How to calculate corrected sodium in DKA?

Corrected Na = Measured Na + 1.6 × (Glucose mg/dL - 100) / 100. Example: measured Na 128 mEq/L, glucose 500 mg/dL. Corrected Na = 128 + 1.6 × 4 = 128 + 6.4 = 134.4 mEq/L (near normal). Some use 2.4 for glucose above 400 mg/dL (Hillier 1999). The corrected value predicts sodium once glucose normalizes with insulin treatment.

How often should sodium be monitored during DKA treatment?

Measure sodium (and glucose) every 2 hours during the initial DKA treatment phase. As glucose falls with insulin therapy, the measured sodium should rise proportionally. Calculate corrected sodium at each measurement to track true sodium trends. ADA Clinical Practice Standards (2024) recommend monitoring electrolytes every 2-4 hours during DKA treatment. More frequent monitoring (every 1-2 hours) is appropriate when glucose is changing rapidly or sodium trends are unexpected.

What is the 1.6 vs 2.4 correction factor debate?

The original Katz (1973) correction factor of 1.6 mEq/L per 100 mg/dL glucose was derived from theoretical plasma water calculations. Hillier et al. (Ann Intern Med 1999) measured actual sodium changes during hyperglycemic clamp studies and found the true correction factor was 2.4 mEq/L per 100 mg/dL — 50% higher than Katz's estimate. The difference is most clinically significant at glucose above 400 mg/dL. Many current guidelines recommend 2.4 for practical use.

Can glucose-corrected sodium predict cerebral edema risk in DKA?

Sodium trends during DKA treatment are associated with cerebral edema risk. Failure of measured sodium to rise as glucose falls (corrected sodium declining) suggests excessive free water administration and is a risk factor for cerebral edema. The Pediatric Emergency Care Applied Research Network (PECARN) identified failing sodium to rise during DKA treatment as a risk factor for cerebral edema in children. Target: measured sodium should increase by ~1-2 mEq/L for each 100 mg/dL glucose decrease.

What is effective serum osmolality and how does it relate to corrected sodium?

Effective serum osmolality (tonicity) = 2 × Na + Glucose/18. This excludes BUN because urea freely crosses cell membranes and does not contribute to osmotic water shifts. Normal effective osmolality is 275-290 mOsm/kg. In HHS, effective osmolality above 320-340 mOsm/kg causes neurological symptoms. Tracking effective osmolality alongside corrected sodium provides the most complete picture of hyperglycemic sodium-osmolality disorders.

How is sodium affected during insulin therapy for DKA?

During DKA treatment: as insulin reduces glucose, osmotic water shifts reverse — water moves from extracellular back into cells. This should cause measured sodium to rise. Expected rate: sodium rises 1.5-2 mEq/L per 100 mg/dL glucose decrease (mirroring the correction formula in reverse). If sodium rises faster than expected, the patient needs more free water. If sodium is not rising despite falling glucose, suspect excessive hypotonic fluid or SIADH.

What fluids are appropriate when corrected sodium is high in DKA?

When corrected sodium is above 145 mEq/L in DKA or HHS (true underlying hypernatremia): initial volume resuscitation still uses 0.9% NaCl (isotonic). Once hemodynamically stable, switch to 0.45% NaCl with appropriate potassium supplementation to provide free water and treat hypernatremia. Avoid 5% dextrose until glucose is below 200 mg/dL. Target corrected sodium correction rate: no faster than 0.5-1 mEq/L/hour to prevent cerebral edema from osmolality changes.

Online Medical Tools — Corrected Sodium

Printed on 8/14/2026

For informational purposes only. This is not medical advice.

Clinical

Corrected Sodium

Hyperglycemia causes osmotic water shift from intracellular to extracellular space, diluting serum sodium. The Katz correction (Na + 1.6 × (glucose − 100)/100) estimates the true sodium level if glucose were normal. This is essential in DKA and HHS management. For full sodium workup, calculate Serum Osmolality Calculator to check osmolar gap. For DKA, also calculate Anion Gap to quantify metabolic acidosis. Check ABG interpretation for acid-base context with ABG Interpreter. Monitor renal function during DKA/HHS treatment with eGFR Calculator.

