Assessing a low milk supply

How much milk am I making?

Mothers with a low milk supply need to know how much milk supplement to give to their babies. When the baby is healthy, the amount of supplement can be learned by watching the baby’s hunger signs. Some mothers benefit from knowing how much milk they are making. There are three ways to estimate this. One is by measuring the amount of breast milk they can express. Another is by measuring the amount of supplement the baby needs to grow normally. This can be subtracted from the expected amount of milk a baby needs to provide a rough idea of how much milk a mother is making. A third method is to compare the baby’s weight before and after breastfeeding for several days. The latter two will show how much milk the baby takes in but not necessarily how much milk the mother can make.

A) Reasons for measuring breast milk amounts

There are two reasons to measure milk: 

  1. To know how much milk a mother makes. 
  2. To know how much milk a baby takes in. 

Most breastfeeding mothers have a full milk supply. Their babies grow well and there is minimal benefit for them to know how much milk they make or how much milk a baby takes in.  

A small number of mothers have a low milk supply or have babies who do not grow well without milk supplements. The amount of milk available to the baby varies with the type of problems and how well the problems have been addressed. 

Mothers with healthy babies who breastfeed normally but have a low milk supply may simply supplement the baby following the baby's hunger signs

Other mothers may benefit from knowing how much milk they make or how much their babies take in. For example, a mother may: 

  • Be curious about her milk supply.
  • Need the information to help accept the need to supplement the baby with milk.
  • Have difficulty reading the baby’s hunger signs and need some guidelines for how much to supplement. 
  • Wish to know if a certain herb or medication is increasing her milk supply.
  • Along with her health-care providers, need to know how much milk is available to a baby who is premature or sick and growing poorly and how much milk that baby is able to take in.

B) Tools for measuring breast milk amounts

There are two types of tools for measuring breast milk amounts:  

  1. Measuring how much milk a mother makes:
    1. By expressing
  2. Measuring how much milk a baby takes in: 
    1. By comparing the amount of milk supplement needed to the expected amount a baby needs to grow well.
    2. By weighing the baby before breastfeeding and after (before-and-after weights).

The mother’s milk supply and the baby’s milk intake can be very different.

  • In a regular breastfeeding situation, the baby takes in about 70% of the available milk. 
  • If the baby is not breastfeeding well, the baby may take in significantly less of the available milk. 
  • If the milk supply is low, babies tend to take in more of the available milk. 

Each of these tools will indicate the minimum amount of milk that a mother is making.

Expressing is a direct measurement of milk supply. However, it too can be limited as some mothers cannot express well.

Measuring supplements and before-and-after weights are an indirect measurement of a mother’s milk supply as they are dependent on the baby’s ability to breastfeed normally and on how much milk the baby can or wants to take in. A mother may have much more milk in the breast but the baby is unable or unwilling to take it in which can happen if the baby:

C) Assessing milk supply by expressing

Mothers can express to see how much milk they are making.

Instead of breastfeeding, mothers express and measure the amounts. They should have milk ready for the baby’s replacement feed while they are expressing. Before proceeding, mothers must ensure that the baby will accept such feeds.

Some mothers cannot express well for a variety of reasons and will leave milk in the breast, causing them to underestimate how much milk they are making (Meier 2016).  

While expressing can assess how much milk a mother makes, it does not show how much milk the baby is taking in. 

Here, in order of preference, are three ways to use expression to estimate milk supply:

1) Hourly expressing for four hours
Several studies show that mothers can express with a breast pump to assess their milk supply (Kent 2018; Lai 2010; Roznowski 2019; Roznowski 2020).
This is done as follows:

  1. Starting after the baby has breastfed, mothers pump every hour for four hours:
    1. Using a double electric pump.
    2. With the suction strength set to the maximum comfortable level.
    3. Until the milk flow is reduced to infrequent drips (about 10 minutes). 
  2. Mothers keep track of how much they pump.
  3. The baby is given a replacement feed when hungry.
  4. Breastfeeding resumes after the fourth pumping and when the baby is hungry. 

The amount of milk obtained at the third and fourth pumping is roughly the amount made each hour. These two amounts can be added together and divided by 2 to average the amount. This amount is multiplied by 24 to see how much milk is made in one day.

