Why Is Baby Not Drinking Enough


It’s obvious when a bottle-fed baby is not drinking as much milk as expected. But does this mean she’s not drinking enough? Maybe ‘yes’. Maybe ‘no’. This article explains how to tell if your baby is underfeeding and the various reasons why babies don’t drink enough milk.

How to tell if baby is underfeeding 

Are you worried that your baby is not drinking enough because she’s not drinking as much as you have been told she needs? Or because her weight gain is low?

The fact that a baby doesn’t eat as much or gain as much as expected is not proof that she’s not eating enough. It could be that her milk needs have been overestimated or that expectations about her growth are unrealistic given her circumstances. 

The first step toward solving this puzzle is to identify if your baby is underfeeding. Underfeeding means a baby is not ingesting enough milk to meet her growth and energy needs.

So how can you tell if your baby is underfeeding? There are physical signs and behaviour that indicate if a baby’s nutritional needs are met or not.  These are listed in the table below.

Signs of a baby’s nutritional status 

Growth is not a reliable indicator of a baby’s current nutritional state.  A baby’s prior growth could be poor but the problem having caused this may be resolved.  So while a baby might be underweight she could still be well fed at present.  Or it could be that baby’s growth is perceived as being poor when in reality it’s not.  There are a number of reasons why a thriving baby’s weight gains can appear to be poor. (See Growth false alarms and Variations of normal growth.)

If you have now confirmed that your baby is not drinking enough milk to meet her nutritional needs, the next step is to identify the cause.

Reasons for underfeeding

There are a number of reasons why a baby might not drink enough to meet her needs; these include:

  1. Baby chooses to avoid feeding.
  2. Baby is too tired to feed effectively.
  3. Baby has poor appetite.
  4. Baby is prevented from effectively accessing the food (something is making it difficult for her to drink enough).
  5. Baby has impaired ability to suck.
  6. Baby is not offered enough milk (breastmilk or infant formula).

1.  Baby chooses to avoid feeding

Why would a hungry baby choose to avoid feeding? If she finds the experience of feeding to be unpleasant, stressful or painful she might. Reasons a baby may prefer to go hungry than to eat include:

  • Feeding aversion.
  • Sensory processing problem.

Feeding aversion

A feeding aversion is one of the most common reasons for physically well babies and children to reject feeds or meals and consume less than they need. An unresolved feeding aversion can cause poor growth 

Babies can become averse to one, two or all three feeding methods, i.e. breastfeeding, bottle-feeding or eating solids. Typically a baby who has developed a feeding aversion willingly eats only when ravenous, and then only a little. She’s tense and upset at feeding times. She might scream at the sight of the bottle, when placed into a feeding position, or at some point during the feed, for example after being burped. She stops sucking and turns away or arches her back in an upset manner. Some babies, who have become averse to feeding will feed better in a sleepy state because they’re then less aware that they’re feeding.

Because a feeding aversion means a baby tries to avoid eating and doesn’t willingly eat enough for healthy growth, parents understandably feel they have no option other than to continue pressure baby to eat. But this makes the situation worse. More often than not the reason babies and children don’t want to eat is because they’re repeatedly pressured to eat.   

Sensory processing disorder

Babies can develop an oral aversion due to a sensory processing disorder. Babies who have a sensory processing disorder perceive sensations differently to others and become upset by situations and things that don’t trouble most other babies. They may find a particular smell, taste or feel of certain foods or feel of the nipple of a feeding bottle and other objects in their mouth objectionable. Or they may be less aware or hypersensitive to the sensation of hunger.

Oral aversion is not the same as a feeding aversion. A baby may be mistakenly diagnosed as having an oral aversion when in reality she has a feeding aversion. It’s important to make the distinction between oral and feeding aversion because the treatment for each is very different.

In the case of an oral aversion, a baby typically objects to anything in her mouth including the nipple of a feeding bottle. Whereas in the case of a feeding aversion, baby is happy to have things in her mouth just so long as it’s not the nipple of a bottle (or breast or spoon or food in the case of these types of feeding aversions). 

While a feeding aversion is one of the most common reasons for feeding refusal, an oral aversion is one of the least likely causes. So it’s essential that a feeding aversion is ruled out before assuming an oral aversion is the cause.

2.  Baby is too tired to feed effectively

A baby could become too tired to feed effectively or too exhausted to wake for night feeds for the following reasons.

  • If her tired signs are overlooked.
  • If she has learn to rely on sleep associations that cannot be maintained.
  • If she is given sedative medications. 

Overlooking tired signs

Overlooking or mistaking baby’s tiredness cues as hunger or boredom means baby might not get the opportunity to sleep when tired and is then at risk of becoming distressed due overtiredness, which may then be mistakenly attributed to pain. (See Baby tired signs and How much sleep do babies need?)

Sleep association problem 

Babies often learn to rely on sleep associations (i.e. props and/or something the parent does) as a way to fall asleep. Learning to rely on sleep associations that cannot be maintained throughout baby’s entire sleep can result in broken sleep. Baby may wake prematurely from sleep still tired and cranky as a result of insufficient sleep. (See Sleep associations for more.)

Sedative medications

A baby could be too sleepy to feed due to receiving sedative medications prescribed to treat colic, such as antihistamines, antispasmodics or others. (See Colic medications for more.) 

