Sodium Change Calculator in Hypertriglyceridemia
Correct pseudohyponatremia caused by high triglycerides with the standard lipid-interference formula.
Enter the measured sodium and triglyceride level to get the corrected sodium. Total lipids and serum protein fields are optional for a more refined estimate.
Sodium Change Calculator in Hypertriglyceridemia
Correct pseudohyponatremia caused by high triglycerides with the standard lipid-interference formula.
About the Sodium Change Calculator in Hypertriglyceridemia
When triglyceride levels are markedly elevated — a condition known as hypertriglyceridemia — laboratory measurements of serum sodium can be artificially lowered. This phenomenon is called pseudohyponatremia. It occurs because the standard flame-photometry and ion-selective electrode methods assume that serum consists mostly of water, but in the presence of large lipid particles the non-aqueous fraction of plasma expands, diluting the measured sodium concentration in the total volume of the sample without changing the actual sodium concentration in the aqueous phase.
The clinical consequence is that clinicians may misinterpret a low measured sodium as true hyponatremia and treat the patient inappropriately with fluid restriction or hypertonic saline. Recognizing and correcting for lipid interference is therefore an essential step in the electrolyte evaluation of any patient with a triglyceride level above 500 mg/dL.
The standard correction formula used in clinical practice is: Corrected Na⁺ (mmol/L) = Measured Na⁺ + (Triglycerides in mg/dL × 0.002). This factor of 0.002 reflects the empirical relationship between lipid volume displacement and sodium underestimation. For every 100 mg/dL rise in triglycerides, approximately 0.2 mmol/L is subtracted from the measured sodium. At extreme triglyceride levels — for example 2,000 mg/dL — the measured sodium can be 4 mmol/L lower than the true value, a clinically meaningful difference.
When total lipid concentration is available (the sum of all lipid fractions including triglycerides, cholesterol, phospholipids, and chylomicrons), the same 0.002 coefficient applied to total lipids gives a more precise estimate of the aqueous sodium concentration. Similarly, when serum protein is abnormally elevated (as in multiple myeloma or macroglobulinemia), an additional correction can be applied because proteins also occupy plasma volume. This calculator incorporates these optional refinements when the data are entered.
It is important to understand that this calculator addresses the analytical interference problem, not an underlying metabolic disturbance in sodium handling. The patient's actual sodium physiology — their tonicity, renal function, and fluid balance — must be assessed independently. A corrected sodium in the normal range (135–145 mmol/L) confirms that the low measured value was an artefact. A corrected sodium that is still low suggests genuine hyponatremia co-existing with hypertriglyceridemia, and further workup is warranted.
This tool is intended as a clinical decision-support aid. All results should be interpreted in conjunction with the patient's clinical picture, history, and other laboratory findings. Medical decisions should not be made on the basis of any single calculator output.
Examples
Worked examples showing how triglyceride-induced sodium interference is corrected in clinical practice.
| Inputs | Corrected Na⁺ | Clinical context |
|---|---|---|
| Na 135 mmol/L, TG 450 mg/dL | 135.9 mmol/L (Δ +0.9) | Mild hypertriglyceridemia — minimal sodium artefact; measured Na is clinically reliable. |
| Na 125 mmol/L, TG 1200 mg/dL | 127.4 mmol/L (Δ +2.4) | Severe hypertriglyceridemia — apparent hyponatremia is partly artefactual; TG lowering is indicated. |
| Na 120 mmol/L, TG 900 mg/dL, Total Lipids 1800 mg/dL | 123.6 mmol/L (Δ +3.6) | Mixed lipid disorder — using total lipids gives a higher, more precise correction than TG alone. |
| Na 115 mmol/L, TG 2500 mg/dL | 120.0 mmol/L (Δ +5.0) | Critical hypertriglyceridemia — measured Na underestimates true value by 5 mmol/L; urgent TG reduction needed. |
How to use this calculator
- Enter the measured serum sodium (Na⁺) in mmol/L as reported by the laboratory.
- Enter the triglyceride level in mg/dL from the same blood sample.
- Optionally enter total lipid concentration and serum protein if available for a more refined correction.
- Click Calculate. The corrected Na⁺ and the delta correction are displayed instantly.
- Compare the corrected sodium to the normal range (135–145 mmol/L) to determine whether hyponatremia is genuine or artefactual.
Frequently Asked Questions
What is pseudohyponatremia?
Pseudohyponatremia is a falsely low measured sodium that occurs when large quantities of lipids or proteins displace water in the plasma sample. The actual sodium concentration in the aqueous phase of blood is normal, but the laboratory result is artificially depressed because the measurement is made on the whole sample volume rather than just the water fraction.
At what triglyceride level does correction become clinically important?
Significant lipid interference is generally seen when triglycerides exceed 500 mg/dL. Below this level the correction is typically less than 1 mmol/L and unlikely to change clinical management. Above 1,000 mg/dL the artefact can exceed 2 mmol/L and should always be accounted for before treating apparent hyponatremia.
Why is 0.002 used as the correction factor?
The factor 0.002 (mmol/L per mg/dL of triglycerides) is derived from empirical studies measuring the relationship between plasma lipid volume fraction and sodium underestimation by indirect potentiometry. It represents approximately 0.2 mmol/L of sodium depression per 100 mg/dL increment in triglycerides. Some authorities use slightly different coefficients, but 0.002 is the most widely cited value in the clinical literature.
Can this calculator be used for cholesterol-induced pseudohyponatremia?
Yes, if you enter the total lipid concentration (which includes cholesterol, triglycerides, and phospholipids) in the optional Total Lipids field, the same coefficient is applied to account for all lipid fractions. Pure hypercholesterolaemia without elevated triglycerides causes less sodium artefact because cholesterol particles are smaller, but the total lipid correction remains valid.
Is a corrected sodium in the normal range always reassuring?
A corrected sodium of 135–145 mmol/L strongly suggests that the low measured value was artefactual. However, this does not exclude co-existing genuine hyponatremia. If the patient has symptoms of hyponatremia (confusion, nausea, seizures) or osmotic findings inconsistent with simple lipid interference, further clinical evaluation is necessary.
Does the formula apply to both flame photometry and ion-selective electrode methods?
The interference is most pronounced with indirect ion-selective electrode (ISE) and flame photometry methods, which dilute the sample before measurement. Direct ISE methods, which measure undiluted serum, are largely unaffected by lipid displacement because they measure sodium activity in the water phase directly. If your laboratory uses direct ISE, the measured value is unlikely to require this correction.