Breast milk supply: how it works and how to increase it

Breast milk supply works on supply and demand. The Australian Breastfeeding Association's guide to increasing supply puts it simply: the more milk that's removed from your breasts, the more milk you make. That's why the most effective way to make more milk is to breastfeed more often, and why regular formula top-ups or long gaps between feeds can lower it.

Most supply worries turn out to be normal baby behaviour or normal changes in your breasts. This guide explains how supply works, what genuinely causes low supply, how to increase it, and what oversupply looks like. To check whether your baby is getting enough right now, see is my baby getting enough milk?.

How does breast milk supply work?

Your breasts make milk in response to milk being removed. Each time your baby feeds well, or you express, your body gets the signal to keep making milk. The Academy of Breastfeeding Medicine's 2022 mastitis protocol describes the same feedback loop: more milk removal increases production.

A few things follow from this:

• Frequent feeds build supply. The Australian Breastfeeding Association says most young babies feed 8 to 14 times in 24 hours, and feeds can last anywhere from 5 to 10 minutes to 30 minutes or more.
• You don't need to wait for your breasts to "fill up". Milk removal drives supply, so feeding again soon after a feed is fine.
• Breast size doesn't decide how much milk you can make.
• Night feeds count. Milk-making hormones peak at night, which is why the Australian Breastfeeding Association suggests waking your baby for a missed night feed if you're trying to boost supply.
• Supply settles over the first weeks. As your body learns how much your baby needs, your breasts usually feel softer and less full. This is normal.

You don't need to "empty" a breast. Aim for a well-fed, satisfied baby, not a breast that feels drained.

Is my milk supply actually low?

Often it isn't. The Australian Breastfeeding Association's page on low supply lists common experiences that are mistaken for low supply:

The best check is your baby. The NHS signs your baby is getting enough milk include at least 6 heavy wet nappies a day from day 5, regular soft yellow poos and steady weight gain. The Australian Breastfeeding Association uses at least 5 heavily wet disposable or 6 soaking cloth nappies. If nappies and growth are on track, your supply is very likely meeting your baby's needs. If you're also seeing lots of wet and dirty nappies with green, frothy or explosive poos, think about oversupply instead (below).

What causes low milk supply?

When supply really is low, there's usually a reason, and many are fixable. The Australian Breastfeeding Association's article on why supply can be low and its guide to increasing supply describe three groups.

How feeds are managed

• Scheduled feeds. Feeding strictly every 3 to 4 hours, and settling a hungry baby with patting, rocking or a dummy instead of a feed, can reduce supply.
• Regular formula top-ups. Your baby is less hungry for the breast, so less milk is removed.
• Fewer breastfeeds for any reason, including a baby who has started sleeping longer stretches.

Your baby

• Poor attachment. A baby sucking mostly on the nipple removes less milk. Painful feeding is a clue; see latch and positioning.
• Tongue-tie, which can stop a baby removing milk well.
• Illness, or a medical condition that makes it harder for your baby to suck well.

Your body

• Thyroid problems, such as an underactive thyroid, which can reduce supply. Treatment can help.
• PCOS (polycystic ovary syndrome), which may reduce supply.
• A retained piece of placenta or heavy blood loss after birth, which can delay milk coming in.
• Insufficient glandular tissue, where milk-making tissue didn't fully develop. La Leche League says possible signs include little breast growth in pregnancy and widely spaced or tube-shaped breasts, though they aren't always obvious.
• Being very unwell yourself.

Several of these need a doctor's assessment. Many mothers with a medical cause still breastfeed partly, sometimes alongside donor milk or formula — see combination feeding.

How can I increase my breast milk supply?

These steps come from the Australian Breastfeeding Association's guide to increasing supply. Most people notice a difference within a few days.

1. Offer more breastfeeds. This is the simplest and most effective step. Follow early hunger cues rather than the clock, and add quick extra feeds between the usual ones.
2. Use the breast for comfort. During fussy periods, offer a feed instead of a dummy.
3. Don't skip night feeds. If your baby sleeps through a feed, you can wake them.
4. Switch sides. Let your baby finish the first side or switch when sucking slows — even several times in one feed — to trigger another let-down.
5. Try breast compressions. When sucking slows, gently press your breast (away from the nipple) to help milk flow.
6. Check the latch. A well-attached baby removes milk more easily.
7. Help your milk flow. Relaxing, slow breathing and warmth on the breast before feeding can help.
8. Cut back on top-ups gradually, with support. Replace them with extra breastfeeds while someone keeps an eye on your baby's nappies and weight.
9. Add expressing if needed. Short sessions of 5 to 10 minutes, repeated several times over an hour or two, then finishing with hand expression, can add extra stimulation. Expressing one breast while your baby feeds from the other saves time.

If you're thinking about a medicine or herbal product to increase supply, talk to your doctor first. For pump fit and routines, see pumping basics.

What is oversupply, and how is it managed?

In the early weeks, extra milk is normal and usually settles by about 6 weeks. The Australian Breastfeeding Association's oversupply page suggests oversupply after that when you notice several of these:

• breasts that refill quickly after a feed and feel lumpy or tight
• a baby who is often satisfied with one breast
• faster weight gain than expected
• more than 6 heavy wet nappies in 24 hours
• poos at nearly every feed, sometimes green, frothy or explosive
• a baby who gulps or gags with the flow.

Wind, fussiness and crying are common in many babies, so on their own they aren't clear signs.

To bring supply down gently, it suggests offering one breast per feed (and the same breast again if your baby wants more soon), expressing only enough to relieve discomfort, and comforting your baby in other ways between feeds. The ABM protocol warns that "pumping to empty" keeps supply too high and raises the risk of breast inflammation. Watch for tender, firm or red areas, and see mastitis if they appear. Talk to a breastfeeding counsellor before trying stricter methods such as block feeding.

When should you get help with your milk supply?

Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) now if your baby has had no wet nappy for 12 hours, is hard to wake, floppy or too sleepy to feed, or has blue, grey or mottled skin — these are among the emergency signs in the NHS guide to whether your baby is seriously ill.

See your GP, midwife or child-health nurse today if your baby is refusing feeds, has fewer wet nappies than expected, dark or strong-smelling wee, or seems hungry after most feeds.

Get feeding support soon — a lactation consultant, child-health nurse or a breastfeeding helpline (the Australian Breastfeeding Association on 1800 686 268 in Australia, the National Breastfeeding Helpline on 0300 100 0212 in the UK) — if:

• your baby isn't regaining birth weight or gains are slow
• you've tried feeding more often for a few days and nothing has changed
• feeding hurts, or you suspect tongue-tie
• you've had breast surgery, a thyroid condition, PCOS, heavy bleeding after birth, or little breast change in pregnancy
• you're relying on top-ups and want to reduce them.

What's useful to note

For two or three days, note feeds, wet and dirty nappies, any top-ups (with amounts) and any expressing. Bring it with your baby's weights; it shows a supporter much more than any single pumping session.