Iron studies
Transferrin saturation blood test
Transferrin saturation is the percentage of your blood's iron-transport capacity that is actually carrying iron. It's a central part of iron studies: a low saturation points towards iron deficiency, while a high saturation is one of the earliest signs of iron overload.
- What it measures
- The percentage of your iron-transport capacity currently carrying iron
- Sample
- Venous blood sample
- Fasting
- Preferred (a morning sample is best)
- Also known as
- TSAT, transferrin sat
- Included in 57 Health tests
- 6 panels, from £95
Transferrin saturation reference range
Guide only| Category | Guide range |
|---|---|
| Adults | 20–50 % |
Below about 20% suggests iron deficiency; above roughly 45–50% raises the possibility of iron overload (such as haemochromatosis). It's calculated from serum iron and TIBC, and interpreted alongside ferritin.
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 transferrin saturation level mean?
A high transferrin saturation is one of the earliest and most useful signs of iron overload, including hereditary haemochromatosis, and usually prompts a check of ferritin and, where relevant, genetic testing.
It can also rise temporarily after iron supplements, so it's confirmed on a fasting morning sample alongside ferritin.
What does a low transferrin saturation level mean?
A low transferrin saturation suggests there isn't enough iron to fill the available transport capacity, typically iron deficiency.
It's interpreted with ferritin (which is usually also low in true deficiency) and TIBC, since inflammation can affect these markers differently.
When to consider a transferrin saturation test
- Suspected iron deficiency
- Screening for or investigating iron overload / haemochromatosis
- Ongoing fatigue with a family history of haemochromatosis
- As part of full iron studies
Frequently asked questions
This page is general information about a blood marker and is not medical advice or a diagnosis. A transferrin saturation 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.