Ferritin and Iron Status Interpreter

Interpret serum ferritin alongside CRP and transferrin saturation to distinguish true iron deficiency from inflammation-masked deficiency and from iron overload.

🩸 Lab Value📐 Interpretation combines ferritin, CRP, and TSAT patterns🏥 Health

Ferritin (ng/mL)

CRP (mg/L, optional)

Population

Transferrin saturation (%, optional)

Please enter valid values.

Formula & Reference

Variable	Symbol	Formula	Units
Ferritin and Iron Status Interpreter	—	Interpretation combines ferritin, CRP, and TSAT patterns	ng/mL

Step-by-Step Examples

Example 1

Straightforward Deficiency

Ferritin 8 ng/mL, CRP 2 mg/L, TSAT 7%.

Ferritin below 15 ng/mL
CRP normal, so no inflammatory masking
Low TSAT confirms the picture

✓ Iron deficiency — clear pattern

Example 2

Masked by Inflammation

Ferritin 85 ng/mL, CRP 40 mg/L, TSAT 9% in rheumatoid arthritis.

Ferritin looks normal by the standard 30 ng/mL threshold
CRP 40 mg/L indicates active inflammation
In inflammation, a 100 ng/mL threshold is often applied
Low TSAT alongside this points to genuine deficiency

✓ Likely iron deficiency masked by inflammation

Example 3

Possible Overload

Ferritin 950 ng/mL, CRP 3 mg/L, TSAT 68%.

Markedly elevated ferritin
CRP normal, so inflammation is not the explanation
TSAT 68% is well above the overload threshold

✓ Pattern warrants evaluation for iron overload

Real-World Applications

💉

Anaemia Evaluation

Ferritin is the single most useful test for iron deficiency, but its interpretation depends heavily on inflammatory context.

🏃

Athlete Monitoring

Endurance athletes are screened for low ferritin, since depleted stores impair performance well before anaemia develops.

🤰

Pregnancy Care

Iron demands rise sharply in pregnancy, and ferritin thresholds are interpreted differently across trimesters.

🧬

Haemochromatosis Follow-Up

Serial ferritin measurement tracks iron burden and guides the frequency of therapeutic phlebotomy.

Common Mistakes to Avoid

⚠️

Using one ferritin threshold for everyone

The cutoff shifts with context. Around 15 ng/mL is highly specific for deficiency, 30 ng/mL is a common practical threshold, and 100 ng/mL is often used when inflammation is present.

⚠️

Forgetting ferritin is an acute phase reactant

Infection, inflammation, liver disease, and malignancy all raise ferritin independently of iron stores, which can hide a genuine deficiency behind a normal-looking number.

⚠️

Starting iron supplements without a diagnosis

Iron supplementation without confirmed deficiency causes gastrointestinal side effects and, in undiagnosed haemochromatosis, can be actively harmful.

Frequently Asked Questions

What is ferritin? ▾

An intracellular iron storage protein whose serum concentration usually reflects total body iron stores — unless inflammation is distorting it.

What ferritin level indicates iron deficiency? ▾

Below 15 ng/mL is highly specific, and many clinicians treat below 30 ng/mL as consistent with deficiency. With inflammation present, thresholds up to 100 ng/mL are used.

Can I have iron deficiency with normal ferritin? ▾

Yes. Inflammation raises ferritin independently of iron stores, so a normal value alongside a low transferrin saturation and elevated CRP can still mean deficiency.

What causes high ferritin? ▾

Iron overload, but far more often inflammation, infection, liver disease, heavy alcohol use, metabolic syndrome, or malignancy.

Should I take iron supplements if ferritin is low? ▾

Discuss it with your clinician first. Low ferritin needs a cause identified — particularly in adults, where gastrointestinal blood loss must be considered.