Iron studies
TIBC blood test
A TIBC (total iron-binding capacity) blood test measures how much iron your blood could carry if it were fully loaded, essentially the spare capacity of transferrin, the protein that transports iron. It rises when iron is in short supply and falls when there's plenty, so it's a useful part of iron studies read alongside iron, ferritin and transferrin saturation.
- What it measures
- Total iron-binding capacity (how much iron your blood could carry)
- Sample
- Venous blood sample
- Fasting
- Not required (a morning sample is preferred for iron studies)
- Also known as
- total iron-binding capacity
- Included in 57 Health tests
- 6 panels, from £95
TIBC reference range
Guide only| Category | Guide range |
|---|---|
| Adults | 45–70 µmol/L |
TIBC rises when iron stores are low (the body makes more transferrin to capture iron) and falls with iron overload or chronic illness. It's interpreted together with iron, ferritin and transferrin saturation rather than alone.
These are general UK adult guide ranges from public health sources, shown for orientation only. Reference ranges vary by laboratory, assay, age and sex, so your result is always interpreted against the range quoted by the analysing laboratory on your report.
What does a high TIBC level mean?
A high TIBC usually indicates iron deficiency: when iron is scarce, the body makes more transferrin to capture whatever iron it can, raising the total binding capacity.
TIBC can also be higher in pregnancy and with the combined oral contraceptive pill. It's confirmed as iron deficiency by looking at ferritin (low) and transferrin saturation (low) alongside it.
What does a low TIBC level mean?
A low TIBC can occur with iron overload, or with chronic illness and inflammation, where the body makes less transferrin.
It can also fall when the body is losing protein or is malnourished, so it's interpreted with ferritin and transferrin saturation to understand the whole iron picture.
When to consider a TIBC test
- Suspected iron deficiency or anaemia
- Ongoing tiredness or low energy
- As part of full iron studies
- Investigating possible iron overload
- Monitoring iron status over time
Frequently asked questions
This page is general information about a blood marker and is not medical advice or a diagnosis. A TIBC test screens and gives context; results are interpreted by a clinician alongside your symptoms, history and other markers. Always follow the guidance on your own report.