The aim of this study is to track where the iron goes in different tissues in the hours, days and weeks after an intravenous iron infusion. We will track iron in tissues using MRI relaxometry parameters R1/R2/R2* which are well established as accurate indicators of tissue iron content.

This is a prospective, observational, study exploring the kinetics of tissue iron uptake following intravenous iron infusion (Ferinject), received as part of standard clinical care in a group of iron-deficient patients.

Participants will be recruited through the Iron Deficiency Management Service, part of the Oxford University Hospitals NHS Foundation Trust (OUHFT) . Participants will receive their intravenous iron infusion (Ferinject) as part of their standard clinical care by an NHS clinician. They will undergo all the study MRI scans and additional study procedures at the Oxford Centre for Clinical Magnetic Resonance Research (OCMR), which is based at the John Radcliffe Hospital and is part of the Division of Cardiovascular Medicine within the Radcliffe Department of Medicine at the University of Oxford.

Each participant will undergo 4 MRI scans; baseline, 3hours, 14 days and 42 days post intravenous iron infusion. Blood samples will also be collected at those timepoints for assessment of relevant heamatological and iron parameters.

Inclusion Criteria:

• Participant is willing and able to give informed consent for participation in the study.
• Aged 18 years or above.
• Anaemia (haemoglobin less than 120g/L for women and less than 130g/L for men) and/or confirmed iron deficiency (ferritin less than 100mcg/L and/or transferrin saturation less than 20%).
• Scheduled to receive intravenous iron for correction of iron deficiency.

Exclusion Criteria:

• Any MRI incompatible implants (e.g. cardiac, neuro, ocular implants, surgical clips, aneurysm clips, shrapnel/bullets)
• Pregnant or lactating participant
• Acute decompensated heart failure
• Unstable clinical status
• Any other medical conditions which would influence the reliability of the study results determined by the investigators.
• Any other contraindication to MRI to be confirmed by the qualified MRI operator, e.g. tattoos containing traces of metal.

Participants are patients who require intravenous iron as part of their standard clinical care. They will be recruited from referrals to the Iron Deficiency Management Service (IDMS), part of Oxford University Hospitals NHS Foundation Trust (OUHFT). This service receives referrals from multiple sources across Oxfordshire.

Patient referrals will be screened by members of the NHS Clinical team at IDMS to identify potentially eligible participants.