Sodium Correction Calculator (Hyperglycemia) | Katz Formula

Why Hyperglycemia Lowers Sodium

Glucose is an "Osmole," meaning it exerts osmotic pressure. When blood sugar is extremely high (Hyperglycemia), it draws water out of the cells and into the blood vessels to try and balance the concentration.

This influx of water significantly dilutes the concentration of sodium in the blood. The total amount of sodium in the body hasn't necessarily changed, but the lab test reads "Low Sodium" (Hyponatremia) because of the extra water. This is called Translocational Hyponatremia.

Managing DKA & HHS

Accurate sodium correction is a critical step in treating Diabetic Ketoacidosis (DKA) and Hyperosmolar Hyperglycemic State (HHS).

DKA (Diabetic Ketoacidosis)

Patients are severely dehydrated. Using the corrected sodium guides fluid choice:

• Corrected Na Low → Use 0.9% Normal Saline.
• Corrected Na Normal/High → Use 0.45% Saline.

HHS (Hyperosmolar State)

Glucose levels often exceed 600 mg/dL, causing a massive artificial drop in sodium. Failing to correct for this can lead to dangerous over-treatment with salt.

Frequently Asked Questions

What happens if I treat the uncorrected sodium?

Treating a falsely low sodium level with hypertonic saline or aggressive salt replacement can lead to Hypernatremia (dangerously high sodium). This rapid shift causes cells to shrink, potentially triggering Osmotic Demyelination Syndrome (ODS), a catastrophic brain injury. Always correct for glucose before treating hyponatremia in diabetics.

Is the Katz formula the only one?

The Katz Formula (1.6) is the most widely used standard. However, the Hillier Formula (2.4) suggests that for extremely high glucose levels (>400 mg/dL), the shift is even stronger. This calculator uses the Katz method (1.6) as it is the conservative clinical standard recommended by UpToDate and most hospital protocols.

Does this apply to Hypoglycemia (Low Sugar)?

No. This correction only works one way. Low blood sugar does not concentrate sodium significantly enough to require a formula. If glucose is normal (< 100 mg/dL), the lab result for sodium is accurate and requires no adjustment.

Why is sodium important in DKA treatment?

In Diabetic Ketoacidosis, the type of IV fluid given depends on the sodium. If the corrected sodium is low, doctors use 0.9% Normal Saline. If the corrected sodium is normal or high, they switch to 0.45% (Half-Normal) Saline to prevent sodium overload while rehydrating the patient.

What is Pseudohyponatremia?

Pseudohyponatremia is a lab artifact where sodium appears low but the body's water balance is actually normal. It is usually caused by high lipids (triglycerides) or high protein (paraproteinemia). Hyperglycemia causes "Translocational Hyponatremia," which is slightly different (water actually moves), but the treatment principle—fixing the underlying cause first—is similar.

References

Katz MA. (1973). New England Journal of Medicine: Hyperglycemia-induced hyponatremia.
Hillier TA, et al. (1999). American Journal of Medicine: Evaluating the correction factor.
American Diabetes Association (ADA). Hyperglycemic Crises Guidelines.
Medscape. Hyponatremia Workup & Correction.

Tools & Data Verified by the EverydayCalculators Medical Research Team.

Last updated: January 2026.

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