How the MELD-Na Score Works (With a Worked Example)
MELD-Na is a score from 6 to 40 that measures how severe a patient’s chronic liver disease is, calculated from bilirubin, creatinine, INR, and serum sodium. It is the number transplant programs use to rank patients on the liver waiting list: the higher the score, the sicker the patient and the higher their priority for a transplant.
This guide walks through the formula step by step, shows a full worked example with real lab values, gives you the severity bands, and flags the one data-entry mistake that trips up almost everyone who calculates this score by hand.
The formula, step by step
MELD-Na is built in two stages. First you calculate a base score called MELD(i) from three lab values, then you adjust it for sodium.
Step 1: base MELD. Bilirubin and INR are floored at 1.0, meaning any measured value below 1.0 is treated as 1.0 in the formula. This exists because the natural log of a number under 1 is negative, and the model was never built to let a lab value below normal subtract points from the score. Creatinine is also floored at 1.0, but it is additionally capped at 4.0. If the patient has had dialysis (two or more sessions, or 24 hours of continuous therapy) in the past week, creatinine is forced to 4.0 regardless of what the lab actually measured, on the assumption that dialysis is already masking the true severity of kidney failure.
With those three values in hand, the base score is:
MELD = round( 10 × [ 0.957×ln(creatinine) + 0.378×ln(bilirubin) + 1.12×ln(INR) + 0.643 ] )
Step 2: the sodium correction. This only applies when the base MELD comes out above 11. Sodium itself is clamped to a range of 125 to 137 mmol/L before it goes into the formula, so a very low reading like 118 is treated as 125, and a reading above 137 is treated as 137. The correction is:
MELD-Na = MELD + 1.32×(137 − Na) − 0.033×MELD×(137 − Na)
The result is rounded to the nearest whole number and clamped to the overall 6 to 40 range. If the base MELD is 11 or lower, none of this runs, the final score is simply the base MELD (with 6 as the floor).
This is the UNOS/OPTN 2016 version of MELD-Na, and it is worth being precise about that, because it is not the same model as MELD 3.0, a 2021 revision that adds albumin and sex to the equation and uses different coefficients. If your transplant program has already switched to MELD 3.0, expect this tool’s number to differ slightly from theirs; they are answering a related but distinct question.
Worked example
Take a patient with bilirubin 2.0 mg/dL, creatinine 1.5 mg/dL, INR 1.3, and sodium 130 mmol/L, no dialysis in the past week.
| Lab value | Result | Role in the formula |
|---|---|---|
| Bilirubin | 2.0 mg/dL | used as-is (above the 1.0 floor) |
| Creatinine | 1.5 mg/dL | used as-is (no dialysis, within the 1.0 to 4.0 range) |
| INR | 1.3 | used as-is (above the 1.0 floor) |
| Sodium | 130 mmol/L | within the 125 to 137 clamp range |
| Base MELD | 16 | |
| MELD-Na (after sodium correction) | 22 |
The base score from bilirubin, creatinine, and INR alone comes out to 16. Because that is above 11, the sodium correction kicks in, and because 130 mmol/L is below the normal range, the correction adds points rather than subtracting them, six in this case, pushing the final MELD-Na to 22. That lands the patient in the “high” severity band. Sodium is the part of this score people forget matters: two patients with identical bilirubin, creatinine, and INR can land in different severity bands purely because one of them is hyponatremic.
Calculate it with your own values
Score bands
| Score range | Band | Notes |
|---|---|---|
| 6 to 9 | Low | 6 is the lowest possible score, not 0 |
| 10 to 19 | Moderate | |
| 20 to 29 | High | |
| 30 to 40 | Very high | 40 is the highest possible score |
At the low end, take a patient with bilirubin 1.0, creatinine 1.0, INR 1.0, and sodium 137, no dialysis. Every input sits at the best possible value, so the base MELD comes out to 6, which is not above 11, so no sodium correction applies. The final score is 6, the floor of the entire scale. Band: low.
At the very-high end, take a patient with bilirubin 8.0, creatinine 3.0, INR 2.5, and sodium 126, no dialysis. The base MELD is 35, and the sodium correction (126 is well below normal) pushes it up to 37. Band: very high.
Common mistakes
Mishandling the dialysis checkbox. This is the single most common error with MELD-Na, and it can move a patient a full severity band without a single lab value actually changing. Consider a patient with bilirubin 2.0 mg/dL, INR 1.3, sodium 134 mmol/L, and a measured creatinine of 1.0 mg/dL.
- If the dialysis checkbox is left unticked, creatinine of 1.0 is used as-is: base MELD comes out to 12, and MELD-Na is 15. That lands in the moderate band.
- If the checkbox is ticked, because the patient actually had two or more dialysis sessions in the past week, creatinine is forced to 4.0 regardless of the 1.0 reading: base MELD jumps to 25, and MELD-Na is 26. That lands in the high band.
Same bilirubin. Same INR. Same sodium. The only thing that changed is one checkbox, and the score jumped 11 points, moving the patient from moderate to high severity. Get the dialysis history wrong in either direction, either forgetting to tick it for a patient who was dialyzed, or ticking it for one who wasn’t, and you have materially misrepresented how sick that patient is.
Forgetting the sodium clamp. A sodium of 118 does not get used as 118. It is pulled up to the 125 floor before the correction runs. Plugging in the raw, unclamped value by hand produces a score that does not match what the formula actually specifies.
Confusing MELD-Na with MELD 3.0. As mentioned above, MELD 3.0 adds albumin and sex to the model and uses its own coefficients. It is a different (newer) score, not a rebranding of MELD-Na, and the two will not always agree on the same patient.
Using it outside its validated age range. MELD-Na applies to patients aged 12 and older. Pediatric liver disease severity is scored with PELD, a separate model built for children.
Frequently asked questions
What labs do I need to calculate MELD-Na?
Four values: total bilirubin (mg/dL), creatinine (mg/dL), INR, and serum sodium (mmol/L), plus whether the patient has had dialysis in the past week. All four labs should ideally be drawn close together, since the score reflects a snapshot of liver and kidney function at one point in time.
Why does the sodium correction only apply above a base MELD of 11?
The original UNOS/OPTN model found that sodium only meaningfully improved prediction of mortality risk once a patient’s baseline disease severity was already at a moderate level or higher. Below that threshold, sodium adds statistical noise rather than useful information, so the formula skips the correction entirely for base scores of 11 or below.
Can MELD-Na go above 40 or below 6?
No. Both the base MELD and the final MELD-Na are clamped to a 6 to 40 range regardless of how the raw math works out. A patient with catastrophically abnormal labs still reports as 40, not some higher theoretical number.
Is a higher MELD-Na score always worse?
Yes, within the scope of what it measures. It reflects a higher predicted short-term mortality risk from liver disease and, correspondingly, higher priority on the transplant waiting list. It is not a diagnosis and it does not capture every factor a transplant team weighs, such as the specific cause of liver disease or a patient’s overall functional status.
Should I use this score to make a treatment decision?
No. This calculator is an estimate meant to support transplant-allocation discussions and to help you understand how the score is built, not a substitute for a hepatologist or transplant team reviewing the full clinical picture. Always confirm scores that affect real patient care against your program’s official calculation and lab values.