1. About ferrous fumarate
Ferrous fumarate is a medicine used to treat and prevent iron deficiency anaemia.
Iron helps the body to make healthy red blood cells which carry oxygen around the body. Some things such as blood loss, pregnancy or too little iron in your diet can make your iron supply drop too low, leading to anaemia.
Ferrous fumarate comes as tablets, capsules or as a liquid that you swallow.
It's available on prescription and to buy from pharmacies.
2. Key facts
- Ferrous fumarate works best when taken on an empty stomach.
- Most people feel better after taking ferrous fumarate for 1 week, but it may take up to 4 weeks to take full effect.
- Common side effects include feeling or being sick, and diarrhoea.
- Ferrous fumarate may also be called by the brand names Fersamal and Galfer.
3. Who can and cannot take ferrous fumarate
Most adults can take ferrous fumarate under the advice of a doctor or pharmacist.
Only give ferrous fumarate to a child if it has been recommended by a doctor.
Ferrous fumarate may not be suitable for everyone.
To make sure it's safe for you, tell your doctor or 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
4. How and when to take it
If you or your child are prescribed ferrous fumarate, follow your doctor's instructions about how and when to take it.
If you buy ferrous fumarate from a pharmacy, follow the instructions that come with the packet.
Ferrous fumarate tablets comes in 2 strengths – 210mg and 322mg.
Ferrous fumarate capsules are 305mg.
Liquid ferrous fumarate contains 140mg of ferrous fumarate in each 5ml spoonful (140mg/5ml).
The liquid may be easier for children and people who find it difficult to swallow tablets or capsules.
How much will I take?
The dose of ferrous fumarate depends on why you're taking it and whether you have tablets, capsules or liquid.
To treat anaemia
The usual dose of ferrous fumarate for adults and children over 12 years old is:
- 210mg tablets – 1 tablet, taken 2 to 3 times a day
- 322mg tablets – 1 tablet, taken 1 or 2 times a day
- 305mg capsules – 1 capsule, taken 2 times a day
- liquid (140mg/5ml) – two 5ml spoonfuls, taken 2 times a day
For children under the age of 12, a doctor will use your child's age or weight to work out the right dose.
To prevent anaemia
The usual dose of ferrous fumarate for adults and children over 12 years old is:
- 210mg tablets – 1 tablet, taken 1 or 2 times a day
- 322mg tablets – 1 tablet, taken once a day
- 305mg capsules – 1 capsule, taken once a day
- liquid – one 5ml spoonful, taken 2 times a day, or two 5ml spoonfuls taken once a day
For children under the age of 12, the doctor will use your child's age or weight to work out the right dose.
How to take it
Ferrous fumarate works best when you take it on an empty stomach. Take it 30 minutes before eating, or 2 hours after eating. But if it upsets your stomach, you can take it with or just after food.
Your doctor (or a pharmacist) may recommend taking ferrous fumarate with orange juice or a vitamin C supplement. Vitamin C is believed to increase the amount of iron absorbed by the body.
Swallow tablets or capsules with a glass of water or juice only. Do not take them with milk, as milk stops the iron getting into your system.
If you're taking ferrous fumarate as a liquid, it will come with a plastic syringe or spoon to help you measure the right dose. If you do not have one, ask your pharmacist for one. Do not use a kitchen teaspoon as you will not get the right amount.
Keep ferrous fumarate out of sight and reach of children, as an overdose may be fatal.
Ferrous fumarate is not harmful if it has been prescribed for your child and you follow your doctor's instructions, or the instructions on the packet.
What if I forget to take it?
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 one as normal.
- 3 times a day – skip the missed dose and take your next dose as normal.
Do not take a double dose to make up for a forgotten dose.
If you often forget doses, it may help to set an alarm to remind you. You could also ask a pharmacist for advice on other ways to remember your medicine.
What if I take too much?
If you go to A&E 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.
5. Side effects
Like all medicines, ferrous fumarate can cause side effects in some people.
Many people have no side effects or only minor ones.
Talk to your pharmacist or doctor 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
- dark or black poo
- black stained teeth (from the liquid only)
Serious allergic reaction
In rare cases it's possible to have a serious allergic reaction (anaphylaxis) to ferrous fumarate.
