Iron
Iron Studies Blood Test UK: The Five Numbers, and What to Do When They Disagree
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed September 20267 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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Iron studies is one blood request that returns five results: serum iron, ferritin, transferrin, transferrin saturation and total iron binding capacity. Ferritin is the main one. The British Society of Gastroenterology puts most UK lab floors for it between 15 and 30 micrograms per litre.
Not sure which markers you need? Build your test →Your report says IRON STUDIES and then lists five things. One has an H beside it. Another has an L. Nothing explains why a single request came back with five answers, or which of them you are supposed to care about.
Here is the short version. Iron moves around your body in a system, and no single measurement sees all of it. The five numbers look at that system from different angles. Read together they usually agree. When they do not, the disagreement is the finding.
1. What is an iron studies blood test?
It is one request, not one test. A UK lab takes your sample and runs a small group of related measurements, then prints them under a single heading. You may also see it called an iron panel or iron profile.
For the serum iron line on its own, and what it means at your age, see iron levels by age.
The reason for the grouping is simple. Iron in your blood is being carried, and iron in your tissues is being stored. Those are two different questions, and a clinician usually wants both.
2. What does each of the five numbers mean?
Each row below is one line on your report, in plain words.
| Marker | What it actually is | A low result suggests |
|---|---|---|
| Ferritin | The protein that holds iron in reserve, so it shows how much you have banked | Your stores are running down |
| Serum iron | The iron circulating in your blood at the moment of the sample | Little on its own, because it swings through the day |
| Transferrin | The delivery protein that carries iron round the body | Poor nutrition, inflammation or liver trouble, not low iron |
| Transferrin saturation | How full those delivery vans are, as a percentage | Supply is not keeping up with demand |
| TIBC | Total iron binding capacity, meaning how much iron your blood could carry if full | Usually the same picture as a low transferrin |
Two of those move as a pair. Transferrin and TIBC measure nearly the same thing, so your lab may print one, the other, or both. Our TIBC guide covers why the pair usually rises when iron falls.
The BSG guideline lists the pattern to look for in one line. The serum markers of iron deficiency, it says, include low ferritin, low transferrin saturation, low iron and raised total iron binding capacity. That is the classic set. Four numbers pointing one way.
3. What ferritin level counts as low in the UK?
Lower than most people expect, and labs do not all draw the line in the same place. The BSG guideline sets out the numbers behind that spread.
- Under 15 micrograms per litre means iron stores are absent.
- Under 30 generally means stores are low.
- So most UK lab floors sit somewhere between 15 and 30.
- A cut-off of 45 has been proposed as the better trade-off in practice.
- Above 150, absolute iron deficiency is unlikely.
Look at what that does to a result of 22. It is inside some UK reference ranges and under others. Your own lab range is the one that matters, and the question of an optimal ferritin is a separate one from the question of a normal one.
One more thing that catches people out. You can be low on iron without being anaemic, because stores empty before the blood count changes. We cover that gap in low ferritin with a normal haemoglobin.
4. Why can ferritin look normal when iron is low?
Because ferritin has a second job. It rises when your body is inflamed, which happens with infection, injury and many long-term conditions. A rise from inflammation can cancel out a fall from low stores, and the number lands in the normal band.
This is the single best reason to look at the other four. The guideline that UK gastroenterologists work to says so plainly.
“Serum ferritin is the single most useful marker of IDA, but other blood tests (eg, transferrin saturation) can be helpful if a false-normal ferritin is suspected.”
British Society of Gastroenterology, Gut 2021 (IDA means iron deficiency anaemia)
Transferrin saturation is the marker that catches it. The same guideline says a saturation under 20% indicates iron restriction, meaning your body cannot get hold of enough iron for the job. So a mid-range ferritin next to a saturation of 12% is worth a conversation, even though nothing was flagged.
The reverse happens too. A raised CRP, the standard marker of inflammation, sitting beside a comfortable ferritin tells a clinician to be careful about reading that ferritin at face value.
5. What does a high iron studies result point at?
It depends which number is high. A raised ferritin on its own is common and often reflects inflammation, alcohol or a fatty liver rather than too much iron.
A high ferritin together with a high transferrin saturation is a different pattern. That pairing is the one clinicians look at when considering iron overload, and it is why haemochromatosis gets investigated with the set rather than with ferritin alone. Our high ferritin guide walks through the usual causes.
Two things worth saying plainly. A blood test measures markers and gives you something concrete to take to a GP. It does not diagnose any condition, and one marker outside its range does not on its own mean something is medically wrong.
6. Which blood test includes iron studies?
Helvy measures the full set in one panel. Vitamins & Minerals carries iron, ferritin, transferrin, transferrin saturation and TIBC, plus vitamin B12, folate, vitamin D and magnesium. It is a home finger-prick kit, processed by a UKAS-accredited UK lab.
The extra four matter more than they look. Low iron, low B12 and low folate all cause tiredness, and they can happen together, so a single low ferritin is rarely the whole story.
Two honest limits. This panel does not include a full blood count, so it shows your iron position rather than whether you are anaemic. And if your GP is already investigating, the NHS route is the right one. The NHS says a GP will usually start with a full blood count to check whether your red cell count is normal.
If you are not sure which panel fits, the build-my-test tool walks you through it in about a minute. The energy and fatigue hub collects the rest of these guides, and our full blood count guide explains the test that sits beside iron studies on most NHS requests.
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See all five iron numbers together
Helvy's Vitamins & Minerals test reports iron, ferritin, transferrin, transferrin saturation and TIBC beside your B12, folate, vitamin D and magnesium, read against your own lab ranges, so a flagged number never sits there unexplained. Ask your blood.
Frequently asked questions
What is included in an iron studies blood test?
Serum iron, ferritin, transferrin, transferrin saturation and total iron binding capacity. Some labs print four of the five, because transferrin and TIBC measure nearly the same thing.
Which iron number matters most?
Ferritin. The British Society of Gastroenterology calls it the single most useful marker of iron deficiency anaemia, and adds that other tests help when a false-normal ferritin is suspected.
Is a ferritin of 20 low?
It sits in the grey band. Under 15 means stores are absent and under 30 generally means they are low, so most UK lab floors fall between those two figures. Check the range printed on your own report.
What does a low transferrin saturation mean?
That your blood is carrying less iron than the system is asking for. The BSG guideline describes a saturation below 20% as indicating iron restriction, and it is the marker that catches deficiency hidden by inflammation.
Do I need to fast for an iron studies test?
Serum iron is higher in the morning and moves after meals and after iron tablets, so labs often ask for a morning sample. Follow the instruction on your own request form or kit. Our fasting guide covers the general rules.
Which Helvy test measures iron studies?
Vitamins & Minerals. It carries iron, ferritin, transferrin, transferrin saturation and TIBC with vitamin B12, folate, vitamin D and magnesium, from a home finger-prick sample.