Iron supplements (oral)

Key points about oral iron supplements

  • Iron supplements are used to treat or prevent low levels of iron in your blood (also called iron deficiency anaemia).
  • They increase the amount of iron stores in your body.
  • Find out how to take them safely and possible side effects.
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Iron supplements are used to treat or prevent low levels of iron in your blood (iron deficiency). They increase the amount of iron stores in your body. Most people get enough iron from a healthy, balanced diet. However, some people may need iron supplements, including:

  • pregnant women or teenage girls, who have higher iron requirements
  • people who don't absorb iron well, eg, people with renal failure or gut problems that cause malabsorption
  • anyone with ongoing or excessive blood loss, eg, women with heavy periods (menorrhagia).

Some babies and children may need iron supplements. Read more about iron supplements for babies and children.

Types of iron supplements

  • Iron supplements are available on prescription, or you can buy them without a prescription from pharmacies, health stores or on the internet. 
  • There are different forms of iron available in Aotearoa New Zealand, including iron polymaltose, ferrous sulfate, ferrous fumarate (ferrous is the Latin word to describe iron).
  • Each of these has a different amount of actual iron (called elemental iron).
  • The usual dose of elemental iron to treat iron-deficiency is 100 to 200 mg daily. Lower doses may be used to prevent iron-deficiency.
  • There is no particular advantage of one type over another, as long as you receive enough elemental iron. The choice of medicine is dependent on the risk of side effects and cost. Some options may fewer side effects (eg, stomach upset), some are funded and some are not. Talk to your healthcare provider about this.
  • Some dietary supplements (eg, Floradix) and multivitamins have small quantities of iron in them. The amount of iron in these products isn't enough to treat iron deficiency. If you're not sure about the best supplement for you, talk to your doctor or pharmacist.
  • Iron supplements can be given by injection for people who have problems taking them by mouth (as tablets, capsules or liquid) because they cannot be absorbed from the gut or because they can't be tolerated due to side effects. Read more about iron injection.

Examples of iron products in New Zealand  Description
  • Contains ferrous fumarate
  • Each 200 mg tablet of Ferro-Tab® has 65 mg of elemental iron
Ferro-gradumet® or Ferrograd®
  • Contains ferrous sulfate
  • Each 325 mg tablet of Ferro-gradumet® or Ferrograd® has 105 mg of elemental iron
Ferodan® liquid
  • Contains ferrous sulfate
  • Each 10 mL of Ferodan® liquid has 60 mg of elemental iron
Maltofer® tablets and liquid
  • Contains iron polymaltose
  • Each 370 mg tablet of Maltofer contains 100 mg of elemental iron
  • Each 10 mL of Maltofer liquid has 100 mg of elemental iron

  • The dose you need will vary depending on whether the iron supplement is used to treat or prevent low iron levels.  
  • 1 to 3 doses a day are usually prescribed.
  • Always take your iron supplement exactly as your doctor or pharmacist has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it and any special instructions. Talk to your doctor or pharmacist if you have any questions regarding your medication or dosage. 

  • Take on an empty stomach: Iron supplements are best taken on an empty stomach (usually 1 hour before or 2 hours after meals). But, if you get an upset stomach or you feel sick (queasy), you can take iron with food.
  • Iron interacts with some foods and beverages: Avoid having dairy products (milk), tea, coffee or antacids in the 2 hours before or after taking iron because it won't work as well.
  • Other medicines: Iron supplements interact with some medicines, herbal supplements and rongoā Māori, so check with your doctor or pharmacist before starting iron supplements and before starting any new products. Some medicines available without a prescription may react with iron supplements (eg, antacids, or supplements containing aluminium, calcium, magnesium or zinc). Don't take these within 2 hours of taking iron supplements. 
  • Taking your dose with vitamin C: Taking vitamin C (eg, orange or apple juice) with iron may improve its absorption, but there's very limited evidence to support this.
  • Tablets or capsules can irritate your gut: Take your iron tablets or capsules with a full glass of water. Don't lie down for at least 10 minutes after taking your dose.
  • Swallow extended-release tablets whole: Don't crush or chew extended-release tablets, as this will release all of the medicine at once, increasing the risk of side effects. 
  • Measure your dose carefully: If you're taking the liquid form, carefully measure the dose using a special measuring device or spoon. Don't use a household spoon because you may not get the correct dose.
  • Liquid forms can stain teeth: Liquid iron can stain your teeth. To prevent staining, place the liquid on the back of your tongue with a dropper, use a straw or brush your teeth straight after each dose. 
  • It's not harmful if you miss a dose of your iron supplement: If you miss a dose, just take your next dose at the right time. Don't take double the dose.
  • Storage: Remember to keep iron supplements out of the reach and sight of children, because an overdose may be fatal. (Iron isn't harmful when given to children in the amounts recommended by your doctor. You mustn't give your child more than this).

The length of treatment will depend on how low your iron levels are. To diagnose iron deficiency your doctor will recommend you have a blood test, and if you're found to be iron deficient, you'll be prescribed iron supplements. A few weeks after taking iron supplements, you will have another blood test to check if the supplements are working. When your blood level is back to normal, you should continue to take iron for at least 3 further months. This will build up the stores of iron in your body. 

Like all medicines, iron supplements can cause side effects, although not everyone gets them. Often effects improve as your body gets used to the new medicine.  

Side effects What should I do?
  • Dark or black-coloured stools (poos)
  • Iron supplements can make your stools look darker in colour.
  • This is common and usually nothing to worry about, but can also
    be a sign of bleeding.
  • Talk to your doctor.
  • Feeling sick (nausea)
  • Try taking your iron supplement with food.
  • Tell your doctor or pharmacist if this bothers you.
  • Constipation
  • This usually settles as your body gets used to the medication.
  • Tell your doctor or pharmacist if you're having problems – you may need a suitable laxative, which you need to take on a regular basis, or your doctor or pharmacist may recommend taking a lower dose or a different preparation.
  • You also need to eat more fibre, eg, kiwifruit, vegetables, brown bread or bran-based breakfast cereals, and drink plenty of water.
  • Diarrhoea or loose stool 
  • This usually settles as your body gets used to the medication.
  • Tell your doctor or pharmacist if it bothers you. They may suggest a different
    iron preparation or a lower dose. Don't reduce the dose without discussing it with your doctor first. 

Read more about medicines and side effects(external link) and reporting a reaction that you think might be a side effect(external link).

The following links have more information on iron supplements. 

Iron supplements(external link) New Zealand Formulary 
Ferrous fumarate for iron-deficiency anaemia(external link) New Zealand Formulary Children
Ferrous sulfate for iron-deficiency anaemia(external link) New Zealand Formulary Children


5 questions to ask about your medications(external link) Health Quality and Safety Commission, NZ English(external link), te reo Māori(external link)


  1. Oral iron(external link) New Zealand Formulary

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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