Sodium Correction for Hypertriglyceridemia (pseudohyponatremia)

Understanding the sodium correction for hypertriglyceridemia — concept and principle

This calculator estimates how much very high triglycerides lower a reported sodium value through pseudohyponatraemia, a measurement artefact. It gives the corrected sodium by a quick rule and the plasma water fraction by the Waugh equation. Clinicians use it before treating a low sodium in a patient with milky (lipaemic) blood.

Fat takes the place of water: with the default inputs the result is 133 mmol/L (128 + 5 corrected sodium).

How it is calculated

Sodium change (mmol/L) = 0.002 × triglycerides (mg/dL)

Corrected sodium = measured sodium + change

Plasma water (%) = 99.1 − 0.73 × total protein (g/dL) − 1.03 × lipids (g/dL)

Sodium per litre of plasma water = measured sodium ÷ (plasma water ÷ 100)

Triglycerides stand in for total lipids; 1,000 mg/dL = 1 g/dL.

The principle

Sodium is dissolved only in the water part of plasma. Fats and proteins take up volume but hold no sodium. Many laboratory analysers dilute the sample before measuring (indirect ion-selective electrode) and assume a normal water fraction of about 93%. When large amounts of fat displace water, the same diluted volume contains less water, so the analyser reports a falsely low sodium, even though the concentration in the water the cells actually see is normal. A direct electrode, as on most blood-gas analysers, measures the water phase and is not affected.

Worked example

Default inputs: measured sodium 128 mmol/L, triglycerides 2,500 mg/dL, total protein 7.0 g/dL.

Change = 0.002 × 2,500 = 5 mmol/L.
Corrected sodium = 128 + 5 = 133 mmol/L.
Plasma water = 99.1 − 0.73 × 7.0 − 1.03 × 2.5 = 99.1 − 5.11 − 2.575 = 91.4%.
Sodium per litre of water = 128 ÷ 0.9142 = 140 mmol/L.

Each point is the calculator re-run with only “Triglycerides (mg/dL)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Triglycerides (mg/dL)	Sodium after lipid correction (mmol/L)
625	129.3
1,250	130.5
1,875	131.8
2,500	133
3,125	134.3
3,750	135.5
5,000	138

How to read the result

If the corrected value is normal, the low reading is likely an artefact and treating it could cause harm. Note that on the plasma-water scale normal plasma gives roughly 150 mmol/L, so 140 is not directly comparable with usual reference ranges. The best step is to ask the lab for a direct ISE measurement.

Common mistakes

Entering triglycerides in mmol/L. This calculator expects mg/dL.
Treating hyponatraemia without checking for lipaemia or very high protein.
Applying the correction to a direct-ISE (blood-gas) sodium.

Keep in mind: This is a decision aid for clinicians, not a diagnosis. Very high triglycerides can themselves cause pancreatitis and need medical care.

Frequently asked questions

What is pseudohyponatraemia?

A falsely low sodium result caused by excess fat or protein in the sample, not a true low sodium in the body.

Does high blood sugar cause the same thing?

No. High glucose draws water out of cells and truly dilutes sodium; that needs a different correction.

How do I convert triglycerides from mmol/L?

Multiply mmol/L by about 88.5 to get mg/dL.

Sources: MSD Manual Professional calculator, "Sodium Change in Hypertriglyceridemia" · Aziz F et al., "Pseudohyponatremia: Mechanism, Diagnosis, Clinical Associations and Management", J Clin Med 2023;12(12):4076 · Waugh WH, Metabolism 1969;18:706–712

Checked 9 Nov 2026. Quick rule: MSD Manual Professional Edition medical calculator “Sodium Change in Hypertriglyceridemia” (Na change = triglycerides × 0.002); Waugh WH, Metabolism 1969;18:706–712, equation as given in Aziz F et al., “Pseudohyponatremia: Mechanism, Diagnosis, Clinical Associations and Management”, J Clin Med 2023;12(12):4076 (Formula 1); 93% normal plasma water: Acute Care Testing (Radiometer), “Spurious sodium results (1): pseudohyponatremia”.

Your numbers