Read time 9 minutes

Show References
sleeping baby

Of course you worry about your baby’s weight. So here we look at what to do if your baby who you breastfeed is only slowly or is not gaining weight.

Your baby will be weighed at birth and at particular stages during their first weeks and months (NHS Choices, 2017a). This is because weight gain can be an important indicator of how healthy and well they are.

Your baby will be weighed in the first two weeks to make sure they are regaining their birth weight.

After the first two weeks, your baby should be weighed:

  • once a month up to six months old
  • every two months from six to 12 months old
  • every three months over the age of one.

(NHS Choices, 2017a)

Your baby will usually only be weighed more often if you ask for it or if health professionals are concerned about their health or growth.

Baby weight gain

What to expect

In the first few days after birth, your baby will probably lose a little weight as they get rid of urine and meconium (NHS Choices, 2017a). Most babies have returned to their birth weight by three weeks old (NICE, 2017).

Babies shouldn’t lose more than 10% of their weight from when they were born (NICE, 2017). If your baby loses more than this or has not returned to it by three weeks old, a health professional will assess them (NICE, 2017).


An assessment will look for signs of illness, like dehydration. The health professional will ask for details about how your baby has been feeding. The health professional might also ask to look at your baby having a feed. That can help them give you some support with feeding (NICE, 2017).

You can also ask your midwife, health visitor or breastfeeding counsellor to observe you feeding your baby. They can check your positioning and whether your baby is taking in milk effectively (NHS Choices, 2017a). They can also help to see whether your baby is attached well at your breast and they can spot a tongue tie (NHS Choices, 2017a).

If health professionals are concerned about your baby’s weight loss, they will continue to support you. Your baby should be reweighed at suitable intervals depending on the level of concern. Your baby might then be referred to paediatric services if they are showing signs of illness, obvious weight loss or if they’re not responding to feeding support.

What can I do if my baby is not gaining weight?

If your baby hasn't regained their birth weight and you're breastfeeding, you might need to offer them more breastfeeds. It can take time to get the hang of breastfeeding but there is plenty of support available.

Find out from your local NCT branch what breastfeeding support services are available in your area. An NCT breastfeeding counsellor might be available locally to visit you at home. You can ask a breastfeeding counsellor about how to increase your baby’s breastmilk intake.

You might have a local drop-in breastfeeding support session too, where you can meet other mums and their babies. Peer support like this can be really beneficial.

How is my baby's weight recorded?

After your baby is two weeks old, they will have their weight recorded on a centile chart in their red book (Royal College of Paediatrics and Child Health, 2016). Centile charts track average weight and height gain for all babies whether they are fed breast or formula milk.

A baby on the 25th centile is heavier than 24% of babies the same age, and lighter than 74% of babies the same age. Most babies roughly follow the same line of growth on the chart as they get older, while others veer away from the line or find a ‘new’ line (NHS Choices, 2017a).

Causes for concern

There might be concern about your baby’s growth if:

  • there is a fall across one or more weight centile spaces, if their birth weight was below the ninth centile
  • there is a fall across two or more weight centile spaces, if their birth weight was between the ninth and 91st centiles
  • there is a fall across three or more weight centile spaces, if their birth weight was above the 91st centile
  • their current weight is below the second centile for age, whatever their birth weight.

(NICE, 2017)

If there is concern about your baby’s growth, a health professional might:

  • perform a clinical, developmental and social assessment
  • take a detailed feeding or eating history
  • observe feeding or meal times
  • check for urinary tract infections and coeliac disease, if the diet has included gluten-containing foods
  • perform further investigations as needed based on the clinical assessment.

(NICE, 2017)

When your baby is weighed, you’ll be keen to make sure it’s done accurately. Your baby should be naked each time. Check the weight reading yourself and how it’s written in your records as mistakes can happen.

What if my baby’s weight gain is slower than expected?

Most babies who gain weight more slowly than expected are healthy with no underlying illness or difficulty. They might just be naturally slow at gaining weight (NHS Choices, 2017a).

You and your health visitor can discuss your baby’s weight. If there is concern but no urgent medical recommendations, the first step is to try to increase your baby’s intake of milk. You can:

  • Try breastfeeding more often, day and night.
  • Offer at least both breasts at each feed. Try ‘switch nursing’, which is when you try to use each breast several times at each feed.
  • Try breast compression.
  • Keeping your baby close to you, skin-to-skin when possible as this usually helps your baby to feed more often. This might be something you can try intensively over a period of a few days, it’s sometimes called a ‘babymoon’.

