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 supplementation, such as:

  • pregnant women or teenage girls, who have higher iron requirements
  • those who do not absorb iron normally, such as people with renal failure or gut problems that cause malabsorption
  • anyone with ongoing or excessive blood loss, such as in women with heavy periods (menorrhagia).

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

If you have low iron levels, your doctor may prescribe, or your pharmacist may recommend, iron supplements to be taken by mouth (called oral iron supplements). In certain circumstances if oral iron supplements are not effective (that is, if they cannot be absorbed from your gut) or if they cannot be tolerated, iron supplements can be given by injection. Read more about iron injection.  

Iron supplements are also called:

  • Ferrous sulfate
  • Ferrous fumarate
  • Ferodan®
  • Ferro-Liquid®
  • Ferro-Tab®
  • Ferro-F Tab®
  • Ferrograd
  • Ferrograd C®
  • Ferro-Gradumet®


Note: Iron supplements should not be used by people with haemochromatosis, a rare condition that occurs when too much iron builds up in the body. The excess iron can cause damage to their organs.

  • Iron supplements are available on prescription, or you can buy them without a prescription from pharmacies, health stores or on the internet. 
  • There are a different forms of iron available in New Zealand, such as ferrous sulfate and 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 oral 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, so the choice of medicine is dependent on the risk of side effects and cost.
Examples of iron products in New Zealand  Description
  • Contains ferrous fumarate
  • Each 200 milligram tablet of Ferro-Tab®  has 65 milligrams of elemental iron
Ferro-gradumet® or Ferrograd®
  • Contains ferrous sulfate
  • Each 325 milligram tablet of Ferro-gradumet® or Ferrograd® has 105 milligrams of elemental iron
Ferodan® liquid
  • Contains ferrous sulfate
  • Each 5 milliliters (5 mL) of Ferodan® liquid has 30 milligrams of elemental iron

Some dietary supplements (such as Floradix) and multivitamins have small quantities of iron in them. The amount of iron in these products is not enough to treat iron deficiency. If you are unsure about the best supplement for you, talk to your doctor or pharmacist.

  • The dose needed will vary depending on whether the iron supplement is used to treat or prevent low iron levels.  
  • It is usually prescribed between 1 to 3 doses a day.
  • Always take your iron supplement exactly as your doctor 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 this medication with food.
  • Iron interacts with foods and beverages: Avoid having dairy products (milk), tea, coffee or antacids within 2 hours before or after this medication because they decrease its effectiveness.
  • Taking your dose with vitamin C: Taking vitamin C (such as orange juice or apple juice) with iron may increase its absorption, but there is 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. Do not lie down for at least 10 minutes after taking your dose.
  • Swallow extended-release tablets whole: Do not crush or chew extended-release tablets, as this will release all of the medication at once, increasing the risk of side effects. 
  • Measure you dose carefully: If you are taking the liquid form for adults, carefully measure the dose using a special measuring device or spoon. Do not use a household spoon because you may not get the correct dose.
  • Liquid forms can stain the teeth: Liquid iron can cause temporary discolouration of the teeth. To prevent staining, place the liquid on the back of your tongue with a dropper, use a straw or brush your teeth after each dose. 
  • It is 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. Do not 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 is not harmful when given to children in the amounts recommended by your doctor. You must not 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 are found to be iron deficient, you will 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 troublesome.
  • Constipation
  • This usually settles as your body gets used to the medication.
  • Tell your doctor or pharmacist if troublesome — 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.
  • You also need to eat more fibre, such as 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 troublesome. They may suggest a different
    iron preparation or a lower dose. Do not reduce the dose without discussing it with your doctor first. 
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product(external link)

  • Some multivitamin and mineral products may contain iron, so check with your doctor or pharmacist if you are taking these.
  • Some medicines available without a prescription may react with iron supplements, such as antacids (eg, Mylanta) or supplements containing aluminium (eg, Alu-Tab®), calcium (eg, Osteo®), magnesium (eg, Chelated Magnesium®) or zinc (eg, Zincaps®). Do not take these within 2 hours of taking iron supplements. Check with your pharmacist about any interactions.

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, 2019 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 is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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