Anaemia (low haemoglobin levels) can develop in a number of conditions, including chronic kidney disease (CKD) and intestinal conditions (e.g. inflammatory bowel disease, intestinal failure). Intravenous iron can be given to patients with these conditions to help correct their aneaemia. However, intravenous iron has been associated with the development of low phosphate levels - hypophophosphataemia. The aim of this study is to determine potential causes of hypophosphataemia following administration of intravenous iron.

Low levels of iron can lead to anaemia, known as iron deficiency anaemia, which can be debilitating due to symptoms such as shortness of breath, fatigue, and dizziness. Iron deficiency anaemia can be treated by giving iron supplementation. Iron supplements can be taken orally or can be given intravenously (through the veins). Giving iron intravenously has advantages over iron supplements taken orally, which can cause side effects such as stomach pain and cramping. However, giving iron intravenously has been associated with the development of low levels of phosphate in the blood. This is known as hypophosphataemia. Phosphate is an important salt in the body and has a number of important functions. Very low levels of phosphate can cause muscle pain, disorientation, seizures and heart problems. It is unclear why giving iron intravenously can cause hypophosphataemia. This project aims to investigate the potential causes of hypophosphataemia in patients who receive intravenous iron as treatment for anaemia associated with their condition. Patients with chronic kidney disease (CKD) and intestinal failure will be recruited to the study, since people with CKD may handle iron differently than those with healthy kidneys. Samples will be taken at two time points: prior to giving the intravenous iron and at the patient's next appointment. Healthy volunteers will also be recruited to the study to allow comparison between the groups receiving iron and those who do not receive iron. Samples will be analysed to determine potential causes of hypophosphataemia. Results from before and after iron is given will be compared to determine if any of the participants developed hypophosphataemia and if any other test are affected which may explain why this has developed.

Inclusion Criteria:

For Patients

• aged 18 years or older
• previously diagnosed with intestinal failure or advanced CKD
• have anaemia requiring administration of intravenous iron
• be able to adequately speak and understand English
• Have capacity to give written informed consent

For Healthy Volunteers

• aged 18 years or more
• be able to adequately speak and understand English
• have capacity to give written informed consent

Exclusion Criteria:

For patients

• have dialysis-dependent CKD
• participation in any other study which will affect results of the current study

For Healthy Volunteers

• have CKD (eGFR <60 mls/min/1.73^2)
• history of any form of metabolic bone disease
• Participation in any other study which will affect the results of the current study

Patients with intestinal failure or CKD will be recruited from iron infusion clinics, which are based in secondary care. Healthy Volunteers will be recruited from laboratory staff from within the Belfast Health and Social Care Trust