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Lactose overload in babies

By Joy Anderson BSc(Nutrition), PostgradDipDiet, IBCLC, ABA Breastfeeding Counsellor 

It is common for a mother to make more milk than her baby needs in the early weeks before her supply adjusts to match her baby’s needs.  During this phase, most babies remain fairly settled and have normal numbers of wet and dirty nappies. However, sometimes this is not the case. This article describes how to tell if your baby is taking too much milk, too fast, and what you can do to help resolve the situation quickly.

What is lactose overload?

Lactose overload is often seen in babies consuming large amounts of breastmilk, that is when their mothers have an oversupply. It typically occurs in babies under 3 months old and can usually be easily fixed. A large-volume, low-fat feed goes through the baby so quickly that not all the lactose is digested (more fat would help slow it down). The lactose reaching the lower bowel draws extra water into the bowel and is fermented by the bacteria there, producing gas and acid stools. The acid stools often cause a nappy rash. Gas and fluid build-up cause tummy pain and the baby 'acts hungry' (wants to suck, is unsettled, draws up his legs, screams). Sucking is the best comfort he knows and also helps move the gas along the bowel. This tends to ease the pain temporarily and may result in wind and stool being passed. Since the baby looks like he wants to suck at the breast, his mother, logically, feeds him again. Sometimes it is the only way to comfort him. Unfortunately, another large feed on top of the earlier one hurries the system further and results in more gas and fluid accumulation. The milk seems almost literally to 'go in one end and out the other'.

How do you know if your baby has lactose overload?

Lactose overload can result in an unsettled baby with adequate to large weight gains. The baby usually passes urine more than 10 times a day and has many (often explosive) bowel motions in 24 hours. They may have green, frothy poos that resemble those of a baby with lactose intolerance. Ironically, a mother may think that she has a low milk supply because her baby always seems to be hungry. The nappies can be the biggest clue to what's happening. What comes out the bottom must have gone in the top!

It is important to note that green-coloured poos can be normal since the colour of breastfed babies' poos can be anything from orange to yellow to green. Green often just means that the gut contents have gone through quickly. On the other hand, scant dark-green-coloured poos can mean insufficient milk intake.
Also, note that some mothers appear to have a very fast let-down, so that their babies have problems coping with the milk flow. They may come off the breast coughing and may appear to be choking on the milk. While this may be associated with an oversupply of breastmilk, it does not necessarily mean that. It is important to know that there needs to be other signs that there is an oversupply before taking steps to address this issue. These include those mentioned above: many wet and dirty nappies and good-to-high weight gain.

What can be done about lactose overload?

Many mothers whose babies have had this problem have found it helpful to block-feed. The aim of block-feeding is to slow the rate at which milk goes through the baby by feeding one breast per feed. This is usually only necessary for a few days. To block-feed, set a 4-hour time period (this may be adjusted according to the severity of the oversupply) and every time your baby wants to feed during this period, use the same breast. Then use the other breast for the next 4 hours, etc. Each time your baby returns to the already used breast, he gets a lower-volume, higher-fat feed that helps slow the system down. While block-feeding, check that the unused breast does not get overfull. Check for potential blocked ducts and if you find a lump, feed or express it out. You don’t want to end up with mastitis! In most cases you should see a difference in about 3-4 days. Your baby may settle better, cry less and the numbers of nappies may have slowed down a little.

As soon as your baby's symptoms are relieved, go back to normal breastfeeding. Check the numbers of nappies. Normal numbers for a young baby are 5 heavy single-use (or 6 very-wet, cloth) nappies, and at least 3 soiled nappies per 24 hours. Make sure you don’t continue the changed feeding pattern so long that the numbers drop below these. Otherwise you may not have enough milk.

In most cases, a mother should be able to resolve this problem in only a few days. Where it is severe and/or long-lasting, it is worth trying to work out why there is an oversupply of breastmilk.

  • Is the mother timing feeds and switching sides after a set number of minutes?
  • Has something caused the baby to be unusually unsettled, resulting in frequent comfort sucking and an oversupply?
  • Is secondary lactose intolerance adding to the overload situation?
  • Sometimes a mother who is worried about having a low supply overcompensates by offering more feeds than the baby needs and overstimulates her supply.
  • Occasionally, mothers take medication or herbal preparations reputed to increase milk supply, ‘just in case’, if they are worried about not making enough milk, or they think their baby’s unsettledness is caused by hunger.
  • Perhaps the baby has been unwell, or is suffering discomfort from a difficult birth, and seeks comfort in more frequent feeds than he needs to satisfy hunger.
  • Some mothers just have a tendency to oversupply. There is a normal variation in this as in everything else about our bodies. In days gone by, these may have been the mothers who could have made a living as wet nurses!

Specific ways to help with each of these is beyond the scope of this article. However, individual situations can be discussed with an Australian Breastfeeding Association counsellor, an International Board Certified Lactation Consultant (IBCLC), a dietitian with an interest in infant feeding or other health professional. The Association's booklet 'Breastfeeding: and your supply' has tips for helping oversupply problems. ‘Breastfeeding: and crying babies’ has lots of suggestions for soothing unsettled babies.


Brodribb W (ed), 2012, Breastfeeding Management in Australia. 4th edn. Australian Breastfeeding Association, Melbourne.

Woolridge M, Fisher C 1988, Colic, 'overfeeding' and symptoms of lactose malabsorption in the breast-fed baby: a possible artifact of feed management? Lancet (ii): 382-384.

© Australian Breastfeeding Association Reviewed April 2021



Last reviewed: 
Apr 2021