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 use this as a teaching aid and a rough orientation, and use your unit’s current nomogram 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 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.

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.

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.

The rate matters as much as the height. A rise faster than about 0.2 mg/dL per hour suggests hemolysis and changes the plan regardless of where the level currently sits.

Exchange transfusion thresholds run roughly 5 mg/dL above the phototherapy line. 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.