Newborn · Jaundice
Newborn Jaundice & Bilirubin
Why most newborns turn yellow, when it's normal, when it's serious. NICE bilirubin nomogram, phototherapy explained, breastfeeding vs breast milk jaundice, home phototherapy. NICE CG98.
Last reviewed 2 June 2026
AAP 2022 newborn bilirubin nomogram
Phototherapy threshold — neonatal jaundice
h
wk
mg/dL
Enter postnatal age, gestational age, and bilirubin to see the phototherapy line.
Why is my newborn yellow?
Jaundice from BILIRUBIN (yellow pigment from breakdown of old red blood cells). Newborns have lots of red cells at birth; their liver is still maturing and can’t clear bilirubin fast enough.
~60% of full-term newborns visibly jaundiced. Usually peaks day 3-5; resolves over 1-2 weeks. Normal physiological jaundice = harmless.
When to worry — red flags
- Jaundice within first 24 hours — always abnormal.
- Rapidly darkening yellow.
- Jaundice in feet / palms (severe).
- Baby lethargic, not feeding well.
- High-pitched cry, arched back, fever (late kernicterus — emergency).
- Pale stool + dark urine (bile duct issue).
- Jaundice persisting >14 days term / >21 days preterm.
Call midwife / GP same day for any of these.
How bilirubin is measured
- Transcutaneous (TcB): handheld light meter; non-invasive; screening.
- Serum (SBR): heel-prick blood test; accurate; for treatment decisions.
Plotted on age-specific NICE nomogram. Above treatment line = phototherapy. Above exchange line = serious.
What is phototherapy?
Special blue light (425-475 nm) shone on baby’s skin. Converts bilirubin to water-soluble form excreted in urine + stool. Not UV; safe.
- Baby in nappy-only for max skin exposure.
- Eye shades protect eyes.
- Under lights or on biliblanket (fibreoptic, lets you hold).
- 15-30 min breaks for feeding every 2-3h.
- Duration usually 1-3 days.
Risk factors for severe jaundice
- Preterm (immature liver).
- Asian ethnicity (slightly higher).
- Blood group incompatibility (Rh, ABO).
- Haemolysis (G6PD, spherocytosis).
- Infection.
- Bruising / cephalohaematoma.
- Maternal diabetes.
- Delayed feeding / dehydration.
- Sibling with severe jaundice.
Physiological vs pathological
- Physiological: day 2-3 onset, peaks 3-5, resolves 1-2 weeks. Normal.
- Pathological: day 1 onset; rapid rise; persists >2 wk term; pale stool + dark urine; baby unwell. Investigate.
Breastfeeding and jaundice
- Breastfeeding jaundice (early): from insufficient intake; fix with MORE FREQUENT feeding.
- Breast milk jaundice (late): peaks 2-3 weeks, lasts up to 12. Rarely needs treatment. Continue breastfeeding.
Different scenarios
Scenario 1: Day 3 mild yellow, feeding well
Likely physiological. TcB if concern; SBR if rising. Continue frequent feeding.
Scenario 2: Day 1 jaundiced, blood group incompatibility
Pathological. Urgent SBR + Coombs test. Likely phototherapy.
Scenario 3: SBR above treatment line at 48h
Phototherapy. Biliblanket if low-moderate risk; lights if high. Continue feeding.
Scenario 4: Above exchange line at 72h despite phototherapy
Intensive phototherapy. Exchange transfusion consideration. NICU.
Scenario 5: 3 weeks old, still mildly jaundiced, breastfed
Likely breast milk jaundice. Rule out pathological (split bilirubin to check conjugated; LFTs). Continue feeding.
Care guidance — jaundice
- Check skin in natural daylight.
- Jaundice progresses head to toe; feet = severe.
- Day 1 jaundice = always assess.
- Phototherapy is safe + effective.
- Continue breastfeeding (frequent feeds help).
- Biliblanket home option in some areas.
- Watch for lethargy, poor feeding, fever.
- Persisting >14 days needs investigation.
Sources
- NICE CG98. Jaundice in newborn babies under 28 days.
- AAP Clinical Practice Guideline (2022). Hyperbilirubinemia in the newborn.
