Newborn Jaundice Risk Calculator
Gives safe next-step guidance for a newborn's bilirubin result based on age in hours, gestational age and risk factors. It flags jaundice in the first 24 hours and points to the AAP 2022 hour-specific phototherapy thresholds, which a clinician must apply.
Last updated: September 2026
Formula below · 3 sources (aap.org, healthychildren.org, Wikipedia) · Updated Sep 2026
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About this calculator
Neonatal jaundice occurs when total serum bilirubin (TSB) accumulates faster than the liver can conjugate and excrete it. Whether a level is dangerous depends on the baby's exact age in hours, gestational age and neurotoxicity risk factors (such as gestational age under 38 weeks, hemolysis, G6PD deficiency, sepsis or significant illness). The 2022 American Academy of Pediatrics guideline (for babies born at 35 weeks or later) gives hour-specific phototherapy and escalation-of-care thresholds for each gestational week, with lower thresholds when risk factors are present; clinicians plot the TSB on those curves (for example with the BiliTool or PediTools calculators). This calculator does not reproduce those curves (a simple 'risk score' cannot, and could look falsely reassuring), so it returns guidance instead: jaundice or a raised bilirubin in the first 24 hours always needs same-day medical assessment; below 35 weeks the neonatal team's thresholds apply; otherwise the result reminds you to have the value plotted on the AAP 2022 chart. Any baby who is very sleepy, feeding poorly, has a high-pitched cry or arching, or whose yellow colour is spreading needs urgent care regardless of the number.
How to use
Example: a 36-hour-old baby born at 38 weeks has a bilirubin of 8 mg/dL with no risk factors. Enter 8, 36, 38 and Low Risk. The calculator reminds you that 8 mg/dL at 36 hours must be compared with the AAP 2022 phototherapy threshold for 38 weeks, which the baby's clinician does with the hour-specific chart. If the same baby were 20 hours old, the result would say the baby needs medical assessment today, because jaundice in the first day of life is never normal.
Frequently asked questions
What bilirubin level is dangerous for a newborn?
Danger thresholds depend heavily on the baby's age in hours and gestational age. For a full-term baby at 48 hours, most guidelines (AAP Bhutani nomogram) flag levels above 18 mg/dL as high risk; at 24 hours, even 12 mg/dL warrants urgent evaluation. Premature infants have lower thresholds — a 35-week baby may need phototherapy at levels that would be acceptable in a full-term newborn. This calculator does not compute a risk score; clinical decisions must be made using the validated AAP 2022 thresholds and physician judgment.
What risk factors make newborn jaundice more serious?
Factors that accelerate bilirubin production or impair elimination significantly raise risk. Hemolytic conditions — ABO or Rh blood group incompatibility, G6PD deficiency, and hereditary spherocytosis — are among the most dangerous because they cause rapid bilirubin rise. Bruising from a difficult delivery or cephalohematoma adds extra bilirubin load as blood breaks down. Prematurity (< 37 weeks) reduces hepatic conjugation capacity. East Asian ethnicity and exclusive breastfeeding with poor latch and low intake are also recognized risk factors in AAP guidelines. Combinations of these factors compound the risk substantially.
When should I take my newborn to the doctor for jaundice?
You should seek same-day medical evaluation if your newborn appears yellow in the first 24 hours of life, or if yellow color spreads below the belly button or into the arms and legs. Other warning signs include extreme sleepiness (hard to wake for feeds), poor feeding, high-pitched cry, or arching of the back. The AAP recommends that all newborns be assessed for jaundice before hospital discharge and have a follow-up visit within 1–2 days if discharged before 72 hours of age. Do not rely solely on visual inspection — only a bilirubin blood test or transcutaneous meter gives an accurate level.