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Ferrous fumarate

Ferrous fumarate is a medicine used to treat and prevent iron deficiency anaemia.

It comes as capsules or as a liquid that you swallow.

You can get it on prescription and buy it from pharmacies.

Ferrous fumarate may also be known by the brand name Galfer.

Get emergency help

You may need emergency help if you or your child:

  • have a serious allergic reaction
  • take too much ferrous fumarate

Both situations can be life threatening.

Serious allergic reaction

A serious allergic reaction to ferrous fumarate is rare. But you will need to go to an emergency department (ED) if you have symptoms.

Emergency action required: Call 999 or 112 or go to an ED immediately if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

These are warning signs of a serious allergic reaction (anaphylaxis).

If you take too much

Taking too much ferrous fumarate can cause vomiting, stomach pain or diarrhoea.

In serious cases you may vomit blood, bleed from your bottom, have a seizure or fit, or become unconscious.

Emergency action required: Call 999 or 112 or go to an emergency department (ED) immediately if you or your child:

  • takes too much ferrous fumarate

If you go to an ED do not drive yourself. Get someone else to drive you, or call an ambulance.

Take the ferrous fumarate packet or the leaflet inside it with you, and any remaining medicine.

When you start taking ferrous fumarate

You might feel better after taking ferrous fumarate for a week, but it may take up to 4 weeks to take full effect. If you still feel unwell after 4 weeks, talk to your GP or pharmacist.

You probably will not feel any different if you’re taking ferrous fumarate to prevent anaemia, but that does not mean it is not working.

You may experience these common side effects:

  • feeling or being sick
  • diarrhoea
  • constipation
  • a change in colour of your poo

Eating and drinking

Take ferrous fumarate 30 minutes before eating, or 2 hours after eating. If it upsets your stomach, you can take it with or just after food.

Try to wait 2 hours between taking ferrous fumarate and eating or drinking any of the following: 

  • tea and coffee
  • milk and dairy products – such as yogurt and cheese
  • eggs
  • soybean products – such as soya beans and soya milk

This will help your body take in the iron.

You can drink alcohol while you are taking ferrous fumarate.

Check if you can take ferrous fumarate

You can usually take ferrous fumarate if you’re aged 18 and over.


Keep ferrous fumarate out of the reach of children. An overdose of iron can cause death.

Ferrous fumarate is not harmful if it’s been prescribed for your child and you follow your GP’s instructions, or the instructions on the packet.

If you buy this medicine from a pharmacy, tell the pharmacist before starting ferrous fumarate if you:

  • have had an allergic reaction to ferrous fumarate or any other medicine in the past
  • have a different type of anaemia that is not caused by low levels of iron
  • have any other conditions that affect your iron levels, such as haemochromatosis or haemosiderosis
  • have a condition that affects your red blood cells, such as sickle cell anaemia or thalassaemia
  • have a stomach ulcer, or other stomach or bowel problems such as inflammatory bowel disease
  • are receiving repeated blood transfusions
  • have noticed blood in your pee

Pregnant or breastfeeding

Tell your GP if you're trying to get pregnant, already pregnant or breastfeeding.

It's usually safe to take ferrous fumarate during pregnancy or when breastfeeding.

Some of the medicine may pass into your breast milk in small amounts but it’s unlikely to harm your baby.

It’s common to become constipated or develop piles (haemorrhoids) if you’re pregnant and taking iron supplements. If this happens to you, talk to your GP. 

How and when to take ferrous fumarate

Follow your GP’s instructions about how and when to take ferrous fumarate. 

Follow the instructions that come with the packet if you buy it from a pharmacy.

Your GP or pharmacist may recommend taking ferrous fumarate with orange juice or a vitamin C supplement. This is to help your body absorb the iron.

Do not use a kitchen teaspoon to measure the liquid because you will not get the right amount. The medicine will come with a plastic syringe or spoon to help you measure the right dose. If you do not have a plastic syringe or spoon, ask your pharmacist for one.

If you forget to take it

Do not take a double dose to make up for a forgotten dose.

If you usually take it:

  • once a day – take it as soon as you remember. But if it's less than 12 hours until your next dose, skip the missed dose.
  • 2 times a day – if you remember within 4 hours of your missed dose, take it as soon as you remember. If you remember more than 4 hours after your missed dose, skip the missed dose and then take your next dose as normal
  • 3 times a day – skip the missed dose and take your next dose as normal

Side effects of ferrous fumarate

Many people have no side effects or only minor ones.

Talk to your GP, a pharmacist or nurse if these side effects bother you or do not go away:

  • feeling or being sick (nausea or vomiting), stomach discomfort or heartburn
  • loss of appetite
  • constipation
  • diarrhoea
  • dark or black poo
  • black stained teeth (from the liquid only)

See the patient information leaflet that comes with your medicine for a full list of side effects.

Non-urgent advice: Find your patient information leaflet

Your patient information leaflet is the leaflet that comes with your medicine. You can find a digital version of the leaflet online.

Report side effects

You can report any suspected side effects to the the Health Products Regulatory Authority (HPRA): report an issue -

Taking ferrous fumarate with other medicines

Some medicines interfere with the way ferrous fumarate works. If you’re on any other medicines or supplements, check with your GP, a pharmacist or nurse before you start taking ferrous fumarate. 

Try to leave a gap between taking the other medicine and ferrous fumarate. Ask your GP, a pharmacist or nurse for advice on how long the gap should be.

Fact check

This content was fact checked by a pharmacist, a GP, the National Medication Safety Programme (Safermeds) and the Health Products Regulatory Authority (HPRA).

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 24 September 2021
Next review due: 24 September 2024