Patient Information

Human milk fortifier for your baby


This information leaflet is for parents of infants who have been recommended to use human milk fortifier by the neonatal team.

Milk fortifier

What is human milk fortifier?

Human milk fortifier (or breast milk fortifier) is a powder added to breast milk to boost a baby’s nutrition. Some parents think of fortifier as a ‘protein shake’ for their baby.

The main nutrients in the fortifier powder are:

  • some proteins (for tissue and brain growth)
  • some carbohydrates (for energy and growth)
  • calcium
  • phosphate (for bone strength)
  • some micronutrients (vitamins, minerals and salts) which are needed, for example for bone health.

These nutrients are essential for your premature baby to grow well.

Which babies are offered human milk fortifier?

We usually offer human milk fortifier to low weight premature babies or premature babies who are not gaining as much weight as expected. This may be due to medical complications such as chronic lung disease, cardiac (heart) problems or immature kidneys. Using fortifier is part of routine care in the neonatal unit.

Why have you suggested breast milk fortifier to me?

Premature babies have greater nutritional needs than term babies. This is because they have missed out on nutrients they would have received through your placenta during the last term of pregnancy.

Breast milk alone does not have enough protein and nutrients to meet the extra nutritional needs of a premature baby. The fortifier covers this gap. It means premature babies can receive full nutrition in a volume of breast milk that is manageable for them.

We have not suggested breast milk fortifier because your milk is ‘not good enough’.
Giving your baby fortifier does not mean your baby will stop breastfeeding.
Breast milk is the absolute best food for your baby. It is easily digested and helps your baby’s immune system to fight infections, particularly a serious bowel infection called NEC.

How long will my baby need fortifier?

We do not use fortifier long term.

We generally stop fortifier around the baby’s estimated due date. Your dietitian will monitor your baby’s growth and will offer guidance. 

Are there side effects of using fortifier?

Neonatal units have used fortifier for the past 20 years. Babies usually tolerate it well.

On rare occasions, a baby may vomit, pass more stools (poo) or get more constipated.  (This often happens even without fortifier, as the gut of premature babies is still immature.)

There is no evidence linking fortifier to an increased risk of the bowel infection known as NEC.

There is no evidence linking fortifier to the risk of cow’s milk allergy (sometimes called ‘intolerance’). Fortifier powder is made of dried cow’s milk and the milk proteins are already broken down as an extra safety factor.

Your neonatal team will monitor your baby closely when fortifier is introduced. This is to ensure your baby tolerates the fortifier.

How much fortifier will you suggest for my baby?

Paediatrics logo

To start with, we will weigh the fortifier exactly for each feed. We will adjust it to the volumes of breast milk taken by your baby.

As your baby gets closer to discharge and breastfeeding becomes more established, we will adjust how much fortifier to give and how to give it.

We may use one or two sachets added to a tiny amount of your expressed breast milk and give this to your baby as concentrate, just before or after a breastfeed. This routine will make it easier for you to give fortifier when you take your baby home.

We will also discuss with you the different ways to give the fortifier, for example via a syringe or with a bottle or through a feeding tube.

More information

bliss logo
Information from Bliss for babies born premature or sick

Image by shirkin_son at Freepik.

Human milk fortifier for your baby - Kingston Hospital Download PDF


Kingston Hospital Neonatal Unit Reception, Monday to Friday 9 am to 4 pm 020 8934 2421

Translate Please speak to a member of staff before or during your visit to the hospital if you require translation.
Accessibility Please contact the Patient Experience Team on 020 8934 3850 if you need this information in a different format.
For information accessibility please visit Kingston Hospital AccessAble www.accessable.co.uk/kingston-hospital-nhs-foundation-trust
Support services

Visit the hospital website, ask a member of staff, or ring us for details.


Switchboard 020 8546 7711

  • ‘Find Us’ page for maps, transport, registering a blue badge, disabled access
  • Information, advice and support for patients and relatives (PALS) 020 8934 3993
  • Pastoral and Spiritual Support 020 8546 7711
  • Learning Disability Liaison Team 020 8934 6895
Print - Standard Size Print - Large Size


Please speak to a member of staff before or during your visit to the hospital if you require translation support to access Patient Information. Please ring the phone number on your appointment letter, if you have one.

Request More Information


Please contact the Patient Experience Team on 020 893 3850 if you need this information in a different format.
For detailed information on accessibility at Kingston Hospital visit Kingston Hospital AccessAble (https://www.accessable.co.uk/kingston-hospital-nhs-foundation-trust).

Tell us how we are doing we'd love to have your opinion