Ferritin Change Calculator
Compare two ferritin test results with their dates and units to calculate the absolute change, percentage change and rate over time.
Result
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Ferritin trend
— ng/mL
- Percentage change
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- Rate per week
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- Rate per month
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- Time between tests
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Earlier ● Later ●
This compares numbers only. It does not diagnose deficiency or overload or tell you whether a trend is good.
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How to compare ferritin test results
This ferritin test calculator compares two results in ng/mL or mcg/L. Those units are numerically identical, which can be confusing when comparing lab reports. Enter the dates and the calculator gives the absolute change, percentage change and rates per week and month.
The plot uses commonly used typical adult ranges: roughly 24–336 ng/mL for men and 11–307 ng/mL for women. Every lab sets its own range, so the reference interval on your report wins. WHO uses ferritin below 15 mcg/L as indicating iron deficiency in adults; below 30 mcg/L is widely used as a practical cut-off when investigating deficiency because ferritin rises with inflammation.
Ferritin is an acute-phase reactant. Infection, inflammation, liver disease, recent alcohol and obesity can raise it independently of iron stores, so a rise is not automatically a gain in iron. Repletion is also slow: meaningful change is generally seen over months rather than weeks, so a short interval can show noise.
Absolute change = later − earlier; percentage change = (later − earlier) ÷ earlier × 100; rate/week = absolute change ÷ days × 7; rate/month = absolute change ÷ days × 30.4375 This tool computes and plots values only. It does not diagnose deficiency or overload, recommend supplements, doses or transfusions, or tell you whether a trend is good. Iron supplements are a leading cause of poisoning deaths in young children and belong out of reach. For related calculations, see /tools/ferritin-unit-converter and /tools/iron-level-chart.
NIH Office of Dietary Supplements: Iron fact sheet for health professionals ↗
Ferritin change calculator FAQ
Are ng/mL and mcg/L the same for ferritin?
Yes. Ferritin values reported in ng/mL and mcg/L are numerically identical, so no conversion is needed.
Why can ferritin rise without more stored iron?
Ferritin is an acute-phase reactant. Infection, inflammation, liver disease, recent alcohol and obesity can raise it independently of iron stores.
Which reference range should I use?
Use the reference interval printed on your own lab report. The ranges shown here are typical adult ranges, not a diagnosis.
Why does the calculator require different dates?
Rates need a non-zero time interval. The later date must come after the earlier date.
Does this result tell me whether my trend is good?
No. It only performs the comparison and plot. Discuss the results and your lab's reference range with a qualified clinician.