Formula: Corrected Na = Measured Na + 1.6 × (Glucose − 100) / 100

Measured Serum Sodium

mEq/L

Serum Glucose

mg/dL

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How It Works

Understand why hyperglycemia lowers serum sodium

Glucose is an osmotically active solute that cannot freely cross most cell membranes. Elevated blood glucose creates an osmotic gradient drawing water from the intracellular space into the extracellular space (bloodstream). This water dilutes the sodium concentration, producing a factitious hyponatremia — sometimes called pseudohyponatremia or dilutional hyponatremia from hyperglycemia. The true total body sodium content is unchanged; it is simply diluted by the glucose-driven water shift.

Apply the Katz correction formula

Corrected Na = Measured Na + 1.6 × (Glucose - 100) / 100. For each 100 mg/dL elevation in glucose above 100 mg/dL, add 1.6 mEq/L to the measured sodium. Example: measured Na 128 mEq/L, glucose 500 mg/dL — Corrected Na = 128 + 1.6 × (500 - 100)/100 = 128 + 6.4 = 134.4 mEq/L. Note: some authorities (Hillier et al. 1999) recommend using 2.4 instead of 1.6 for glucose above 400 mg/dL, as 1.6 underestimates correction at extreme hyperglycemia.

Interpret corrected sodium to guide DKA and HHS management

Corrected Na 135-145 mEq/L: apparent hyponatremia is entirely from glucose dilution; treat with insulin and isotonic fluids. As glucose falls, measured sodium will rise toward corrected value. Corrected Na above 145 mEq/L: patient has underlying true hypernatremia masked by dilution — indicates significant free water deficit (classic in HHS). Corrected Na below 135 mEq/L: true hyponatremia coexists with hyperglycemia — investigate other causes (SIADH, adrenal insufficiency, excessive hypotonic fluids).

Who Uses the Corrected Sodium

Diabetic Ketoacidosis (DKA) Sodium Monitoring

Emergency physicians, endocrinologists, intensivists

A patient with DKA has glucose 550 mg/dL and measured sodium 130 mEq/L. Corrected sodium = 130 + 1.6 × (550 - 100)/100 = 137.2 mEq/L (normal). Treatment: isotonic saline initially for volume, then insulin. As glucose corrects, measured sodium should rise toward 137 mEq/L. Failure of measured sodium to rise during treatment suggests excessive free water administration or concurrent SIADH. Track corrected sodium at each glucose check to guide fluid management.

Hyperglycemic Hyperosmolar State (HHS) Severity Assessment

Emergency physicians, endocrinologists

HHS typically shows higher corrected sodium than DKA, reflecting more profound dehydration and less acidosis. Corrected sodium in HHS is often 145-155 mEq/L or higher, confirming massive free water deficit. The degree of hypernatremia predicts fluid deficit magnitude (each 1 mEq/L above 140 represents approximately 1-2 L free water deficit in a 70 kg patient). HHS osmolality is often above 320-340 mOsm/kg — calculate with the Serum Osmolality Calculator.

Predicting Sodium Rise During DKA Treatment

Endocrinologists, ICU nurses, hospitalists

As insulin lowers glucose during DKA treatment, the osmotic water shift reverses — water moves back into cells, and measured sodium rises. The corrected sodium predicts the endpoint sodium. If corrected sodium is 140 mEq/L, the measured sodium should approach 140 as glucose normalizes. Monitor sodium every 2-4 hours. Rapid sodium rise (above 2 mEq/L/hour) suggests the patient is receiving too little free water; stable or falling corrected sodium suggests adequate or excessive hydration.

Detecting True Hypernatremia Masked by Hyperglycemia

ICU physicians, endocrinologists

A patient with uncontrolled diabetes and altered mental status has measured Na 142 mEq/L (appears normal) and glucose 900 mg/dL. Corrected sodium = 142 + 1.6 × (900-100)/100 = 142 + 12.8 = 154.8 mEq/L (markedly elevated). This patient has severe underlying hypernatremia masked by glucose dilution. As insulin is given, the measured sodium will spike dramatically unless adequate free water is co-administered. This calculation prevents potentially dangerous hypernatremia during DKA/HHS treatment.

