What is oversupply of breastmilk?

Your milk supply will usually adjust to your baby’s needs after about 6 weeks of breastfeeding. Some people continue to make more milk than their baby needs, and this is known as ‘oversupply’ or ‘hyperlactation’.

Oversupply can make breastfeeding difficult for both you and your baby.

What are the causes of oversupply?

Oversupply of breastmilk that continues after the first 6 weeks or so can have many causes.

Your feeding patterns may cause the oversupply. This may happen if:

• you are feeding your baby on a set schedule rather than according to need
• you are expressing too much to build up a good supply of milk
• your baby wants to suck for comfort

Other causes of oversupply include:

• too much prolactin in your blood (hyperprolactinemia)
• a genetic predisposition

How breastmilk oversupply affects your baby

Your baby may be unsettled or distressed during and after feeding. It can be hard to know whether they are still hungry or are getting too much milk too fast.

If you have an oversupply, your baby may:

• choke and splutter at your breast due to the high rate of milk flow
• put on weight quickly
• have excessive wind, causing unsettled, colicky behaviour
• have a lot of urine (more than 10 wees a day)
• have diarrhoea with green, frothy poos and nappy rash

How breastmilk oversupply affects you

Oversupply can also cause problems for you.

You might:

• feel your breasts refill very quickly after feeding your baby
• have breasts that feel lumpy and tight
• leak breastmilk more than usual
• have an explosive milk-ejection reflex — this makes it difficult to feed in public, and can make the start of each feed hard for your baby

You could develop:

• blocked milk ducts
• mastitis
• breast abscesses

Oversupply can make breastfeeding a less pleasurable experience for you and your baby. This can cause some mothers to think about early weaning if oversupply is not diagnosed and managed well.

How is breastmilk oversupply diagnosed?

It’s important that you get an accurate diagnosis. This is because strategies to manage oversupply often aim to reduce your breastmilk supply.

It’s essential to see a healthcare professional, who can watch your baby breastfeed to diagnose oversupply. This could be a:

• lactation consultant
• breastfeeding counsellor
• doctor
• child health nurse

Oversupply can easily be confused with breast engorgement or a fast ‘let-down’ reflex.

How is breastmilk oversupply treated?

The aim of treatment for oversupply is to reduce your milk production. This is best done with support of a healthcare professional.

‘Block feeding’ is a method that can help reduce your milk supply in just a few days.

• Feed your baby from only one breast at each feed.
• Space feeds out — at least 2 ½ hours apart.
• At your next feed, change to your other breast.
• Continue this pattern for a few days.
• You might need to hand express a small amount from the unused breast to relieve pressure or discomfort. Don’t empty that breast — the leftover milk in the unused breast triggers the reduction in your milk production.

Block feeding ensures that one breast always contains leftover milk. This will trigger your breasts to reduce their milk production, and should gradually resolve oversupply of milk. How long it takes varies from person to person.

Block feeding will also help to reduce the amount of thinner foremilk your baby eats. As your baby gets to drink more of the creamy hindmilk, you’ll see your baby’s stools (poos) get thicker. This tells you that you are making progress.

If your milk supply does not respond to block feeding, talk to your doctor or other healthcare professional.

Resources and support

For help with the diagnosis and treatment of oversupply, contact a health professional, such as a lactation consultant, breastfeeding counsellor, or child health nurse.

The Australian Breastfeeding Association website has more tips about managing oversupply.