Calculate corrected sodium for hyperglycemia using Katz (1.6) and Hillier (2.4) correction factors. Essential for DKA and HHS sodium assessment.
In hyperglycemic states such as diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), the measured serum sodium is artificially lowered by osmotic water shifts. Elevated glucose draws water from intracellular to extracellular space, diluting sodium. The corrected sodium formula estimates the patient's true sodium status — the sodium that would be measured if glucose were normal.
Two correction factors are in common use: the classic Katz factor of 1.6 mEq/L per 100 mg/dL glucose above normal (derived in 1973), and the Hillier factor of 2.4 mEq/L per 100 mg/dL (shown to be more accurate at glucose levels above 400 mg/dL). This calculator presents both values side-by-side, allowing clinicians to see the range and choose the most appropriate correction for their clinical scenario.
Getting the corrected sodium right matters because it determines the IV fluid strategy: if corrected sodium is hyponatremic, half-normal saline should replace normal saline during DKA treatment; if corrected sodium is normal or high, normal saline may cause hypernatremia as glucose normalizes.
Every DKA and HHS patient should have corrected sodium calculated. Without it, clinicians may misinterpret a dilutional hyponatremia as true hyponatremia or miss emerging hypernatremia hidden by the glucose effect. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain. Use this clarification to avoid ambiguous interpretation. Align this note with review checkpoints.
Corrected Na⁺ = Measured Na⁺ + (Correction Factor × (Glucose − 100) / 100). Katz factor = 1.6 mEq/L per 100 mg/dL. Hillier factor = 2.4 mEq/L per 100 mg/dL. Normal reference glucose = 100 mg/dL.
Result: Corrected Na⁺ = 134.4 mEq/L (Katz); 137.6 mEq/L (Hillier)
Glucose excess = 500 − 100 = 400. Katz: 128 + (1.6 × 4) = 134.4. Hillier: 128 + (2.4 × 4) = 137.6. The measured Na of 128 is pseudohyponatremia — corrected sodium is near-normal, meaning the low Na is primarily dilutional from hyperglycemia.
The original correction factor of 1.6 mEq/L per 100 mg/dL was derived by Katz in 1973 based on theoretical osmotic principles and limited clinical data. It became the standard taught in medical schools worldwide. In 1999, Hillier et al. performed a more rigorous study using actual patient data from hyperglycemic episodes and found that a correction factor of 2.4 better fit the observed sodium changes at glucose levels above 400 mg/dL. Neither factor is perfect — the true relationship is non-linear — but both are adequate for clinical decision-making.
In the 2023 ADA consensus statement on DKA management, corrected sodium is used to guide fluid transitions. Initial resuscitation uses 0.9% NaCl for volume expansion regardless of corrected sodium. After the first 1–2 liters, the corrected sodium determines the next fluid: if corrected Na <135, continue 0.9% NaCl; if corrected Na ≥135, switch to 0.45% NaCl at 250–500 mL/h. When glucose drops below 250 mg/dL, dextrose-containing fluids (D5 0.45% NaCl) are added to prevent hypoglycemia while insulin continues to clear ketones.
The correction factor assumes no concurrent sodium disorder. Patients with SIADH and DKA simultaneously, or those on thiazides with DKA, may have both dilutional and true hyponatremia — the corrected sodium will still underestimate the true deficit. Additionally, in HHS with extreme glucose (>1,000), the correction oversimplifies the osmotic relationship. In these cases, serum osmolality measurement and the osmol gap provide additional clinical clarity.
Glucose is an effective osmole that cannot freely cross cell membranes. When blood glucose is high, water moves from intracellular to extracellular space by osmosis, diluting sodium in the process. This is a translocation hyponatremia — total body sodium may be normal or even high.
The Katz factor (1.6) was validated at moderate hyperglycemia (glucose <400 mg/dL). Hillier et al. (1999) showed that at glucose >400, the relationship becomes non-linear and 2.4 is more accurate. For severe DKA/HHS with glucose >400, use 2.4; for moderate hyperglycemia, 1.6 is sufficient.
A high corrected sodium means the patient has lost significant free water (hypernatremic dehydration). As insulin lowers glucose, sodium will rise further. These patients need hypotonic fluid (D5W or half-normal saline) rather than normal saline to prevent worsening hypernatremia.
No. Hyperglycemic hyponatremia is a real redistribution of water (true change in sodium concentration). Lipemic or paraproteinemic pseudohyponatremia is a lab artifact — the sodium is normal by direct ISE measurement. The glucose correction addresses a physiological shift, not a lab error.
If corrected sodium is low or low-normal: use normal saline (0.9% NaCl). If corrected sodium is high-normal or elevated: switch to half-normal saline (0.45% NaCl). The goal is to provide enough sodium to replace losses without causing iatrogenic hypernatremia as glucose drops.
Yes — mannitol, sorbitol, and glycerol are effective osmoles that pull water into the extracellular space, lowering sodium. However, BUN and ethanol freely cross membranes and do NOT cause osmotic water shifts, so they are "ineffective osmoles" that don't affect sodium.