- Bhutani VK, et al. Hour-specific bilirubin nomogram.
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Frequently asked questions
Why is my newborn yellow?
JAUNDICE — yellow tinge of skin / eyes — from BILIRUBIN (yellow pigment from breakdown of old red blood cells). NEWBORN BABIES make lots of bilirubin because they have lots of red cells at birth that break down. Baby's LIVER is still maturing and can't clear bilirubin fast enough. RESULT: visible jaundice in ~60% of full-term newborns. USUALLY PEAKS day 3-5; resolves over 1-2 weeks. NORMAL physiological jaundice = harmless. BUT high levels need treatment to prevent BRAIN DAMAGE (kernicterus).
When should I worry about jaundice?
RED FLAGS: (1) JAUNDICE within FIRST 24 HOURS of life — always abnormal; (2) RAPIDLY DARKENING yellow; (3) JAUNDICE in feet / palms (severe — yellow progresses head to toe); (4) BABY LETHARGIC, not feeding well; (5) HIGH-PITCHED CRY, arched back, fever — late kernicterus signs (medical emergency); (6) PALE STOOL + DARK URINE (suggests bile duct issue, not just physiological); (7) JAUNDICE persisting >14 DAYS in term baby / >21 DAYS preterm — investigate. CALL midwife / GP same day for any of these.
How is bilirubin measured?
(1) TRANSCUTANEOUS BILIRUBINOMETER (TcB) — handheld light meter on forehead/chest; non-invasive; SCREENING only; quick. (2) SERUM BILIRUBIN (SBR) — heel-prick blood test; ACCURATE; for treatment decisions. PLOTTED on AGE-SPECIFIC NOMOGRAM (Bhutani / NICE chart) — age in hours + bilirubin level. ABOVE TREATMENT LINE = phototherapy. ABOVE EXCHANGE LINE = much more serious. AT TERM, treatment thresholds rise through first few days, then plateau.
What is phototherapy?
TREATMENT for high bilirubin. SPECIAL BLUE LIGHT (425-475 nm) shone on baby's skin. Converts bilirubin to water-soluble form that can be excreted via urine + stool. NOT UV (no skin damage). BABY PLACED under lights (in incubator usually) OR ON BILIBLANKET (fibreoptic blanket under baby, lets you hold). NAPPY-ONLY for maximum skin exposure; EYE SHADES protect baby's eyes. CONTINUOUS or with breaks for feeding. DURATION usually 1-3 days. SAFE; very effective (lowers bilirubin within hours).
Can I still hold and feed during phototherapy?
BREAKS for feeding usually allowed (15-30 min off every 2-3 hours). BABY NEEDS to be under lights majority of time for effectiveness. BREASTFEEDING during phototherapy: HELPFUL (more feeds = more stool = more bilirubin excreted). BILIBLANKET option allows skin-to-skin + breastfeeding while undergoing treatment. PUMPING + bottle-feeding option for very ill / NICU babies. PARENTAL stress real; talk to staff.
Why does my baby need light treatment if jaundice is normal?
HIGH bilirubin can cross blood-brain barrier and cause permanent BRAIN DAMAGE (KERNICTERUS / acute bilirubin encephalopathy). RARE in modern NHS — but real. RISK depends on absolute level + risk factors (preterm, sepsis, low albumin, haemolysis). TREATMENT thresholds intentionally CONSERVATIVE — better to over-treat with safe phototherapy than risk neurological damage. EXCHANGE TRANSFUSION (much more serious procedure) reserved for very high levels not responding to phototherapy.
What's exchange transfusion?
EMERGENCY procedure for VERY HIGH bilirubin (above NICE exchange line) or rapid rise despite intensive phototherapy. BABY'S BLOOD REPLACED gradually with donor blood — usually 2x baby's blood volume exchanged. REMOVES bilirubin + replaces with healthy red cells. INVASIVE: umbilical catheters; ICU-level monitoring. RISKS: infection, electrolyte disturbances, embolism. RARE in modern UK with effective phototherapy. EFFECTIVE when needed; prevents kernicterus.
Why is my baby more jaundiced than others?