ICU and Perioperative Sodium Management

Intensivists, anesthesiologists

In any critically ill patient receiving insulin infusions for hyperglycemia, corrected sodium guides appropriate fluid selection. Isotonic saline raises sodium and treats hyperglycemia-driven dilution. Half-normal saline (0.45% NaCl) provides free water and is appropriate when corrected sodium is elevated. Tracking corrected sodium prevents both under-treatment of true hypernatremia and over-treatment causing hyponatremia during glucose correction.

Pro Tips

Use 2.4 instead of 1.6 for glucose above 400 mg/dL

The traditional Katz 1.6 correction factor was derived theoretically and validated in mild-to-moderate hyperglycemia. Hillier et al. (Ann Intern Med 1999) demonstrated that 1.6 underestimates correction by approximately 40% at glucose levels above 400 mg/dL. The empirically derived correction factor of 2.4 mEq/L per 100 mg/dL glucose elevation is more accurate in severe hyperglycemia (glucose above 400 mg/dL, common in DKA and HHS).

Track corrected sodium during DKA treatment, not just measured sodium

During DKA treatment with insulin, glucose falls and measured sodium rises — this is expected and not concerning if corrected sodium remains stable. An appropriate response is measured sodium rising 1-2 mEq/L for every 100 mg/dL glucose decrease. If measured sodium rises faster (corrected sodium increases), the patient is relatively dehydrated — increase free water. If corrected sodium is falling, the patient may be receiving too many hypotonic fluids.

HHS corrected sodium predicts free water deficit

In HHS, corrected sodium is typically 145-155 mEq/L or higher, reflecting massive free water deficit. Approximate free water deficit = 0.6 × weight(kg) × (corrected Na/140 - 1). Example: 70 kg patient with corrected Na 155 = 0.6 × 70 × (155/140 - 1) = 42 × 0.107 = 4.5 liters free water deficit. Replace deficit slowly over 24-48 hours to avoid cerebral edema from rapid osmolality changes.

Distinguish glucose-driven dilutional hyponatremia from SIADH

Corrected sodium tools out glucose contribution: if corrected sodium is normal (135-145), the hyponatremia is entirely explained by hyperglycemia. If corrected sodium remains low (below 135) despite correction, SIADH, adrenal insufficiency, hypothyroidism, or other causes must be investigated. Do not assume all hyponatremia in a hyperglycemic patient is from glucose — the corrected sodium reveals if a second disorder is present.

Calculate effective serum osmolality to predict symptoms

Effective serum osmolality = 2 × Na + Glucose/18 (omit BUN as urea is not osmotically active at membranes). Normal is 275-290 mOsm/kg. Effective osmolality above 320-340 mOsm/kg in HHS drives neurological symptoms (stupor, coma, seizures). Tracking effective osmolality during HHS treatment targets less than 3-8 mOsm/kg/hour reduction to prevent cerebral edema.

Normal saline is appropriate initial fluid in DKA regardless of corrected sodium

Even when corrected sodium reveals underlying hypernatremia in DKA, initial resuscitation uses isotonic saline (0.9% NaCl) to restore intravascular volume and tissue perfusion. Once hemodynamically stable and glucose begins falling, switch to 0.45% NaCl + potassium to provide free water for hypernatremia correction. This sequence prevents both shock (from inadequate initial resuscitation) and renal failure from inadequate volume.

Watch for cerebral edema risk during DKA treatment in children

Children with DKA are at higher risk for cerebral edema during treatment than adults. Risk factors include: severe acidosis (pH below 7.1), low PCO2 at presentation, rapid sodium correction (measured sodium should not fall, corrected sodium should remain stable), excessive fluid administration. Monitor for headache, confusion, bradycardia, hypertension, or unequal pupils — early signs of cerebral edema in pediatric DKA requiring immediate hypertonic saline.

