Iron supplements taken by mouth

• The dose you'll need will vary depending on whether the iron supplement is used to treat or prevent low iron levels.  
• The usual dose of elemental iron to treat iron-deficiency in adults is 100 to 200 mg daily. Lower doses may be used to prevent iron-deficiency.
• You'll be advised to take your dose between 1 to 3 times a day.
• Always take your iron supplement exactly as your healthcare provider 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. 

• Take on an empty stomach: Iron supplements are best taken on an empty stomach (usually 1 hour before or 2 hours after meals). If you get a sore tummy or you feel sick (nausea), take it with food.
• Tablets or capsules: These can irritate your gut, so 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.
• Extended-release tablets: Swallow these tablets whole. Don't crush or chew extended-release tablets, as this will release all of the medicine at once and increase the risk of side effects. 
• Liquid iron: If you're taking the liquid form, carefully measure the dose using a special measuring device or spoon. Don't use a kitchen spoon because you may not get the correct dose.
• Missed 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.

Here are some things to know when you're taking iron supplements. Other things may be important as well, so ask your healthcare provider what you should know about.

• Foods and drinks: Iron interacts with some foods and drinks. Don’t drink milk, tea, or coffee for 2 hours before or after taking iron, as they can stop your body from absorbing the iron properly.
• Other medicines: Iron supplements interact with some medicines such a antacids for indigestion, herbal supplements and rongoā Māori, so check with your healthcare provider or pharmacist before starting iron supplements and before starting any new products. Don't take antacids within 2 hours of taking iron supplements. 
• Other supplements: Don't take any supplements containing aluminium, calcium, magnesium or zinc within 2 hours of taking iron supplements.
• Liquid iron: Iron supplements in liquid form 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.
• How long to take iron for: The length of treatment will depend on how low your iron levels are. Your healthcare provider will ask you to have a blood test to see how well the medicine is working. Using this information they'll tell you how long to continue taking your iron supplement. When your blood level is back to normal, you should continue taking iron for at least another 3 months. This will build up the stores of iron in your body. 
• Storage: Remember to keep iron supplements out of the reach and sight of children, because an overdose can be very dangerous. If you think a child or someone else has taken a medicine that is not for them call the New Zealand National Poisons Centre(external link) immediately on 0800 764 766 for advice. Read more about what you can do in the event of a poisoning.
• 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. 

Like all medicines, iron supplements can cause side effects, although not everyone gets them. If you're concerned about any symptoms you think might be related to your medicine, talk to your healthcare provider. The following information offers some guidance but doesn't include all possible side effects.

Common side effects

Tell your healthcare provider if these side effects bother you.

• Dark or black-coloured stools (poo): 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 healthcare provider if you’re concerned.
• Nausea (feeling sick): Try taking your iron supplement with food.
• Constipation: Tell your healthcare provider or pharmacist if you're having problems. They may suggest taking a laxative, taking a different iron supplement or taking your iron every second day. Eat more fibre, eg, kiwifruit, vegetables, brown bread or bran-based breakfast cereals, and drink plenty of water.
• Diarrhoea (runny poo): Tell your healthcare provider or pharmacist if you're having problems, they may suggest a different iron supplement or a lower dose. Don't reduce the dose without discussing it with them first. 
   

Phone 111 for an ambulance or go to your nearest accident and emergency (A&E) clinic if these occur

• Signs of an allergic reaction such as itchy skin, and rash, swollen lips or tongue, problems breathing, like a tight chest or shortness of breath.
   

Read more about medicines and side effects and reporting a reaction you think might be a side effect.