Iron (Ferrous Sulphate) For Premature & Small Babies

Iron (Ferrous Sulphate) For Premature & Small Babies

Iron is important for brain development and making new red blood cells to prevent a low red blood cell count.


Key points about iron (ferrous sulphate) for premature and small babies

  • iron is vital for body function
  • it is especially important for brain development and making new red blood cells to prevent a low red blood cell count (anaemia)

A mother giving iron to her baby and a bottle of iron

What is iron for?

Iron is vital for body function. It is especially important for brain development and making new red blood cells to prevent a low red blood cell count (anaemia). In the last few months of pregnancy, your baby stores iron in their body to use after they are born. Well grown, full-term babies have stored enough iron to use until they are 6 months old and do not usually need iron medicine.

Why do some babies need extra iron?

Some babies do not have as much iron stored in their body. What iron they do have is used up as they grow. They need extra iron to prevent iron deficiency.

These babies include:

  • premature babies (babies who were born early - before 37 weeks)
  • those who are small (weighed less than 2.5 kg at birth)

How much iron will my baby need?

Your baby's iron dose will depend on their weight. Your family doctor can increase the dose with each new prescription as your baby gains weight. Most babies have a dose of between 0.4 and 0.6ml per kg per day. In most cases, babies have iron once a day.

When should my baby start taking iron medicine?

Very premature babies

If your baby was very premature, they will start having iron medicine when they are in the hospital. 

Babies born under 37 weeks or under 2.5 kg

You may need to start giving iron medicine after your baby goes home if:

  • your baby was born under 37 weeks
  • your baby was born after 37 weeks but weighed less than 2.5 kg at birth

Your healthcare team will tell you when to start giving your baby iron medicine. This is usually between 2 to 4 weeks after birth. 

When should my baby stop taking iron medicine?

Keep giving iron each day until your child's first birthday or your doctor asks you to stop.

Your doctor will need to increase the dose as your baby grows.

How do I give iron to my baby?

You can use a syringe or a medicine teat to give iron to your baby. It absorbs better on an empty stomach so try to give it before a feed. You can give the iron with breastmilk to make it taste better. But, give the iron between meals once your baby is established on solids. 

What if my baby vomits?

If your baby vomits less than 30 minutes after giving the iron, give the same dose again If it is more than 30 minutes, do not give another dose until it is next due.

How will the iron affect my baby?

Babies react to the taste, but this does not mean it is a problem. Your baby's poo (bowel motions) may become a darker colour, but this is harmless. The poo can become a little firmer and some babies become constipated when they first start taking iron, but this usually settles. If your baby vomits or spits up this may also be a darker colour.

Where should I store the iron?

Keep the medicine in its container and out of reach of children. It is a good idea to store it in a cupboard, away from heat and direct sunlight. You do not need to keep it in the fridge. The syrup is normally colourless, but if the colour varies from bluish green to gold this is OK.


The content on this page has been developed and approved by the Clinical Reference Group of the Newborn Clinical Network, Paediatric Society New Zealand.

This page last reviewed 24 September 2021.

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