Iron Blood Test (Serum Iron)

• Serum iron (measured): reported in µmol/L.

The following are not included in this test, though they are often requested with it as part of "iron studies":

• Ferritin: the iron storage protein.
• Transferrin or total iron-binding capacity (TIBC): how much iron-carrying capacity is in the blood.
• Transferrin saturation: a calculated percentage derived from serum iron and transferrin or TIBC.
• Full blood count: shows whether anaemia is present and what the red cells look like.

Most of the body's iron sits inside haemoglobin, the oxygen-carrying protein in red blood cells. Spare iron is stored as ferritin, mainly in the liver, spleen and bone marrow. Iron moves between these places attached to transferrin, and that circulating, transferrin-bound iron is what this test measures.

The body has no dedicated route for getting rid of iron, so it controls the amount it absorbs from food. A liver hormone called hepcidin does this. When stores are full, or when there is inflammation or infection, hepcidin rises, absorption falls and iron is held inside cells. That is why serum iron can be low during an illness even when stores are normal.

Serum iron behaves like a snapshot of traffic on a road. Lab Tests Online UK notes that it changes through the day and from day to day, and that iron from a meal or a tablet is absorbed quickly and can push the level up. Ferritin reflects stores, and the British Society of Gastroenterology describes it as the single most useful marker of iron deficiency anaemia. Even so, the British Society for Haematology points out that no single test can accurately assess iron balance, which is why results are read together.

Your report will show the laboratory's reference range, which may differ for men and women and between laboratories. Lab Tests Online UK states that serum iron is not a useful measure of iron status if used on its own, except when an iron overdose is suspected. The typical patterns it describes show why the other markers matter:

• Iron deficiency: low iron, low ferritin, high TIBC, low saturation.
• Inflammation or chronic illness: low iron and low TIBC, with normal or high ferritin.
• Haemochromatosis: high iron, high saturation, high ferritin, low TIBC.

A low serum iron alone may reflect true deficiency, but it can also follow a recent infection, inflammation, or a sample taken later in the day. A high result can follow an iron supplement or iron-rich meal in the previous hours, the contraceptive pill or oestrogen, or heavy alcohol use. In either case the sensible next step is usually a repeat morning sample with ferritin and transferrin saturation.

Do not start iron tablets on the basis of serum iron alone. Excess iron is harmful, and iron tablets must be kept away from children because overdose can be fatal. If you have symptoms of anaemia, or a family history of haemochromatosis, see your GP. Where a result needs medical attention, we will advise you to see your GP and, with your consent, can write to them.

Iron questions are common. The NHS describes iron deficiency anaemia as the most common type of anaemia, with heavy periods and pregnancy as very common causes, and bleeding from the stomach or bowel as another. At the other end of the scale, haemochromatosis, an inherited condition in which iron builds up slowly over years, is most common in people of northern European background, particularly those with Celtic ancestry.

Serum iron has a supporting role in answering both questions, alongside ferritin, transferrin saturation and a full blood count. Buying it on its own makes most sense when you already have some of those results, or when you want to repeat a serum iron result in the same way as before.

May find it useful: people who already have recent ferritin or full blood count results and want serum iron for completeness; people repeating a previous serum iron test; people asked by a clinician for this specific result.

A different route is better if:

• you want to know whether you are iron deficient: ferritin with a full blood count is more informative;
• you are a man, or a woman after the menopause, with symptoms of anaemia such as tiredness, breathlessness or palpitations: see your GP, as the cause needs investigating;
• you are pregnant: iron is checked as part of your antenatal care;
• a parent or sibling has haemochromatosis: the NHS advises speaking to your GP, even without symptoms.

Established: in men and in women after the menopause, iron deficiency anaemia is treated as a sign that needs investigation. The British Society of Gastroenterology recommends that gastroscopy and colonoscopy should generally be the first investigations for newly diagnosed iron deficiency anaemia in these groups, because bleeding from the gut is a common cause. A blood test result is the start of that process, not the end.

Established: in haemochromatosis, iron accumulates over decades. The NHS notes that symptoms usually begin between 30 and 60, and that if the condition is diagnosed and treated early it does not affect life expectancy.

