Haematology
Intravenous iron
Iron infusions — Iron given by drip to correct iron deficiency quickly when tablets are not enough or not tolerated.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
Quick answer
What is Intravenous iron?
Intravenous iron delivers iron directly into a vein to treat iron deficiency and iron-deficiency anaemia. It is used when iron tablets are ineffective, not tolerated, or too slow, and can restore iron stores quickly in one or a few sessions.
- How it works: It supplies iron straight into the bloodstream, bypassing the gut, where it is taken up and used to make haemoglobin and refill the body's iron stores.
- In practice: In practice intravenous iron is used to correct iron deficiency (with or without anaemia) when oral iron does not work, is not tolerated, or cannot keep up with losses — for example in significant gut disease (where tablets are poorly absorbed or worsen symptoms), chronic kidney disease, heart failure, ongoing bleeding, or when iron stores must be restored quickly (such as later pregnancy or before surgery).
What it is
Intravenous iron delivers iron directly into a vein to treat iron deficiency and iron-deficiency anaemia. It is used when iron tablets are ineffective, not tolerated, or too slow, and can restore iron stores quickly in one or a few sessions.
How it works
It supplies iron straight into the bloodstream, bypassing the gut, where it is taken up and used to make haemoglobin and refill the body's iron stores. Bypassing absorption is what makes it reliable when the gut cannot absorb tablets, or when iron is being lost faster than tablets can replace it.
In practice
In practice intravenous iron is used to correct iron deficiency (with or without anaemia) when oral iron does not work, is not tolerated, or cannot keep up with losses — for example in significant gut disease (where tablets are poorly absorbed or worsen symptoms), chronic kidney disease, heart failure, ongoing bleeding, or when iron stores must be restored quickly (such as later pregnancy or before surgery). Its advantages are reliable replenishment of iron stores in one or a few visits and avoidance of the constipation and nausea of oral iron. Modern formulations allow large amounts to be given safely in a single infusion. The main practical themes are: a small risk of reactions during the infusion (from mild to, rarely, serious allergic reactions), so it is given where staff and resuscitation facilities are available and the person is observed; a fairly common, harmless transient flushing or aches that must not be mistaken for true allergy and managed by slowing the infusion; the risk of staining the skin brown if it leaks at the drip site (so the cannula is watched); and, with some preparations, a temporary drop in phosphate. It is generally avoided in the first trimester of pregnancy and in active infection.
Examples
Practical use
How to take it & use it well
- This is iron given into a vein in a clinic or hospital, used to correct iron deficiency when iron tablets have not worked, are not tolerated, or when iron is needed more quickly.
- It is given by a trained team who monitor you during and shortly after the infusion, as a small number of people can have a reaction.
- Tell the team straight away if you feel flushing, tightness in the chest, wheeze, dizziness or swelling during the drip, as they are ready to deal with reactions promptly.
- Mild flushing, a metallic taste or aches during or after the infusion are usually harmless and pass, and are not the same as a true allergy.
- The team takes care that the iron does not leak from the drip into the skin, as this can leave a long-lasting brown stain, so tell them at once if the site stings or swells.
- Attend any follow-up blood tests, as your iron and blood count are rechecked later to see how well the treatment has worked and whether more is needed.
Common uses
- Iron deficiency when oral iron fails or is not tolerated
- Iron deficiency in kidney disease, heart failure or gut disease
- Rapid replacement (e.g. later pregnancy, before surgery, ongoing bleeding)
Monitoring
- Haemoglobin and iron stores (ferritin, transferrin saturation) in response
- Infusion reactions and the cannula site
- Phosphate with certain preparations; underlying cause of the deficiency
Weighing it up
Advantages & disadvantages
Advantages
- It corrects iron deficiency reliably, even when iron tablets have failed or cannot be tolerated.
- It restores iron stores faster than tablets, which is useful when iron is needed quickly.
- It avoids the stomach upset and constipation that iron tablets often cause.
- It is helpful for people whose gut does not absorb iron well or who lose iron faster than tablets can replace.
- It can lift tiredness and other symptoms of iron deficiency once stores are rebuilt.
Disadvantages
- There is a small risk of an infusion reaction, including a rare but serious allergic reaction, so it is given with monitoring.
- It must be given in a clinic or hospital setting rather than taken at home as a tablet.
- If it leaks from the drip into the skin it can leave a lasting brown stain.
- Some of these treatments can lower the blood phosphate level, which may need checking.
- It is generally avoided in early pregnancy and during an active infection.
Key safety principles
What to watch for
- Small risk of infusion reactions (mild to, rarely, serious allergic reactions) — given with monitoring where resuscitation facilities are available.
- Transient flushing or aches during the infusion are usually harmless and managed by slowing it — not the same as a true allergy.
- Can stain the skin if it leaks at the drip site (cannula watched); some preparations lower phosphate; avoided in the first trimester and active infection.
Key interactions
What to avoid or check alongside
- It is best avoided while you have an active infection, as added iron may not be wise until the infection has settled.
- Some forms can lower the blood phosphate level, so this is sometimes checked, especially with repeated treatment.
- There is usually no need to take iron tablets at the same time, and your team will advise whether to pause them around the infusion.
- Tell the team about any previous reaction to an iron infusion or other medicines, as this guides how the treatment is given.
- It is generally avoided in the first three months of pregnancy, with infusions left until later if iron is still needed.
Patient & carer advice
- Tell the team at once about any wheeze, rash, swelling or feeling faint during the infusion
- Some flushing or mild aches can happen and usually settle — it is not an allergy
- It restores your iron quickly, but we will also look for and treat the cause of the deficiency
Use with
Related clinical calculators
Dose and risk decisions for this class often depend on renal function, weight or bleeding/stroke risk. These tools help:
Answers
Intravenous iron: frequently asked questions
Why am I having iron through a drip instead of tablets?
Iron given into a vein is used when tablets have not worked, cannot be tolerated because of stomach upset, or when iron stores need rebuilding faster than tablets can manage. It is also useful when the gut does not absorb iron well. It restores iron reliably, though it must be given in a clinic with monitoring.
Is an iron infusion safe?
For most people it is given without problems, but there is a small risk of an infusion reaction, including a rare but serious allergic reaction, which is why a trained team monitors you during and after it. Tell them at once about flushing, chest tightness, wheeze or swelling so they can act quickly.
Is flushing during the infusion an allergy?
Usually not. Mild flushing, a metallic taste or aches during or after the drip are common and harmless, and they pass on their own. They are not the same as a true allergic reaction. Even so, tell the team about anything you feel, so they can check and slow or pause the drip if needed.
What is the brown mark some people get?
If the iron leaks out of the vein into the surrounding skin during the infusion, it can leave a brown stain that may last a long time. The team takes care to avoid this, but tell them straight away if the drip site stings, burns or swells, so they can stop and check before any leak gets worse.
Can I have an iron infusion in pregnancy?
Iron infusions are generally avoided in the first three months of pregnancy, with treatment usually left until later if iron is still needed. They are also avoided during an active infection. Your team will weigh up the timing and your needs, so tell them if you are or might be pregnant.
Authoritative sources
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