These are not all the side effects of ferrous fumarate.
For a full list, see the leaflet inside your medicines packet.
You can report any suspected side effect to the UK safety scheme.
6. How to cope with side effects
What to do about:
- feeling or being sick, stomach discomfort or heartburn – try taking ferrous fumarate with, or just after, a meal or snack. Stick to simple meals and do not eat rich or spicy food. If you're being sick, try small frequent sips of water to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
- loss of appetite – eat when you would usually expect to be hungry. If it helps, eat smaller meals more often than usual. Snack when you're hungry. Have nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
- constipation – eat more high-fibre foods such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to exercise more regularly, for example, by going for a daily walk or run. If this does not help, talk to a pharmacist or doctor. Watch this short video about how to treat constipation.
- diarrhoea – drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
- dark or black poo – this is common when taking iron and is nothing to worry about. Talk to a doctor if your poo is black and sticky looking, has red streaks in it, or if you also feel unwell in any other way.
- black stained teeth – rinse your mouth with water after taking the medicine.
7. Pregnancy and breastfeeding
It's usually safe to take ferrous fumarate during pregnancy.
Speak to a doctor, who'll be able to explain the benefits and the risks of taking ferrous fumarate when pregnant. They can help you decide on the best treatment for you and your baby.
If you are pregnant and taking iron supplements, it is common to become constipated or develop piles (haemorrhoids). If this happens to you, talk to a doctor. They can advise you on the best way to deal with constipation or haemorrhoids.
Ferrous fumarate and breastfeeding
It's usually safe to breastfeed while taking ferrous fumarate.
However, some of the medicine may pass into your breast milk. This is in small amounts and is unlikely to harm your baby.
Talk to a doctor if you want to breastfeed while taking ferrous fumarate. They can advise you on what's best for you and your baby.
Talk to a pharmacist or doctor if you're trying to get pregnant, already pregnant or breastfeeding.
8. Cautions with other medicines
There are some medicines that may interfere with how ferrous fumarate works.
Ferrous fumarate can also affect the way other medicines work. It is a good idea to leave a gap between taking the other medicine and ferrous fumarate. Ask a doctor or pharmacist for advice on how long the gap should be.
Before you start taking ferrous fumarate, tell a pharmacist or doctor if you're taking any of these medicines:
- supplements or multivitamins containing iron, calcium, magnesium or zinc, or you are already receiving iron injections
- antacid and indigestion remedies
- antibiotics such as oxytetracycline, doxycycline or ciprofloxacin
- antivirals used for HIV infection such as bictegravir or dolutegravir
- laxatives containing magnesium such as magnesium hydroxide and milk of magnesia
- medicines used to treat or prevent osteoporosis (bisphosphonates), such as alendronic acid and risedronate
- cholestyramine, a medicine used to reduce cholesterol
- eltrombopag, a medicine used to increase platelets in the blood
- levothyroxine, a medicine used to treat an underactive thyroid
- levodopa, carbidopa or entacapone, medicines used to treat Parkinson’s disease
- mycophenolate, a medicine used after an organ transplant
- methyldopa, a medicine used to treat high blood pressure
- penicillamine, a medicine used to treat arthritis
- trientine, a medicine used to treat Wilson's disease
Mixing ferrous fumarate with herbal remedies or supplements
Talk to a pharmacist or doctor before taking any herbal remedies or supplements together with ferrous fumarate. Some vitamin and mineral supplements may already contain ferrous fumarate.
Tell a pharmacist or doctor if you take any supplements or remedies that contain iron, calcium, magnesium or zinc. Ferrous fumarate can stop zinc working as well as it should.
Tell a doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.
9. Common questions
How does ferrous fumarate work?
How long does ferrous fumarate take to work?
How long will I take it for?
Is it safe to take for a long time?
How does it compare with other medicines for iron deficiency anaemia?
Will it give me more energy?
Can I drink alcohol with it?
Is there any food or drink I need to avoid?
Will it affect my contraception?
Will it affect my fertility?
Can I drive or ride a bike?
Can lifestyle changes help with iron deficiency?
Page last reviewed: 21/08/2019
Next review due: 21/08/2022