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By the Peanutbean parent · checked against CDC, NHS and AAP guidance · how we fact-check

Newborn jaundice: why so many babies turn yellow, and when it matters

Last verified: July 14, 2026

The short answer: a yellow tint in the first week is one of the most normal things a newborn can do. It peaks around day 3, usually fades by 2 weeks, and most babies need no treatment beyond frequent feeds. The exceptions are specific and worth knowing: yellow in the first 24 hours, a baby who is hard to wake or feeding poorly, dark pee, or pale poo. Those need a doctor promptly.

If your baby looked pink in the delivery room and faintly yellow two days later, nothing went wrong. Here is what is happening and how to tell the normal version from the version that needs attention.

Why it happens

Everyone’s blood contains a waste product called bilirubin, which comes from red blood cells and is cleared by the liver. Before birth, your liver did that job for your baby. After birth, the baby’s own liver takes a few days to get up to speed, so bilirubin builds up in the meantime and tints the skin and eyes yellow (AAP: Jaundice in Newborns).

That is the ordinary version, and it is not a sign of another health problem. Rarer causes exist, such as a blood-type mismatch between mother and baby, an infection, or a liver condition, which is one reason the checks in the first days matter (NHS: Jaundice in babies).

What it looks like

The yellow usually shows first in the face and the whites of the eyes, then moves down to the chest, tummy, arms and legs as the level rises. You might also see it under the tongue or inside the cheeks. It is easiest to spot in daylight, and gently pressing the tip of the nose or the forehead can make it easier to see. On black or brown skin the yellow can be much harder to spot, so the eyes, gums, pee and poo are the more reliable places to look (NHS, AAP).

The usual timeline: most visible around day 3, gone in about 2 weeks. Breastfed babies often stay faintly yellow for longer, commonly up to a month, and that on its own is not a problem (NHS, AAP).

The checks every baby gets

You do not have to eyeball this alone. Your care team checks for jaundice in the first days, and every baby should have at least one bilirubin measurement before leaving the hospital, either a blood test or a special light pressed on the skin. Babies discharged before 48 hours should usually be seen again within 2 days (AAP, NHS).

Some babies need an earlier follow-up: a high level before discharge, birth more than 2 weeks early, jaundice in the first 24 hours, breastfeeding that is not going well yet, a lot of bruising from the delivery, or an older sibling who needed light therapy. If any of those fit, ask about the follow-up plan before you leave the hospital (AAP). Babies born early are generally more prone to jaundice; our preemie homecoming guide covers those first weeks.

What actually helps: feeding, feeding, feeding

The treatment for ordinary jaundice is mostly milk. Feeding around 8 to 12 times a day helps the body flush bilirubin out, so if your baby is sleepy, wake them for feeds (NHS).

Jaundice is a little more common in breastfed babies, most often when milk is not flowing well yet, and that is worth saying without guilt: in the first 24 hours a normal breastfed newborn gets only about a teaspoon of milk per feed, and the amount builds day by day. Frequent feeds build your supply and keep bilirubin down at the same time. If feeding is hard, ask your midwife, doctor or a lactation specialist early rather than late (AAP).

One myth to retire: putting your baby in sunlight is not a safe way to treat jaundice (AAP). Which brings us to what doctors use instead.

If treatment is needed

When the level is high enough to treat, the standard is phototherapy: your baby lies undressed in a cot under special blue-green light that helps break bilirubin down. It usually takes around 48 hours, typically in hospital, though home equipment is sometimes an option. In some breastfed babies, topping up with formula for a short time can help bring the level down. Very high levels are treated urgently in hospital, rarely with a special blood transfusion (NHS, AAP).

The honest context for the scary-sounding part: untreated, extremely high bilirubin can harm the brain. That outcome is rare precisely because of the routine, slightly tedious checking described above. The system is built so the dangerous version gets caught early (AAP).

When to call, exactly

Ask for an urgent GP or midwife appointment, or call 111, if your baby is more than 24 hours old and you think they have jaundice, if diagnosed jaundice is not improving or is getting worse, or if their pee is dark yellow or brown, or their poo is a pale creamy colour. Keep a sample of the poo to show the doctor; our baby poop guide explains why pale poo is one of the colours that always matters (NHS).

Call 999 or go to A&E if your baby has jaundice and any of these (NHS):

• is under 24 hours old
• is sleepier than normal or hard to wake
• is not feeding, or has produced no wet nappies
• is floppy or stiff, or has jerking or twitching movements
• has a temperature of 38C or more, or 36C or less
• has difficulty breathing, grunting, or the stomach sucking in under the ribs

Also tell the doctor about jaundice that overstays: more than 2 weeks in a formula-fed baby, more than 4 weeks in a breastfed one (AAP). And as always: your own concern is reason enough to call.

Keep reading

• Is my baby’s poop normal?
• Weeks 0 to 8: settling in
• Bringing your preemie home from the NICU
• All the first-year windows

Sources

• NHS: Jaundice in babies (page last reviewed March 2026)
• AAP: Jaundice in Newborns (last updated August 2024)

Peanutbean provides general information for educational purposes only. It is not medical advice. Every baby develops at their own pace. Always talk to your pediatrician about your child’s health.