3.  Baby has poor appetite

There’s nothing more effective than a hungry tummy to motivate a baby to want to eat. Without hunger a baby has little incentive to eat. The reasons a baby might have a poor appetite for milk feeds include:

  • Illness
  • Strict feeding schedules
  • Solids


Any illness can negatively effect a baby’s appetite. Loss of appetite can be one of the earliest signs of illness before other symptoms become apparent. Weight loss can occur depending on the severity and longevity of the illness. However, once baby has recovered her appetite will return and she may then experience catch-up growth.

Typically an ill baby will reject feeds in a passive manner compared to strongly oppositional refusal that occurs when a baby is averse to feeding.

Strict feeding schedules

While many babies thrive on a feeding schedule, not all do. Ignoring a baby’s hunger cues while trying to make her feed at predetermined times can result in underfeeding and poor growth.

You have probably experienced times when you felt pangs of hunger and may have been prevented from eating or chose to ignore these, perhaps because you were dieting. And then found the discomfort disappeared. This is because in the absence of food your body will convert glycogen stores and body fat into energy and so the desire to eat, though still present becomes less urgent. This would undoubtedly occur when babies are kept waiting too long for food when hungry.

Another problem with strict feeding schedules is that a ravenous baby can become distressed and disorganized, reject feeds or feed poorly. If she was also prevented from sleeping due to hunger this will add to her disorganized state.


Milk (breastmilk or infant formula) is the most important food for a baby during the first year of life. While solids are important to complement a baby’s diet, starting from 4 to 6 months of age, solids are a poor substitute for milk. Starting solids before the age of 4 months, or giving solids at the wrong time in relation to milk feeds can result in a baby not drinking enough milk when offered. (See Starting solids for more.) 

4.  Baby is not able to access food

A baby could be physically capable of feeding, have a healthy appetite, and be willing to feed, but she could be prevented from feeding effectively because of the following reasons.

  • Poor positioning.
  • Equipment problems.
  • Latch problems.

Poor positioning

Baby could be held in a position that makes it difficult for her to feed. For example, her neck could be twisted and her head is pointing to the side, or her head could be flexed or extended in a way that makes it difficult for her to suck or swallow. 

Equipment problems

A bottle-feed baby could experience difficulty feeding because of inappropriate or faulty feeding equipment. The hole at the end of the nipple might be blocked; or the nipple may be too short for her to get a proper seal and maintain suction; or the nipple could be too slow for her causing her to wear out before eating enough; or the nipple ring of a non-vented bottle may be screwed on too tightly slowing the flow rate or causing the nipple to collapse; or the venting system of a vented bottle or nipple might be faulty, also affecting flow rate.

Latch problems

A breastfeed baby could have a problem latching to the breast. For example her mother might have flat or inverted nipples, or her mother might not provide the support she needs to effectively latch. Or she may be held in a position that makes it difficult to latch or remain latched.

5.  Baby has impaired ability to suck

A tiny percentage of babies have physical impairments that affect their ability to suck. These fall into two categories.

  • Structural problems.
  • Functional problems. 

Structural problems

A structural problem means baby has a physical abnormality affecting her ability to feed effectively, for example cleft palate, tongue-tie, or underdeveloped sucking pads (the fat pads in baby’s cheeks, which is usually only problematic for scrawny newborns).

Functional problems 

Even through there may be no observable physical abnormality, baby might not be able to suck effectively due to a neurological impairment, an absence of sucking reflex, or due to nerve compression or damage occurring during birth.

Both structural and functional problems will be evident soon after baby’s birth. If your baby fed well and thrived after birth, you can probably rule out these problems.

6.  Baby is not offered enough

Not offering baby enough to eat is frequently believed to be the cause when a baby doesn’t gain as much weight as expected. While this is a common cause of poor growth in third world countries where food is scarce or expensive, it’s rarely the reason for babies in developed countries to underfeed or display poor growth. In general, parents in developed countries offer their babies as much as milk as their baby is willing to take. The problem is that baby is not taking enough either because she’s not willing to or because she’s prevented from doing so.

Health professionals often advise parents to make sure their baby drinks a minimum specified amount at each feed. However, to make sure a baby drinks the recommended amount might involve some form of pressure. Repeatedly pressuring a baby to feed against her will is likely to cause her to develop a feeding aversion, which in turn will cause her to underfeed. So what eventuates are repeated feeding battles that stress baby and parents.

If a baby is not eating enough, there is a reason. Pressuring or forcing a baby to feed or eat is NOT an effective solution. It’s likely to create greater problems. (See Consequences of baby growth mistakes for how feeding aversions and other feeding-related problem develop.)


The two most common reasons that a baby might be assumed to be underfeeding are because:

  1. Baby is not drinking as much as expected.
  2. Baby is not gaining as much weight as expected.

In many cases where parents worry that their baby is not eating enough, there’s nothing wrong with baby’s milk intake or growth. 

Baby is not drinking as much as expected

If your baby displays visible signs that indicate she’s getting enough (described in the table above) then the problem might lie with your expectations or baby’s healthcare professional’s expectations about how much milk she needs.

There are numerous reasons why a baby might drink more or less than parents and health professionals expect. See How much milk does a baby need? for these.

Baby is not gaining as much weight as expected

If your baby displays signs that indicate she’s well fed then it’s likely that what is perceived as poor growth is due to a false alarm, a variation of normal growth, or that the problem that caused her growth to falter has already been resolved.

Unrealistic expectations can occur as a result of mistakes made by health professionals when assessing a baby’s growth. 

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