Ferritin Blood Test (UK): What It Measures, Reference Ranges & How to Prepare

A ferritin blood test helps estimate how much iron your body has in reserve. It can identify depleted stores before haemoglobin becomes low, but the number is most useful when read alongside the laboratory range, the full blood count, symptoms and the reason the test was requested.

This guide explains what ferritin measures, why ranges differ, how inflammation can affect the result and what to expect before and after a UK blood test.

For the wider food and absorption picture, see our guide to low ferritin and rebuilding iron stores.

What does a ferritin blood test measure?

Ferritin is a protein that stores iron inside cells. A small amount circulates in the blood, and measuring it provides a useful estimate of the body's iron reserves. This is different from serum iron, which reflects iron circulating at the time of the test and can vary more readily.

The British Society of Gastroenterology guideline describes ferritin as the most specific marker of iron deficiency when inflammation is absent. It considers levels below 15 micrograms per litre indicative of absent stores and levels below 30 micrograms per litre generally indicative of low stores.

Why is ferritin different from haemoglobin?

Ferritin reflects reserves; haemoglobin is the oxygen-carrying protein inside red blood cells. Stores can decline before haemoglobin falls below the laboratory threshold for anaemia. That is why a normal full blood count does not always answer the question of whether iron stores are low.

The tests commonly considered around iron status each add something different:

• Ferritin helps estimate stored iron.
• Haemoglobin helps identify anaemia in the relevant laboratory and population context.
• Transferrin saturation helps show how much of the iron-transport protein is carrying iron.
• Inflammatory markers may help when ferritin appears inconsistent with the wider clinical picture.

Our guides to what ferritin is and ferritin reference ranges explore these distinctions in more detail.

What do ferritin reference ranges mean in the UK?

There is no single reference interval used by every UK laboratory. Methods, equipment, local populations and reporting policies differ, so the range printed beside your own result is the correct starting point.

Clinical thresholds and laboratory reference intervals are not quite the same thing. The guideline thresholds above help clinicians recognise depleted stores, while the laboratory range shows how that service reports results. The NICE Clinical Knowledge Summary on iron-deficiency anaemia provides the current UK primary-care pathway for assessment and management.

A result should not be converted into a universal “optimal ferritin” target from an online chart. Your age, sex, pregnancy status, symptoms, inflammation, bleeding history and other blood results can all change what needs to happen next.

Why can inflammation affect ferritin?

Ferritin is also an acute-phase protein, which means its concentration may rise during inflammation or infection. A result that appears normal or high can therefore be harder to interpret when the body is dealing with an inflammatory process.

The WHO guidance on ferritin concentrations discusses adjustment and interpretation in settings where infection or inflammation is common. In individual care, clinicians may consider symptoms, C-reactive protein, transferrin saturation and the wider medical picture rather than relying on ferritin alone.

Hepcidin helps explain part of the biology. This liver-produced hormone controls ferroportin, the protein that releases iron from intestinal cells and recycling cells into the bloodstream. A review of iron metabolism describes how iron status, red-cell production and inflammation influence this system.

Why might a GP request ferritin?

Ferritin may be requested when symptoms, diet, bleeding, pregnancy, donation history or another test raises a question about iron stores. Common reasons include:

• persistent tiredness or reduced exercise tolerance;
• heavy menstrual bleeding;
• pregnancy or planning pregnancy;
• a restrictive or low-iron diet;
• blood donation;
• possible gastrointestinal blood loss or impaired absorption;
• monitoring after an earlier low result or treatment.

These features are not specific to iron deficiency. Ferritin helps add evidence to the investigation rather than diagnosing the cause from symptoms alone.

What happens during the test?

A healthcare professional takes a small sample of blood, usually from a vein in your arm. The appointment itself is generally brief. The NHS blood-test guide explains the usual process, possible bruising and how results are returned.

Do you need to fast?

Ferritin on its own does not usually require fasting. Your appointment may include other tests with different instructions, so follow the information from the GP surgery, clinic or laboratory.

Should you stop supplements?

Do not stop prescribed iron or another medicine simply because a blood test is booked. Tell the arranging service what you take and follow its instructions. The correct approach depends on whether the test is a baseline investigation, a treatment check or part of a wider panel.

How long do results take?

Timing varies by laboratory, urgency and the other tests ordered. Ask the arranging service when and how the result will be communicated rather than relying on a universal turnaround time.

How should you read the result?

Begin with the value, unit and reference interval printed on the report. Then consider why the test was requested and whether haemoglobin, mean cell volume, transferrin saturation or inflammatory markers were measured at the same time.

