target sodium must be above current.
Confirm body weight and the total body water factor before calculating.
Recheck current and target sodium entries before calculating.

Formula

Formula audit trail

Use these steps to verify how the displayed result was calculated.

1. Convert body weight to kg when weight is entered in lb.

2. Total body water = body weight x selected total body water factor.

3. Free water deficit estimate = total body water x ((current sodium / target sodium) - 1).

4. Sodium deficit estimate = total body water x (target sodium - current sodium).

Rounding is for display only. This tool shows planning arithmetic only and does not set a correction rate, fluid choice, or reassessment interval.

Calculation steps will appear for verification.

Safety checks

Review before use

Arithmetic support only. This tool does not decide whether sodium correction is indicated.
The total body water factor is an estimate. Recheck whether it fits the patient before relying on the output.
Chronicity and safe correction rate limits are not modeled by this tool. Review pacing, monitoring, and central pontine myelinolysis risk separately.

Learn

Worked example and practice

Compact learning support for students, using the same arithmetic the live calculator performs.

Worked example

A 10 kg dog has a sodium of 165 mEq/L, target 150 mEq/L, and total body water factor 0.6.

Total body water = 10 kg x 0.6 = 6 L Free water deficit = 6 x ((165 / 150) - 1) = 0.6 L

The planning estimate is 0.6 L of free water deficit, which still needs a separate decision about pacing, fluids, and monitoring.

Try this case

Estimate the answer before revealing it: a 4 kg cat has sodium 120 mEq/L, target 130 mEq/L, and total body water factor 0.6 in sodium-deficit mode.

Reveal worked answer

Total body water = 4 kg x 0.6 = 2.4 L.

Sodium deficit estimate = 2.4 x (130 - 120) = 24 mEq.

That figure is arithmetic only; the actual correction plan and review schedule still need clinical judgment.

Basis

Basis and limits

Calculation basis: entered sodium values, body weight, and the selected total body water factor are converted into either free water deficit or sodium deficit arithmetic.
Scope: this tool supports planning math. It does not choose therapy, correction pace, chronicity assumptions, or monitoring strategy.
Before use: verify the final plan against current protocols, repeat laboratory review, fluid/product details, and the broader patient context.