Most people have an iron infusion without a serious problem. It is still a medical treatment, so you deserve a clear account of what can happen and what we do to prepare. Your clinician will discuss your own risks and options before you consent.
These figures come from the Ferinject medicine information. They describe groups of people who received that medicine; your own risk depends on your health and treatment plan. Skin staining does not have one dependable rate across NHS guidance, so we do not attach a misleading number to it.
Common
Up to 1 in 10 people
Headache, nausea, dizziness, flushing and a rise in blood pressure are listed as common effects of ferric carboxymaltose (Ferinject). Mild discomfort or bruising can also occur where the cannula goes in. Tell us if anything feels unusual while the infusion is running.
Frequency varies
A reliable personal percentage cannot be given
If iron leaks outside the vein, it can cause pain, swelling and brown skin staining. The mark may fade slowly or be permanent. Tell your clinician immediately about pain, burning, swelling or a change in colour around the cannula, even if it seems minor, so the infusion can be stopped and checked.
Common blood-test finding
At least 1 in 100 and fewer than 1 in 10
Ferinject can lower the phosphate level in your blood, often without symptoms. The risk of troublesome low phosphate matters more with repeated high-dose treatment or existing risk factors. Rarely, prolonged low phosphate can affect bones. Tell a clinician if new or worsening tiredness, muscle weakness or bone pain develops in the following days or weeks; a blood test may be needed.
Rare
At least 1 in 10,000 and fewer than 1 in 1,000
A serious reaction can cause breathing difficulty, wheezing, swelling of the face or throat, a widespread rash, faintness or collapse. It is rare but can be life-threatening. Tell the team straight away if you feel unwell during treatment. The published range is for Ferinject generally, not a measured IronOx rate or a prediction for one person.
Other possible effects include rash, itching, muscle or joint aches and flu-like symptoms. Some reactions can begin hours or days after treatment. This page covers the main risks and does not replace the patient leaflet or your consent discussion.
At IronOx, a doctor reviews your blood results, medical history, medicines and previous reactions before treatment. A trained doctor or advanced nurse practitioner monitors the infusion and you remain under observation for at least 30 minutes afterwards.
The clinical team has an emergency response process, with an emergency trolley, resuscitation equipment and an AED on site. Dr Ros has an acute medicine and A&E background and is trained to recognise and manage anaphylaxis. These precautions help the team respond promptly if a reaction occurs; they cannot remove every risk.
If you have trouble breathing, swelling of the face or throat, or feel faint or collapse after leaving, call 999 immediately. Tell them you recently had an iron infusion.
Contact IronOx or your GP about persistent or worsening tiredness, muscle weakness, bone pain, rash, or concerns about staining. Your clinician can advise whether a phosphate test or other review is needed.
You can read more about what happens at your appointment and contact the clinic with questions before booking.
This patient information was prepared from the sources below and the IronOx consent topics. Clinical suitability and personal risk are assessed by your treating clinician. Last updated 23 September 2026.