• Low ferritin: usually supports depleted iron stores and prompts consideration of the cause.
• Ferritin within range: may be reassuring, but inflammation and the wider blood picture still matter.
• High ferritin: has several possible explanations and does not automatically mean iron overload.

The NHS iron-deficiency anaemia guidance explains how blood loss, pregnancy and diet can contribute and why unclear cases may need further investigation.

What can affect iron intake and absorption?

Iron from animal foods and non-haem iron from plant foods are absorbed differently. Vitamin C can help with non-haem iron absorption within a meal, while tea and coffee consumed with the meal can reduce it. The size of these effects varies with the food, meal and person.

The SACN Iron and Health report supports a varied iron-containing diet rather than trying to calculate a fixed absorption percentage for every meal. Practical habits include:

• eat reliable iron sources regularly;
• combine plant iron with fruit or vegetables when convenient;
• consider having tea or coffee between meals when intake is a concern;
• follow medicine instructions separately from general food advice.

The NHS iron page provides UK intake guidance and food sources. Our guides to haem and non-haem iron and improving iron absorption turn the principles into everyday choices.

Where does Spirulina fit?

Spirulina can contribute non-haem iron, but the amount depends on the exact product and serving. Use the product's own nutrition declaration rather than a generic value from another Spirulina sample.

ALPHYCA approaches this area differently from brands that begin with generic ingredients at the blending stage. It cultivates Spirulina in its own controlled photobioreactor system, and uses in-house biomass-modification expertise to develop iron-enriched Spirulina for targeted formulas.

Algoglobin combines iron-enriched Spirulina and iron bisglycinate with vitamin C, active folate, vitamin B12, zinc and copper. It gives readers who have already discussed suitability with a professional a focused, vegetarian supplement route built around normal blood formation and energy-support nutrient functions.

The Bioactive Iron Energy protocol is the broader option. It places Algoglobin at the centre and adds an ALPHYCA Spirulina format as the nutritional foundation. The useful distinction is simple: Algoglobin is the focused product; the protocol organises it within a more complete daily routine.

This integrated approach reflects how ALPHYCA connects Spirulina cultivation, biomass development and formulation within one system. It explains how the company's iron-support products are developed while remaining separate from clinical investigation and treatment decisions.

What should happen after a low result?

A low result starts a conversation about cause and next steps. Food may support intake, while confirmed deficiency may also require oral iron and follow-up testing. Heavy periods, pregnancy, donation, gastrointestinal symptoms, previous surgery and persistent inflammation can all influence the plan.

Do not chase a higher number without understanding why stores fell. The goal is to restore iron appropriately and address ongoing loss or absorption problems where present.

When should you seek medical advice?

Contact your GP when the result is below the laboratory range, symptoms persist, periods are heavy, you are pregnant or planning pregnancy, or treatment is not working as expected. Unexplained iron deficiency in adult men and postmenopausal women particularly requires investigation.

Seek prompt advice for chest pain, fainting, marked breathlessness, palpitations, blood in the stool, black tar-like stool before taking iron, severe weakness or other worrying changes.

FAQ

What does a ferritin blood test measure?

It measures ferritin in the blood to help estimate stored iron. A low value supports depleted stores, while inflammation can make a normal or high value harder to interpret.

What is a normal ferritin level in the UK?

There is no single range used by every UK laboratory. Read the interval printed beside your result and discuss it in the context of symptoms, haemoglobin and possible inflammation.

Do I need to fast before a ferritin blood test?

Usually not for ferritin alone. Follow the appointment instructions because other tests taken at the same time may require preparation.

How long do ferritin results take?

Turnaround varies by laboratory and urgency. The arranging service can tell you when and how your results will be available.

Where does Algoglobin fit after testing?

Algoglobin is ALPHYCA's targeted vegetarian iron-support formula. Consider it only after understanding the result, its likely cause and whether a food supplement is appropriate alongside any recommended treatment.

Key takeaways

• Ferritin helps estimate iron stores and may become low before haemoglobin.
• Use the range printed by the laboratory rather than a universal online “optimal” range.
• Inflammation can raise ferritin and change how the result is interpreted.
• Ferritin usually needs no special preparation, but follow the instructions for the complete blood-test appointment.
• A low result should lead to consideration of intake, blood loss, requirements, absorption and appropriate treatment.
• Algoglobin and Bioactive Iron Energy provide focused-product and structured-protocol ways to explore ALPHYCA's iron-support work.

Final thought

A ferritin result is most useful when it turns a vague concern into a sensible next step. Read the number in context, understand the likely cause and then choose food, treatment or supplemental support for a clear reason—not simply to chase a laboratory target.