Neonatal Bilirubin Calculator

Neonatal jaundice (hyperbilirubinemia) is the most common condition requiring medical evaluation in newborns. About 60% of term and 80% of preterm babies develop jaundice in the first week. Most cases are benign physiologic jaundice; a small fraction can progress to bilirubin-induced neurological dysfunction if untreated.

Read this before using the numbers below

These thresholds are the AAP 2004 guideline. The American Academy of Pediatrics issued revised hyperbilirubinemia guidance in 2022, which raised phototherapy thresholds and restructured them by gestational age in weekly steps with a separate neurotoxicity risk-factor flag, rather than the three-band grouping used here. A baby treated to the 2004 lines may be treated earlier than current practice requires.
So the page says “above the 2004 line” rather than “phototherapy needed”, and the line it draws is a conservative one. Use it as a teaching aid and a rough orientation, and use your unit’s current chart for any real decision. On a newborn, the difference between the two guidelines is a real clinical difference, not a rounding detail.

Risk factors that move an infant into a higher band in the 2004 guideline include isoimmune hemolytic disease, G6PD deficiency, asphyxia, significant lethargy, temperature instability, sepsis, metabolic acidosis, and serum albumin below 3 g/dL.

AAP 2004 phototherapy thresholds, infants 35+ weeks gestation:

The real guideline is a continuous curve, and the table gives four points on it. This calculator interpolates straight lines between those points rather than stepping, because a step function jumps by 3 mg/dL the moment a baby turns 48 hours old, and a baby at 47 hours is not meaningfully different from one at 49.

Outside the United States bilirubin is usually reported in µmol/L. One mg/dL is 17.1 µmol/L, so the 15 mg/dL line is about 257 µmol/L. Pick the unit your result came in; the page converts.

What the 2022 revision changed, besides the numbers

• Neurotoxicity risk factors are now gestational age under 38 weeks, albumin under 3.0 g/dL, isoimmune or other hemolytic disease (G6PD deficiency included), sepsis, and significant clinical instability in the previous 24 hours.
• A rapid rise points to hemolysis: 0.3 mg/dL an hour or more in the first 24 hours, or 0.2 an hour or more after that. Enter an earlier result and the page works out the rate for you.
• Care is escalated when the bilirubin comes within 2 mg/dL of the exchange transfusion line, rather than waiting to cross it.
• A skin (transcutaneous) reading is confirmed with a blood test when it is within 3 mg/dL of the phototherapy line or 15 mg/dL or more.
• The direct (conjugated) part of the bilirubin is not subtracted from the total.

Jaundice in the first 24 hours is never normal

Below 24 hours the calculator holds the 24-hour value, and that is deliberately the wrong question to be asking. Visible jaundice appearing in the first day of life is pathological by definition, usually hemolytic, and needs urgent evaluation whatever the number is. Do not use a threshold to reassure yourself there.

At the other end, jaundice still visible at two weeks (three in a baby born preterm) is prolonged jaundice. It needs a conjugated bilirubin, to rule out a liver cause such as biliary atresia, and these lines no longer apply.

How bilirubin behaves

It rises naturally over the first 3 to 5 days, peaking as the liver’s conjugation capacity catches up, then falls. A level above threshold does not by itself mean something is wrong with the baby. It means the height or the rate of rise warrants acting before it can do harm.

Exchange transfusion thresholds in the 2004 charts run roughly 5 mg/dL above the phototherapy line, a little more in the first day. Within 2 to 3 mg/dL of the phototherapy threshold, a repeat measurement in 4 to 8 hours is usual.

This tool is for education. Clinical decisions for newborns need direct physician evaluation and the whole picture: feeding, weight loss, blood group, direct antiglobulin test, and how the baby looks.