Emerging research: iron's role in oxidative stress has made it a subject of ageing research. There is no evidence that adjusting a normal serum iron result changes how a person ages, and taking iron you do not need can cause harm.

• Book a morning appointment and have your sample taken before eating. Some laboratories ask for a 12-hour fast, with water only; we will confirm this when you book.
• If you take an over-the-counter iron supplement or multivitamin with iron, leave it out for the 24 hours before your sample. If your iron is prescribed, ask your prescriber before missing a dose.
• If you have had an infection or feverish illness recently, wait until you have recovered, as inflammation lowers serum iron.
• Tell us if you take the contraceptive pill or HRT, as oestrogen can raise serum iron.
• If you are repeating the test, keep the time of day and fasting state the same as before.

Choose how your sample is taken when you book. We confirm the collection option, any collection fee and the expected turnaround time before you book.

• Juvenology Clinic, Maidstone (82 King Street, Maidstone ME14 1BH): Available.
• Partner clinic near you, anywhere in the UK: Available on request. We confirm availability for your postcode before you book.
• Postal home finger-prick kit: Ask before ordering. We offer a home kit only where the laboratory confirms this test is suitable for a finger-prick sample.

Sample: Blood sample (serum)

Collection notes: Morning sample before eating recommended; the laboratory will confirm whether a 12-hour fast is required. Leave out over-the-counter iron supplements for 24 hours beforehand. A postal finger-prick kit is offered only where the laboratory confirms suitability, and morning collection timing still applies.

The price of this test covers laboratory analysis and the laboratory's results report. The report lists each result beside the laboratory's reference range.

Beyond the blood test: optional support, priced separately

• Personalised written interpretation report: £50
• General consultation: £50
• Results consultation (results discussion and follow-up advice): £100
• Personalised programme: from £150, after we assess whether a programme suits you

Consultations are with Marina, an NMC-registered nurse. She explains what your results show and how they relate to lifestyle. No prescription service is offered with these tests.

If a result suggests you need medical follow-up, we will recommend that you see your GP and, with your consent, can provide a letter to take with you. A blood test cannot rule out every condition. If you have symptoms, speak to your GP or NHS 111, and call 999 in an emergency.

Why is ferritin not included?

This product measures serum iron only. Ferritin, transferrin and transferrin saturation are separate measurements and are included in some of our wider panels.

Can this test diagnose iron deficiency anaemia?

No. Anaemia is shown by a full blood count, and iron deficiency is best assessed with ferritin. Serum iron alone cannot confirm or exclude either.

Do I need to fast?

A morning sample before breakfast is recommended because serum iron varies with time of day and recent meals. We will confirm whether a longer fast is needed.

My result is high. Do I have haemochromatosis?

Not necessarily. Recent iron intake, the contraceptive pill and other factors can raise serum iron. Haemochromatosis is assessed with ferritin, transferrin saturation and genetic testing through your GP.

Can I start iron tablets if my result is low?

Please do not rely on this result alone. A low serum iron can be caused by inflammation, and unnecessary iron can be harmful. Speak to your GP or pharmacist.

Is interpretation included?

The price covers analysis and the laboratory's report. A personalised written interpretation report (£50) or a results consultation (£100) can be added.

1. Iron tests. Lab Tests Online UK. https://labtestsonline.org.uk/tests/iron-tests
2. Snook J, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut, 2021;70(11):2030-2051. https://gut.bmj.com/content/70/11/2030
3. Good Practice Paper for the laboratory diagnosis of iron deficiency in adults (excluding pregnancy) and children. British Society for Haematology, 2021. https://b-s-h.org.uk/guidelines/guidelines/good-practice-paper-for-the-laboratory-diagnosis-of-iron-deficiency-in-adults-excluding-pregnancy-and-children
4. Iron deficiency anaemia. NHS. https://www.nhs.uk/conditions/iron-deficiency-anaemia/
5. Haemochromatosis. NHS. https://www.nhs.uk/conditions/haemochromatosis/