RISK FACTORS: (1) PRETERM (immature liver — main reason); (2) ASIAN ethnicity (slightly higher risk); (3) BLOOD GROUP INCOMPATIBILITY — Rh-isoimmunisation, ABO incompatibility; (4) HAEMOLYSIS (G6PD deficiency, hereditary spherocytosis); (5) INFECTION; (6) BRUISING / cephalohaematoma from birth; (7) MATERNAL DIABETES; (8) DELAYED FEEDING / dehydration; (9) SIBLING with severe jaundice; (10) BREASTFEEDING jaundice (subset). KNOWN RISK = closer monitoring.
What's the difference between physiological and pathological jaundice?
PHYSIOLOGICAL: STARTS DAY 2-3, peaks day 3-5, resolves 1-2 weeks. Normal lab. Most babies. PATHOLOGICAL: STARTS DAY 1 (within 24h); rises rapidly; very high level; persists >2 weeks term / 3 weeks preterm; PALE STOOL + DARK URINE; baby unwell. CAUSES: haemolysis (blood incompatibility, G6PD), infection (sepsis, UTI), congenital (biliary atresia — needs URGENT diagnosis < 8 weeks!), metabolic (Crigler-Najjar, galactosaemia). PATHOLOGICAL needs investigation + treatment.
What about breastfeeding jaundice?
TWO TYPES: (1) BREASTFEEDING JAUNDICE (early) — first week; due to INSUFFICIENT INTAKE → more bilirubin retained; fix by MORE FREQUENT FEEDING + supplements if dehydrated. (2) BREAST MILK JAUNDICE (late) — peaks 2-3 weeks; lasts up to 12 weeks; due to substances in breast milk slowing bilirubin metabolism. RARELY needs treatment; CONTINUE breastfeeding (DON'T stop!). Both diagnoses of exclusion — rule out pathological causes first. BREASTFED BABIES tend to be slightly more jaundiced than formula-fed normally — minimal.
How often does baby's bilirubin get checked?
ROUTINE at: NHS — at risk based on TcB if jaundiced; SOME UK hospitals universal pre-discharge bilirubin check. EXAMINATION: jaundice visible if SBR ≥85 µmol/L. IF JAUNDICED early: hourly observation, repeat TcB / SBR; nomogram plotting. HIGH RISK group (preterm, hemolytic, bruising, sepsis): more frequent. POST-DISCHARGE: parents told to check skin colour daily; CALL midwife if more yellow, lethargic, poor feeding.
Can I check jaundice at home?
VISUAL CHECK: gentle press of forehead / nose / sternum / belly with finger; observe colour underneath in natural daylight. PROGRESSION head-to-toe (jaundice spreads top-down — feet involvement = severe). NOT RELIABLE for level — call midwife if uncertain. TcB devices at home not usually available; some private services offer. NHS comes to you for follow-up if at-risk.
Will jaundice affect my baby long-term?
TREATED JAUNDICE: NO long-term effects. UNTREATED severe jaundice: KERNICTERUS — permanent brain injury (cerebral palsy, deafness, learning disability, vision issues). RARE in NHS with screening + treatment. MILD physiological jaundice: completely harmless; resolves naturally. STUDIES no long-term cognitive impact at properly-managed levels. CONFIDENCE in modern NHS treatment is high.
What about home phototherapy?
AVAILABLE in some UK areas. BILIBLANKET (fibreoptic) device sent home with you; baby wears underneath clothing; less restrictive than incubator. MIDWIFE visits to check bilirubin daily. ALLOWS family bonding + breastfeeding. APPROPRIATE for: less severe cases; lower-risk babies; close monitoring available. NOT for: very high bilirubin; very preterm; medical complications. ASK your trust about availability.
How does this relate to other calculators on BumpBites?
Companion: /calculators/phototherapy-rebound for after-treatment risk; /calculators/bilirubin-exchange for exchange transfusion thresholds; /calculators/anti-d-dosing (Rh disease prevention); /calculators/breastfeeding-latch (feeding helps clear bilirubin); /calculators/newt-weight-loss (dehydration → jaundice); /calculators/newborn-skin.