Transferrin Saturation
The percentage of transferrin that is actually carrying iron — a key marker of iron status (low in deficiency, high in overload).
Typical reference range
| Range | Unit |
|---|---|
| 20–45 | % |
What Transferrin Saturation measures
Transferrin saturation is the percentage of your iron-carrying protein, transferrin, that is actually loaded with iron at the time of the blood draw. In simple terms, it shows how full the body's iron transport system is: a low percentage means the carriers are mostly empty, while a high percentage means they are largely occupied.
It is a core part of the iron studies panel and is read alongside serum iron, transferrin or TIBC, and ferritin. Because it combines information about how much iron is circulating and how much carrier protein is available, it helps show whether iron supply looks high or low. Clinicians rarely interpret it on its own, preferring to weigh the whole panel together.
What a high Transferrin Saturation can mean
A higher-than-expected transferrin saturation suggests that a large share of the carrier protein is loaded with iron, which can point toward the body carrying more iron than usual.
- Iron overload conditions, including hereditary hemochromatosis, which is typically read together with a high ferritin as well.
- Repeated blood transfusions, which add extra iron to the body over time.
- Recent iron supplements or a high-iron intake before the blood draw, which can lift a single reading.
A persistently high value is often what prompts a clinician to consider further iron-overload evaluation, especially when it appears alongside a raised ferritin. Because an isolated result can be influenced by diet and supplements, it is best understood within the full iron panel and your history. A clinician can look at the pattern across markers before drawing any conclusions.
What a low Transferrin Saturation can mean
A lower-than-expected transferrin saturation means that relatively little iron is loaded onto the available carrier protein, which commonly reflects a shortage of iron.
- Iron deficiency is a frequent explanation: there is little iron to bind to a lot of carrier protein, and this is often seen alongside a low ferritin.
- Inflammation can also lower transferrin saturation even when stores are not truly depleted, which is one reason the marker is not read in isolation.
Because a low value can reflect either genuine deficiency or a temporary shift, it is best interpreted within the full iron panel rather than on its own. A clinician can weigh this result together with related markers, your symptoms, and your history, and advise on whether any next steps are worthwhile.
Track your Transferrin Saturation over time in Quanome — it reads your lab reports (PDF or photo) on your device, charts each marker against its range, and an AI coach explains what your trends mean alongside your Apple Health and DNA.