Iron and energy
Normal Transferrin Saturation Levels, Read Properly
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed September 20265 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
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North West London Pathology prints a transferrin saturation range of 16 to 55%. UK labs use the number mainly to look for iron overload: above 50% in men, or above 40% in women, prompts further investigation. For suspected iron deficiency, they ask you to request ferritin instead.
Not sure which markers you need? Build your test →Your iron studies came back with a saturation figure and no explanation. Maybe 18%. Maybe 47%. Neither number means much on its own, and that is not your fault.
Transferrin is the protein that ferries iron around your blood. Saturation is the percentage of its carrying seats that are full. So it describes iron in transit, not iron in the bank.
1. What is a normal transferrin saturation?
North West London Pathology publishes 16 to 55%. It describes the test as measuring what proportion of available iron-binding sites on transferrin are carrying iron.
Other UK labs print different figures, and several print no range at all. They publish an action threshold instead. So read your number against the range on your own report, not against one you found online.
There is a reason the ranges wander. Saturation is not measured directly. As Royal United Hospitals Bath puts it, it is a calculated test, derived from measurement of iron and transferrin. Two measurements go in, so two sets of variation come out.
The same adult range applies at every age. There is no saturation chart by decade.
2. The number it is really there for
Iron overload. Specifically haemochromatosis, an inherited condition where the body absorbs more iron than it needs. On this, UK labs agree closely.
| Laboratory | Threshold |
|---|---|
| Royal United Hospitals Bath | Above 50% men, above 40% women |
| North Bristol NHS Trust | Above 50% men, above 40% women |
| Gloucestershire Hospitals | Above 50% men, above 40% women |
Crossing that line is not a diagnosis. It is the point at which a clinician looks further, usually with ferritin and sometimes with a genetic test.
A high saturation with a high ferritin is the pattern that gets attention. Our guide on high ferritin levels covers the other half of that picture.
3. Why your lab wants ferritin instead
Most people arrive at this test from the other direction. They are tired, they suspect low iron, and saturation looks like the precise answer. UK labs disagree, and one of them says so on the test page itself.
“For investigation of possible iron deficiency anaemia please request FERRITIN (not transferrin saturation).”
— Royal United Hospitals Bath, pathology test information
Ferritin is the protein that holds iron in reserve, so it shows how much iron you have banked. Saturation shows how much is moving right now. For a first look at low iron, the bank is the better question.
There is one clear exception. Royal United Hospitals Bath notes that saturation gives a better measure of iron status than ferritin in people with end stage kidney failure on haemodialysis. Ferritin climbs with inflammation, and that setting has plenty of it.
4. What moves your saturation
More than you would expect, which is why one reading rarely settles anything.
- This morning's iron tablet. Serum iron jumps after a dose, and the saturation follows it up.
- The time of day. Serum iron drifts across the day, so a morning sample and an afternoon one are not the same test.
- Recent illness or inflammation. It pulls iron out of circulation, which lowers the saturation.
- Pregnancy and the contraceptive pill. Both change how much transferrin your liver makes.
Practical version: take a morning sample, leave that day's iron supplement off, and do not read a single figure as settled. Our guide on the full blood count covers the markers a clinician reads alongside it.
5. Which blood test reports your saturation
You need iron and transferrin measured together, because the saturation is calculated from both. A ferritin result on its own cannot produce it.
Helvy's Vitamins & Minerals panel (£159) reports transferrin saturation as part of a full iron workup: iron, ferritin, transferrin, total iron binding capacity and the saturation itself, read next to vitamin B12, folate, vitamin D and magnesium. The grouping matters, because B12 and folate explain a good deal of the tiredness people blame on iron.
One honest limit. This is not a full anaemia screen. That also needs a full blood count and a clinical judgement, so our report shows how your iron markers sit rather than reaching a diagnosis. To pick your own markers, the build-my-test tool walks you through it.
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See the whole iron workup, not one number from it
Helvy's home blood tests report transferrin saturation with plain-English context, alongside iron, ferritin, transferrin and TIBC. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
What is a normal transferrin saturation in the UK?
North West London Pathology publishes 16 to 55%. UK labs vary, and several publish an action threshold rather than a range, so read your figure against the one printed on your own report. The same adult range applies at every age.
Is a transferrin saturation of 45% high?
It sits inside the 16 to 55% range above. It also sits above the 40% line at which UK labs investigate iron overload in women, and below the 50% line for men. What it means depends on your ferritin and your history, which a qualified clinician reads together.
Does a low transferrin saturation mean iron deficiency?
Not on its own. Royal United Hospitals Bath asks clinicians to request ferritin rather than transferrin saturation when investigating possible iron deficiency anaemia. A low saturation is a prompt to check ferritin, not an answer.
Should you stop iron tablets before the test?
Leaving that day's dose off gives a cleaner reading, because serum iron rises after a tablet and carries the saturation up with it. Take a morning sample. Do not stop anything a clinician has prescribed without asking them first.
How is transferrin saturation calculated?
It is worked out from your serum iron and your transferrin, which is why Royal United Hospitals Bath describes it as a calculated test. Nothing measures the percentage directly, so variation in either input moves the result.
What saturation suggests haemochromatosis?
Three NHS laboratories use the same threshold for further investigation: above 50% in men and above 40% in women. That is a trigger for looking further with ferritin and sometimes a genetic test, not a diagnosis in itself.
Related guides
Transferrin Saturation Blood Test UK
What the test measures, and when it is worth doing.
Iron Deficiency Blood Test
Ferritin, iron studies and what your results mean.
Optimal Ferritin Levels UK
Where the printed range ends and the useful target begins.
High Ferritin Levels UK
The other half of the iron overload picture.
Full Blood Count UK
The markers a clinician reads alongside your iron studies.
Energy and Fatigue Hub
Every tiredness marker guide in one place.