What makes ferritin go up?

Qassi Gaba · 5 November 2026 · 4 min read

Ferritin goes up for more than one reason, and that is the whole difficulty with the number. It rises when your iron stores rise, but it also rises during infection or inflammation, and it rises sharply for a while after an iron infusion. A single ferritin result cannot tell you which of these is happening. That is a question for whoever ordered the test, with the rest of your bloodwork in front of them.

It is not only an iron number

Ferritin is the protein your body uses to store iron, which is why it gets ordered when someone is checking iron status. But ferritin is also what is called an acute phase reactant: a protein the body produces more of during inflammation, independent of how much iron is actually in storage. A review in Metallomics on this point makes clear that ferritin released into the blood during illness or tissue damage is largely a byproduct of cells leaking their contents, not a tidy readout of iron reserves.

That matters for anyone with an autoimmune thyroid condition, because Hashimoto's thyroiditis is itself an ongoing immune process. A ferritin result drawn during a flare, a cold, or any other inflammatory stretch can sit higher than it would on a quiet week, for reasons that have nothing to do with iron.

Infection and inflammation push it up quickly

Ferritin does rise with inflammation, often within days. A chest infection, a flare of joint inflammation, even a minor injury can lift ferritin temporarily. It tends to come back down once whatever caused it resolves. If a lab panel is drawn while you happen to be unwell, that context is worth mentioning to whoever is reading the result, because ferritin cannot distinguish "I was fighting something off" from "my stores are high."

This is also why ferritin is rarely read on its own. A standard blood test ordering a ferritin panel usually includes other markers alongside it, iron and transferrin saturation among them, so that an inflamed ferritin reading does not get mistaken for an iron-loaded one.

An iron infusion raises it, and keeps it up for a while

If you have recently had an intravenous iron infusion, ferritin rising afterward is expected and is not a separate finding to puzzle over. Infusions like ferric carboxymaltose deliver iron directly into the bloodstream in a form the body processes gradually, and the prescribing information for products in this class notes that serum ferritin increases following administration and can stay elevated for a period afterward before settling.

How long that period lasts varies by product and dose, which is exactly why repeat ferritin testing after an infusion is usually timed deliberately rather than drawn whenever happens to be convenient. If a test was taken too soon after an infusion, that is useful context for your doctor, not something to interpret yourself.

Iron deficiency and thyroid testing often travel together

Doctors investigating hypothyroidism frequently check iron status alongside thyroid function, partly because fatigue, hair changes and poor concentration can come from either, and the two are not mutually exclusive. NICE's clinical summary on hypothyroidism reflects this overlap in the kind of workup it describes.

That is also why there is no single answer to what pushed a ferritin result up. A slow rise over months, with nothing else changing, points toward iron stores genuinely building up. A sharp rise that coincides with being unwell points toward inflammation. A rise that starts right after an infusion appointment points toward the infusion. The pattern over time tells you more than any single value, which is true of thyroid antibodies and TSH as well, and is why MedlinePlus's overview of thyroid disease treats a one-off result as the start of a conversation rather than the end of one.

What this is not

This is not a guide to raising your ferritin. Whether a ferritin result calls for dietary changes, a supplement, an infusion, or nothing at all depends on the full picture: your iron studies, your symptoms, what else was happening in your body on the day of the draw, and what your doctor is actually trying to rule in or out. None of that is something a blog post can assess from outside, and guessing at it from a number alone is a good way to act on the wrong cause.

Where this touches Haloscan

Haloscan lets you log an iron infusion or a recent illness alongside your lab results, the same way it logs a missed dose or a new symptom. When a ferritin value jumps on the report you bring to an appointment, that context sits right next to it, instead of your doctor having to ask you to remember what was going on that week.