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Iron supplements

Iron supplements are best absorbed when they are taken an hour before meals. However, to reduce stomach upset, you may prefer to take your doses after meals.

Common side-effects include stomach upset, constipation and diarrhoea.

Remember to keep iron supplements out of the reach and sight of children - iron is a common cause of serious accidental ingestion in children.

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About iron supplements

Type of medicine

Oral iron

Used for

Prevention and treatment of iron-deficiency anaemia

Also called

Ferrous sulfate, ferrous fumarate, ferrous gluconate, sodium feredetate, polysaccharide-iron complex

Available as

Tablets, capsules, oral liquid medicine, oral liquid sachets and oral drops

Iron-deficiency anaemia is caused by a lack of iron. Iron is needed to make haemoglobin which carries oxygen around in the bloodstream and is what makes red blood cells red.

If you have iron-deficiency anaemia, it means that there is a reduced amount of oxygen being carried around in your body. This can cause tiredness, breathlessness, dizziness, the sensation of having a 'thumping heart' (palpitations) and headache.

Iron is found naturally in certain foods, but in conditions where people do not get enough iron from their normal diet for their body's needs, an iron supplement may be useful.

Before taking iron supplements

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking an iron supplement it is important that your doctor or pharmacist knows:

  • If you have any difficulty swallowing.

  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

  • If you have ever had an allergic reaction to a medicine.

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How to take iron supplements

  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about the iron supplement and will provide you with a full list of the side-effects which you may experience from taking it.

  • Iron is absorbed into your bloodstream best if the supplement is taken about an hour before a meal. If, however, you feel queasy after taking iron, having some food in your stomach can help to reduce stomach irritation and feelings of queasiness. So in this case, it may be better for you to take your iron supplement just after a meal.

  • Take the iron preparation exactly as your doctor tells you to. You will be told how much to take and how often to take it. Your dose will also be on the label of the pack to remind you. It is usual to be prescribed between 1-3 doses a day. Taking your doses at the same times each day will help you to avoid missing any.

  • If you do forget to take a dose, don't worry, just leave out the missed dose and take the next dose when it is due. Do not take two doses together to make up for a forgotten dose.

Getting the most from your treatment

  • The length of your course of treatment will depend upon how low your iron levels are. A blood test after a few weeks will show if the treatment is working and your doctor will tell you for how long you should continue to take the iron supplement.

  • If you buy any medicines, check with your pharmacist that they are suitable to take with iron supplements. Some medicines (particularly antacids) can interfere with the way iron is absorbed and so should not be taken at the same time.

  • Iron supplements can make your stools look darker in colour. This is completely harmless.

  • If you suspect that you have taken an overdose of iron, or that someone else (especially if it is a child) might have taken it accidentally, go to the accident and emergency department of your local hospital straightaway. This is very important because iron can cause serious problems when it is taken accidentally or in overdose. Take the container with you to show what has been taken, even if the pack is now empty.

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Can iron supplements cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with iron. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common iron side-effects

What can I do if I experience this?

Feeling sick (nausea), stomach pain

Stick to simple foods. If you are not already doing so, take your doses after meals


Try to eat a well-balanced diet and drink several glasses of water each day


Drink plenty of water to replace lost fluids

If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for further advice.

How to store iron supplements

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

If you are having an operation or any dental treatment, tell the person carrying out the treatment which medicines you are taking.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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