How do you know when your milk comes in?

When does your milk come in?

Milk comes in anywhere between the second and fifth day after the birth - which may be later than you have heard. Most women's milk comes in about 30 to 40 hours after the placenta is delivered, regardless of what is happening with the breastfeeds. You can find out what happens in your breast to make your milk comes in here.

But milk can take up to five days to come in for mothers whose newborns remain healthy and safe, and who go on to exclusively breastfeed. Milk often comes in slower for your firstborn, too, than for subsequent babies.

What matters is that you offer your breasts to your baby frequently and flexibly as best you can from after the birth, with lots of skin-to-skin contact.

What do you feel when your milk comes in?

When your milk comes in, your breasts might start tingling and feeling uncomfortably tight and hot and full. You might notice you are leaking milk.

Researchers have shown that these are reliable signs of the milk coming in for most women, even though there's a lag of a day or so between when secretory activation actually kicks in, and when you feel it.

Sometimes when your baby suckles frequently and flexibly from birth you won't even feel signs of breast discomfort - your gradually increasing milk production keeps pace with your baby's increasing needs. But this will also depend on your underlying genetic milk production settings. Most women are biologically primed to breastfeed twins or multiples, with biological settings that initially generate much more milk than a single newborn needs. And yet others don't experience any breast changes with secretory activation despite normal production.

What will you notice in your baby as your milk comes in?

Your baby's need for milk over the first week of life increases in tandem with your increasingly abundant production of transitional milk. The most important and reliable signs that your milk supply is becoming plentiful are observed in your baby, who will have:

Five heavy wet nappies in a 24-hour period from the third or fourth day.
Stool colour change from black or dark green to the mustard colour of breast milk stools.
Two or more palmfuls of stool in the nappy over a 24-hour period. Often this may be three palmfuls or more. By this, I mean that you were to place the palm of your hand against the nappy, that area is covered with stool.
The soft 'k' sound your baby makes with a swallow occurs more frequently. This is a useful sign, though it may not be suck-swallow-suck-swallow and it may not be regular.

Each woman and her breastfeeding baby are unique, with diverse experiences of the milk coming in. Here are other things you might notice, though it is also possible you won't notice them at all.

Colostrum changes from a thicker yellower secretion to the greyish-whitish colour of milk (but don't feel you have to express to check this out! You can trust your body).
The sensation of letdowns. You can find out about your letdowns here.
Baby drowses to sleep or appears 'milk drunk' after a feed. This doesn't always happen. You can find out about burping or holding upright after breastfeeds here.

When do you need to worry that your milk hasn't come in?

From an evolutionary perspective, your baby has physiological mechanisms in place to thrive even when it takes five days for your transitional milk to become plentiful. In this time your baby doesn't need big volumes of milk. You can read about your newborn's tummy here.

Your newborn has stores of body fat for energy, and is prepared for a period of physiological dehydration after the birth, as the kidneys gear up into action. However, we do need to be sure that your baby is starting to pass urine and stool, and its important that you and your newborn check in with your health professionals regularly during these first days and weeks.

Your breast is never empty - production is gradually ramping up. As long as you are offering your breast frequently and flexibly, with abundant skin-to-skin contact, your baby receives small but powerful inoculations of colostrum.

To make sure that your milk comes in abundantly, so that your baby has the best chance of exclusively breastfeeding, try to make sure that you

Are offering frequent flexible feeds. This doesn't just waiting for baby to dial up before offering the breast, but offering (without placing any pressure on the baby) very frequently, especially in the first day, and in the first two weeks. The baby will soon let you know if he or she isn’t interested! You can find out about frequent flexible breastfeeds here.
Have baby in a stable fit and hold, with no breast tissue drag. You can find out about fit and hold starting here.

As health professionals we do start to pay attention if your milk hasn't come in by the end of the third day. Your baby may need daily assessment, since there are many factors in our society which disrupt what might otherwise be biologically normal processes over that first week after the birth.

You can find out about delayed onset of lactation here.

My own story

I have a powerful body memory of my milk coming in for the first time, even though it happened 35 years ago! I was alone in the night on a creaky hospital bed, severely sleep deprived after birthing my daughter, tossing restlessly. My breasts were hot and tight and hurting. A plastic mattress-protector crackled under the stiff white sheets and my perineum throbbed and burned. Where was my baby? This was 1990, and they'd taken her to the nursery.

As the long night hours passed, strange wet patches bloomed on the sheets, sticky against my skin. I realised only gradually that this is what they meant by the milk coming in. How strange and uncomfortable! How weird it was. ... How lonely.

I would wish for you the presence of someone who loves you, and I am glad that partners are encouraged to stay with new mothers more often these days. But plenty of us give birth without partners. I would wish for you much better information than I had about what was going on, too! (I was a doctor, but that didn't seem to help much ... )

Life is often much harder and much lonelier than we ever expect. So even if you are alone, remember that you are joined in your body's strange new experience with women all around the world and with women from the beginning of human time, whose milk came in even though they were alone - a wellspring of milk for the nurturance of their precious little baby. Your milk has come in so that you can nurture life into the next generation of human beings. An ancient river of women's milk is now flowing through your body. How extraordinary!

Recommended resources

What happens inside your breasts to make your milk come in

Frequent flexible breastfeeds make life easier, not harder

Your milk ejection reflex: what letdown feels like and how it works

What you need to know about baby weight gain in the first two weeks of life?

Busting myths about your letdown or milk ejection reflex

How small are newborn tummies really, and why do they need to suckle so much?

How can you tell if your baby is getting enough milk from direct breastfeeding?

Selected references

Warden AH, Sakalidis V, McEachran JL. Consecutive lactation, infant birth weight and sex do not associate with milk production and infant milk intake in breastfeeding women. Nutrients. 2025;17(6):1062;https://doi.org/1010.3390/nu17061062.