For example, a mother may pump 17 millilitres at the third pumping and 23 ml at the fourth. The average of the two is 20 ml. This amount is multiplied by 24 to see how much milk is made in one day. In this example, the mother makes about 480 ml (16 oz) each day.
The first two pumps are necessary to empty the breast.  
2) Occasional expressing

Mothers may express at the occasional feed, done several times and at different times of the day, since the amount of milk in the breast can vary. This will give a very rough idea of how much milk may be present.

3) Extended expression
Mothers may choose to only express and not breastfeed for 12 to 24 hours. It is more accurate than occasional expressing but has more risks. 

Mothers who do not express well may have over-full breasts at the end of this period. They should quickly stop expressing and resume breastfeeding. 

The longer the baby is away from the breast, the higher the risk of the baby being reluctant to resume breastfeeding.  

D) Assessing milk supply by measuring milk supplement amounts

A mother’s milk supply can be assessed by knowing how much milk supplement a baby needs to grow well. This method can give a general idea of a mother’s milk supply. 

If a mother has a low milk supply, a healthy baby who is growing well and can latch and suck and breastfeed normally will regularly be hungry after breastfeeding on both breasts. The amount of milk supplement can be learned by watching the baby’s hunger signs after breastfeeding.

The amount of supplement can be subtracted from the expected amount of milk a baby needs for a rough idea of how much milk a mother is making. The more supplement the baby needs to be satisfied after breastfeeding, the lower the milk supply.  

For example, a 2-month old baby needs about 800 millilitres (27 U.S. fluid ounces) of milk each day. If the baby shows all of the signs of getting enough milk when supplemented with about 300 ml (10 oz), it is reasonable to assume that his mother is making about 500 ml (17 oz).

This estimate is only a rough one as different babies need different amounts of milk. The range is wide and varies with size and age and how fast the baby is growing.  

For example, one 2-month-old baby may need only 650 ml (22 oz) a day to grow well, but another of the same age may need 1,000 ml (34 oz).

E) Assessing milk supply using before-and-after feed weights

Mothers who are concerned about how much milk their babies are taking in may benefit from before-and-after weights for 24 hours.

Before-and-after weights are done by weighing the baby before and after a breastfeed on a sensitive scale and calculating the difference.

If the baby is growing normally and can latch and suck well, before-and-after weights can also show the minimum amount of milk a mother is making. It may be more accurate than measuring expressed amounts of milk (Johns 2013; Kent 2006).

Before-and-after weights can also be used to see how much milk a weak, premature or slow growing baby takes from the breast.

Before-and-after weights used to assess milk supply:

  • Have limitations.
  • Require a sensitive scale.
  • Require two or more days of weighing the baby before and after all feeds and then adding the numbers.
  • Require the baby to latch and suck effectively. This may not be possible if the baby is premature, a sleepy newborn, a sick baby or a baby with a latching problem.

Please see your health-care providers if you need help with this. A breastfeeding specialist may be especially helpful.


Johns HM, Forster DA, Amir LH, et al. Prevalence and outcomes of breast milk expressing in women with healthy term infants: a systematic review. BMC Pregnancy Childbirth. 2013 Nov 19;13:212
Kent JC, Gardner H, Lai CT, et al. Hourly Breast Expression to Estimate the Rate of Synthesis of Milk and Fat. Nutrients. 2018 Aug 22;10(9)
Kent JC, Mitoulas LR, Cregan MD, et al. Volume and frequency of breastfeedings and fat content of breast milk throughout the day. Pediatrics. 2006 Mar;117(3):e387-95
Lai CT, Hale TW, Simmer K, et al. Measuring milk synthesis in breastfeeding mothers. Breastfeed Med. 2010 Jun;5(3):103-7
Meier PP, Patel AL, Hoban R, et al. Which breast pump for which mother: an evidence-based approach to individualizing breast pump technology. J Perinatol. 2016 Jul;36(7):493-9
Roznowski D, Wagner E, Riddle S, et al. Comparison of Infant Test-Weighing and Hourly Breast Expression in Measuring Maternal Milk production (P11-041-19). Current Development in Nutrition. 2019;3(S1)

Roznowski DM, Wagner EA, Riddle SW, et al. Validity of a 3-Hour Breast Milk Expression Protocol in Estimating Current Maternal Milk Production Capacity and Infant Breast Milk Intake in Exclusively Breastfeeding Dyads [published online ahead of print, 2020 Jul 16]. Breastfeed Med. 2020;10.1089/bfm.2019.0182