Corrected Sodium, Deficiency
& Intake Calculator
Correct serum sodium for hyperglycemia using both the Katz and Hillier formulas side-by-side, and interpret hyponatremia or hypernatremia.
| Sodium (mEq/L) | Category | Notes |
|---|---|---|
| Below 120 | Severe Hyponatremia | Medical emergency — seizure/brain swelling risk |
| 120 – 134 | Hyponatremia | Requires medical evaluation |
| 135 – 145 | Normal | Standard reference range |
| 146 – 159 | Hypernatremia | Often reflects dehydration |
| 160+ | Severe Hypernatremia | Medical emergency |
Reference ranges vary slightly by laboratory — always interpret alongside your lab's own reported range and full clinical picture.
What Is Corrected Sodium and Why Hyperglycemia Changes the Picture
Two correction formulas dominate clinical use: Katz (1973), which adds 1.6 mEq/L to sodium for every 100 mg/dL glucose is above 100 mg/dL, and Hillier (1999), which uses a higher factor of 2.4 mEq/L, based on research suggesting the original Katz factor underestimates the true correction, especially when glucose exceeds 400 mg/dL. This calculator deliberately shows both results side-by-side, rather than picking one, since genuine clinical practice still uses both depending on context and severity.
Katz vs Hillier: Which Formula Should You Trust?
📐 Katz Formula (1973)
The original, most widely used correction factor in routine clinical practice. Simple, well-established, but research suggests it may underestimate the true correction at very high glucose levels.
📊 Hillier Formula (1999)
A recalibrated factor based on experimental data, generally considered more accurate — particularly for glucose levels above 400 mg/dL, such as in diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS).
In practice, many clinicians use Katz for routine, moderately elevated glucose and lean toward Hillier for severe hyperglycemia, though neither formula is universally mandated — this is genuinely an area of accepted clinical variation rather than a single settled answer, which is exactly why showing both values, rather than forcing a single "correct" number, gives a more honest and clinically useful picture than a calculator that only offers one formula.
Worked Example
Consider a patient with a measured sodium of 128 mEq/L and glucose of 500 mg/dL. Using Katz: 128 + 1.6 × (500-100)/100 = 128 + 6.4 = 134.4 mEq/L. Using Hillier: 128 + 2.4 × (500-100)/100 = 128 + 9.6 = 137.6 mEq/L. Notice that the Katz-corrected value (134.4) still falls just below the normal range and would be classified as mild hyponatremia, while the Hillier-corrected value (137.6) falls within the normal range entirely — a meaningful difference in interpretation that illustrates exactly why the choice of formula genuinely matters at higher glucose levels, and why reviewing both values together, as this calculator does, is more informative than relying on a single formula's output in isolation.
Understanding Hyponatremia and Hypernatremia
A normal serum sodium level is generally 135-145 mEq/L (mmol/L). Hyponatremia (low sodium, below 135) can cause headache, confusion, nausea, and in severe cases (generally below 120-125 mEq/L), seizures and dangerous brain swelling — this level is considered a medical emergency requiring prompt treatment. Hypernatremia (high sodium, above 145) often reflects dehydration and can cause thirst, confusion, and in severe cases (above 160), seizures and altered consciousness as well. Both directions of sodium imbalance can have numerous underlying causes — from medications and kidney function to fluid balance and hormonal factors — which is exactly why a single corrected sodium value should always be interpreted alongside a fuller clinical picture rather than in isolation.
The History Behind These Two Formulas
The Katz formula emerged from a relatively simple physiological calculation published as a brief communication in the New England Journal of Medicine in 1973, based on theoretical osmotic principles rather than extensive clinical validation data at the time. It became the default clinical standard largely because of its simplicity and early adoption, remaining the figure most commonly taught and cited for decades. The Hillier formula, by contrast, emerged from an actual clinical study — published in the American Journal of Medicine in 1999, using data from patients undergoing controlled glucose infusion to directly measure how sodium actually changed as glucose rose, rather than relying purely on theoretical calculation. This empirical grounding is part of why many clinicians consider Hillier's 2.4 factor more accurate, particularly at the glucose extremes common in diabetic ketoacidosis and hyperosmolar hyperglycemic state, even though Katz remains more commonly referenced in general practice due to its longer history of use.
Why This Matters Most in DKA and HHS
Sodium correction for hyperglycemia becomes most clinically important in two specific emergency presentations: diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), both of which involve very high glucose levels — often well above 400-600 mg/dL — precisely the range where the Katz and Hillier formulas diverge most noticeably, as illustrated in the worked example above. In these settings, an inaccurately low apparent sodium reading (before correction) could lead to inappropriate fluid or electrolyte management decisions, which is exactly why understanding both correction options, and why they can meaningfully disagree at extreme glucose levels, genuinely matters rather than being an academic curiosity. If glucose is markedly elevated, our Blood Sugar Checker can help provide additional context on glucose severity alongside this sodium correction.
Common Causes Worth Knowing
- Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) — the classic clinical scenarios where sodium correction for glucose becomes clinically essential
- Certain diuretics — can contribute to true hyponatremia independent of glucose effects
- Excess free water intake or SIADH — can dilute sodium through a completely different mechanism than glucose
- Significant dehydration or diabetes insipidus — common causes of hypernatremia
- Repeat testing matters — sodium will shift as glucose is treated and normalizes, so a single corrected value is a snapshot, not a final answer
How This Differs From Your Dietary Sodium Target
It's worth being clear that this tool addresses a completely different question than "how much sodium should I eat?" — that's a dietary intake question, answered by comparing your daily salt consumption against AHA and NHS guidelines. This tool instead interprets a blood test result, reflecting your body's current sodium balance and hydration status, which is influenced by far more than diet alone (kidney function, medications, fluid intake, and underlying health conditions all play a role). If you're specifically looking for daily dietary sodium guidance, our Sodium Intake Calculator covers that separately.
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