Common Questions About Your Results

For glucose below 400 mg/dL: either 1.6 or 2.4 produces similar results. For glucose above 400 mg/dL: use 2.4 per Hillier et al. (Ann Intern Med 1999), who showed 1.6 underestimates correction by ~40% at severe hyperglycemia. Many institutions and ADA guidelines now recommend 2.4 universally for simplicity. The difference at glucose 500 mg/dL: using 1.6 adds 6.4 mEq/L; using 2.4 adds 9.6 mEq/L — clinically meaningful, especially in HHS with glucose above 1000 mg/dL.

A rising corrected sodium during DKA treatment is abnormal and concerning. It means the patient is losing free water faster than being replaced — possibly from persistent osmotic diuresis, inadequate free water administration, or fever/sweating. Corrected sodium should remain stable or decrease slightly during appropriate DKA management. Rising corrected sodium above 150 mEq/L requires adding free water (switch to 0.45% NaCl or 5% dextrose in saline) and increasing monitoring frequency.

This calculator (corrected-sodium) and the sodium-correction calculator both apply the Katz formula for glucose-driven sodium adjustment. They serve the same purpose. The sodium-correction calculator may also address other correction contexts. Always verify which correction is being applied and ensure the glucose value is current — both sodium and glucose are needed simultaneously for an accurate correction.

No. The Katz formula specifically corrects for glucose-driven osmotic water shift. Severe hypertriglyceridemia or hyperproteinemia can also cause factitious (pseudo)hyponatremia via a different mechanism — lipid/protein occupies plasma volume, reducing water fraction where sodium is measured. These are different phenomena. Osmometry (measuring serum osmolality directly) helps differentiate: pseudohyponatremia from lipemia has a normal osmolal gap; glucose-driven hyponatremia has elevated serum osmolality.

Evidence-Based Methodology

Traditional correction factor 1.6 mEq/L per 100 mg/dL from Katz (NEJM 1973). Revised factor 2.4 mEq/L from Hillier et al. (Ann Intern Med 1999) who found 1.6 underestimates by ~40% at glucose above 400 mg/dL. ADA Clinical Practice Standards (2024) recommend monitoring serum sodium during DKA treatment. Cerebral edema risk and sodium trends: Glaser et al. (NEJM 2001). HHS management: Kitabchi et al. (Diabetes Care 2009). Effective serum osmolality formula and HHS outcomes: Bhardwaj et al. (Crit Care Med 2002).

Clinical Content Trust

Last reviewed:: April 21, 2026
Guideline version:: General evidence framework v2026.04
Source set version:: Primary-source set v1

How to Interpret Your Result

Your corrected sodium value estimates what the serum sodium concentration would be if the blood glucose were at a normal level of 100 mg/dL. If the corrected sodium is within the normal range (135-145 mEq/L), the measured hyponatremia is entirely attributable to the dilutional effect of hyperglycemia, and sodium is expected to normalize as glucose is corrected. If the corrected sodium remains low (below 135 mEq/L), there is a true underlying hyponatremia that needs to be evaluated independently.

Conversely, if the corrected sodium is elevated (above 145 mEq/L), the patient has underlying hypernatremia masked by the dilutional effect of high glucose. This is particularly important in DKA and HHS management because as insulin lowers glucose, water shifts back into cells, and the serum sodium will rise. Failure to recognize underlying hypernatremia can lead to overly rapid sodium changes and risk of osmotic demyelination or cerebral edema.

When to Use This Tool

Use this calculator whenever a patient presents with hyperglycemia (glucose above 100 mg/dL) and an abnormal sodium level, particularly in diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS), and other severe hyperglycemic emergencies. It is essential for accurately assessing a patient's true sodium status before and during insulin therapy.

It is also valuable for monitoring sodium trends during DKA or HHS treatment. As glucose falls with insulin therapy, you can predict how sodium will change. If the corrected sodium is stable or rising appropriately, fluid management is on track. If the corrected sodium is falling, the patient may be receiving excessive free water.

Limitations

The Katz correction factor of 1.6 mEq/L per 100 mg/dL glucose elevation was derived from theoretical modeling and small studies. Some evidence (Hillier 1999) suggests that 2.4 mEq/L per 100 mg/dL is more accurate at glucose levels above 400 mg/dL. Neither correction factor has been rigorously validated in large prospective studies.