(NHS Choices, 2016a)

What about giving my baby expressed breastmilk?

Expressing and offering expressed breastmilk in addition to direct breastfeeds is another possibility. If your baby is feeding well from the breast, extra direct breastfeeds are an easier option. The more your baby feeds at the breast, the more milk your body will produce.

What about donor milk?

Donor milk is breastmilk from other mothers. It might be available from a hospital-based milk bank. But mostly, milk banks give milk to vulnerable, pre-term or sick babies who are still under hospital care. Donor milk is also available through private milk donation schemes. 

What is a supplemental nursing system?

Some women whose baby has problems breastfeeding use a supplementary nursing system (SNS). This device allows a baby to receive extra milk at the breast, rather than top-ups by bottle.

It is a container of milk connected to a feeding tube at the breast. The baby breastfeeds as well as receiving extra milk from the supplementary nursing system. You can use expressed breastmilk, donor milk or formula-milk in this system.

Does my baby need formula?

Using formula might be medically necessary to help your baby grow if their weight is still a concern. This might be the case if extra breastfeeds are not making enough difference or you can’t get donor milk (NHS Choices, 2017b).

Feeding your baby with formula milk does not mean you have to stop breastfeeding if you don’t want to – you can do both. It also doesn’t mean the benefits of breastfeeding are wiped out (NHS Choices, 2017b).

If you still want to breastfeed, you can limit the amount of formula and you may be able to drop it once your baby’s weight is ok, if that’s what you prefer. Talk about this with a breastfeeding counsellor or a healthcare professional.

Should my baby have solid food?

Babies under six months don’t generally benefit from food other than breastmilk or formula milk. Solids might not increase a baby’s calorie intake and may even mean a baby takes less milk than before. So it may be an ineffective way to address low weight (NHS Choices, 2015).

This is something you can discuss with your health visitor or GP (NHS Choices, 2015).

Most babies who are slow to gain weight eventually catch up and most are healthy with no underlying illness or difficulties. Weight is only one aspect of your baby’s health and development (NHS Choices, 2017a). Trust your instincts and contact your GP if you are concerned about your baby, especially if you think they might be dehydrated, which can be serious for young babies.

This page was last reviewed in January 2018.

Further information

NCT supports all parents, however they feed their baby. If you have questions, concerns or need support, you can speak to a breastfeeding counsellor by calling our helpline on 0300 330 0700, whether you are exclusively breastfeeding or using formula milk. Breastfeeding counsellors have had extensive training, will listen without judging or criticising and will offer relevant information and suggestions.

Read our list of breastfeeding support contacts to help you get support if you need it.

Find out from your local NCT branch what breastfeeding support services are available locally.

If you have serious concerns about your baby or are worried they are getting dehydrated contact your GP or 111.

NHS Choices. (2015) Your baby’s first solid foods. Available from: [Accessed 1st January 2018]

NHS Choices. (2016a) Breastfeeding: is my baby getting enough milk? Available from:  [Accessed 1st January 2018]

NHS Choices. (2016b) Breastfeeding your premature baby. Available from:  [Accessed 1st January 2018]

NHS Choices. (2017a) Your baby’s weight and height. Available from:  [Accessed 1st January 2018]

NHS Choices. (2017b) How to combine breast and bottle feeding. Available from:  [Accessed 1st January 2018]

NICE. (2017) Guideline NG75: Faltering growth - recognition and management of faltering growth in children. Available from:  [Accessed 1st January 2018]

Royal College of Paediatrics and Child Health. (2016) ‘Early years - UK-WHO growth charts and resources’. Available from:  [Accessed 1st January 2018]

Further reading

Nursing Times. (2017) ‘NICE backs team-approach for faltering growth concerns’ Available from:  [Accessed 1st January 2018]

World Health Organisation. (WHO) (2006) ‘The WHO Child Growth Standards’ Available from:  [Accessed 1st January 2018]

Related articles

sleeping baby

Courses & workshops

In-person NCT New Baby course

Find out more

NCT Introducing Solid Foods workshop

Find out more

Baby & Child First Aid

Find out more
NCT Membership
Support NCT Charity by becoming a member
Excited couple holding pregnancy test
Sign up to our weekly Pregnancy & Baby Guide