Breast milk production: How supply and demand works

Did you know your breasts produce milk to meet your baby’s demand? Read on to discover the incredible facts about your breast milk supply over the first days, weeks and months.

Your body is able to produce breast milk for your baby’s needs at every stage of your breastfeeding journey. Understanding how your breast milk supply gets ‘switched on’, what happens to your milk when your baby breastfeeds, and why your supply is in tune with him as he grows, will all help you get breastfeeding off to a good start.

The first day: Your breast milk production at birth

Your baby should be ready to begin feeding from birth. The active trigger of him latching on and sucking rhythmically helps to ‘switch on’ your milk-producing cells and initiate the supply of your first breast milk, colostrum.¹ Try to feed him during his first hour if possible, and as soon as he shows interest in feeding after that, to help lay the foundations of a good future breast milk supply.²

The first few days: Your breast milk coming in

During this phase of breast milk production, your body is waiting for the levels of the pregnancy hormone progesterone to drop (which start to fall after you deliver the placenta), and milk-producing hormones, including prolactin, insulin and hydrocortisone, to kick into gear. The hormones will get you on track with starting to produce milk.³ Around day three after your baby’s birth, your breast milk ‘comes in’ and your breasts may start to feel noticeably firmer and fuller.¹

The first month: Building your breast milk supply

In the first weeks, your body is really responsive to milk removal as it’s learning how much breast milk to make. Your prolactin levels surge each time you remove milk from your breasts, ensuring they complete their development. This process also matures your milk’s composition – during this phase of breast milk production your body is making transitional milk in quantities that continue to build.^3,4

The first weeks with your baby are vital for establishing a good breast milk supply in the long term. The more frequently your baby breastfeeds, the more milk you’ll make, through a process of supply and demand. Each time milk is removed from your breasts, either by your baby feeding or by you expressing, they will make more.

Remember, it’s normal for babies to feed a lot – perhaps as much as every 45 minutes – and this doesn’t mean they’re not getting enough milk. The frequent feeding is helping build your supply, so feed your baby on demand, rather than to a schedule.

“It’s easy to believe that you’re not producing enough milk in those first few weeks, because your newborn is feeding all the time, but this is natural,” says Jo, mom of two, UK. “We’re conditioned to think a tiny baby will only want to feed every few hours but that’s not necessarily true.”

Don’t forget too that babies also breastfeed for comfort. Breastfeeding makes your baby feel calm and contented as he adjusts to life outside the womb, as well as helping the two of you to bond.

Protecting your breast milk production in the first month

If you follow your baby’s lead and let him breastfeed as often as he wants, for as long as he wants, your breast milk production should follow.⁵

Some moms try to increase the gap between feeds to give their breasts more time to make milk, but this is not a good idea, as it can slow your milk production.²

If you can’t breastfeed your baby directly for the first two weeks, you can express to build and maintain your breast milk supply through this crucial period and beyond.

Did you know giving your baby extra bottles of formula unnecessarily can actually reduce your breast milk supply? It means your breasts aren’t getting the message to increase breast milk production, because milk isn’t being removed. Also, if your baby sleeps for longer after a bottle he might miss the next time he naturally would have breastfed.

This is sometimes known as the ‘top-up trap’. After three or four days of top-up formula feeds and less milk removal, the breasts get the message that weaning has started. In response, they reduce the amount of milk they produce. As a result, the baby becomes hungrier again, so another top-up formula feed often has to be given. And so the cycle continues… culminating in actual low breast milk supply and a baby who is now mostly formula-feeding. 

Your breast milk production beyond six weeks

After the first month, the prolactin surges after feeding start to decline, your milk is mature and your body has become really efficient at producing as much milk as your baby needs. In fact, your breasts start working as if they were on autopilot.⁴ You may also notice that your breasts feel softer and stop any leaking around this time.

At this point it’s common to worry about ‘losing your milk’. But it’s actually a sign that your breast milk production has settled down and is now in balance with your baby’s needs. Remarkably, although he’s growing all the time, he’ll only take about the same amount of milk at six weeks as he will do up to when he’s six months. You may find your baby feeds for longer periods, but less frequently. On the other hand, there may be days when he feeds a bit less than usual – a baby’s appetite can fluctuate, just like an adult's!

From now on, you produce milk on a supply and demand basis only. So, the more your baby drinks (or you express), the more you’ll make.

But how does this actually work? It’s thought to be because of something in your milk called FIL (feedback inhibitor of lactation) that controls milk production. The more milk your breast contains,² the more FIL there is – so a full breast makes less milk than one that is almost empty.

Is your breast milk supply normal?

While it’s common for moms to worry about breast milk production and how to increase their milk supply, when babies are healthy and growing well problems are surprisingly rare.

“I was worried that my newborn wasn’t getting enough breast milk as she only fed for short periods, and always from one breast at a time, although I offered her both,” says Marjorie, mom of two, UK. “But when I used a breast pump to express milk, I was surprised and reassured by how much I was producing. I just had to keep feeding her little and often.”

Do bear in mind though that not all moms respond quickly to a breast pump. You could also try hand expressing and feeling whether your breasts are changing from full to empty too.

If you’re concerned about your breast milk production, read our advice on how to tell if you have a low milk supply or too much milk.