The formula assumes a linear relationship between glucose and sodium displacement, which may not hold at extreme glucose levels (above 800-1000 mg/dL). It also does not account for other causes of pseudohyponatremia (such as severe hyperlipidemia or hyperproteinemia) or for concurrent osmotically active substances. In clinical practice, the corrected sodium should be used as a guide alongside serum osmolality, clinical assessment of volume status, and serial monitoring rather than as a standalone decision point.

Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.

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April 21, 2026 · trust-baseline
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Frequently Asked Questions

Elevated blood glucose draws water from cells into the bloodstream by osmosis. This water dilutes the serum sodium, creating a factitious (false) hyponatremia. The measured sodium underestimates the patient's true sodium status. Correcting sodium for glucose reveals the actual sodium level that will become apparent once glucose is normalized with insulin. Without this correction, clinicians may misinterpret sodium and administer inappropriate fluids.

Standard (Katz 1973): Corrected Na = Measured Na + 1.6 × ((Glucose - 100) / 100). Revised (Hillier 1999): Corrected Na = Measured Na + 2.4 × ((Glucose - 100) / 100). The revised formula uses 2.4 mEq/L per 100 mg/dL because empirical studies showed glucose draws more water than the theoretical model predicted at high glucose concentrations. Many clinicians now prefer 2.4 universally for simplicity.

In DKA: corrected sodium is often normal (135-145 mEq/L), confirming hyponatremia is from glucose dilution only. In HHS: corrected sodium is frequently elevated (145-160 mEq/L), revealing significant underlying hypernatremia from profound dehydration. HHS patients with high corrected sodium have large free water deficits requiring careful rehydration with hypotonic fluids. The degree of corrected hypernatremia guides fluid choice and total replacement volume.

Glucose is an osmotically active solute that is largely excluded from cells (except insulin-sensitive tissues). When blood glucose is elevated, glucose creates a higher osmolality in the extracellular space than intracellular space. Water moves down the osmotic gradient from inside cells (intracellular fluid) to outside (extracellular fluid). This increases extracellular volume and dilutes all extracellular solutes, including sodium. For every 100 mg/dL glucose elevation, sodium is diluted by approximately 1.6-2.4 mEq/L.

Normal corrected sodium is 135-145 mEq/L (same as normal serum sodium), since the correction accounts for glucose dilution. If corrected sodium is within normal range in DKA, the patient's apparent hyponatremia is entirely glucose-driven, and sodium will normalize once glucose is treated. If corrected sodium is above 145, the patient has true hypernatremia requiring free water replacement. If corrected sodium is below 135, additional cause of hyponatremia must be sought.

Online Medical Tools — Corrected Sodium

Corrected Sodium

How It Works

Understand why hyperglycemia lowers serum sodium

Apply the Katz correction formula

Interpret corrected sodium to guide DKA and HHS management

Who Uses the Corrected Sodium

Diabetic Ketoacidosis (DKA) Sodium Monitoring

Hyperglycemic Hyperosmolar State (HHS) Severity Assessment

Predicting Sodium Rise During DKA Treatment

Detecting True Hypernatremia Masked by Hyperglycemia

ICU and Perioperative Sodium Management

Pro Tips

Use 2.4 instead of 1.6 for glucose above 400 mg/dL

Track corrected sodium during DKA treatment, not just measured sodium

HHS corrected sodium predicts free water deficit

Distinguish glucose-driven dilutional hyponatremia from SIADH

Calculate effective serum osmolality to predict symptoms

Normal saline is appropriate initial fluid in DKA regardless of corrected sodium

Watch for cerebral edema risk during DKA treatment in children

Common Questions About Your Results

Evidence-Based Methodology

Clinical Content Trust

How to Interpret Your Result

When to Use This Tool

Limitations

Changelog

Related Tools

Sodium Correction

Serum Osmolality

Anion Gap

Further Reading

A Complete Guide to Clinical Laboratory Medicine: Understanding Key Tests and Calculations

Frequently Asked Questions