Iron circulates as hemoglobin in red blood cells and as myoglobin in muscle, but roughly 25% of your body’s iron is tucked away in storage, held primarily in the liver, spleen, bone marrow, and skeletal muscle. Ferttin blood testing measures reserve.
Ferritin is a metabolic and inflammatory signal.
Low ferritin may indicate iron deficiency before anemia appears on standard lab work. Ferrtin levels below 30 make the diagnosis of anemia. And low iron stores aren’t subtle: signs can include not only fatigue and brittle nails, but also restless legs syndrome, increased hair shedding, cold intolerance, brain fog, and even shortness of breath on exertion.
Emerging data suggest that ferritin plays a complex role in insulin resistance, cardiovascular risk, and bone metabolism. Low ferritin can impair physical function, cause brain fog, and worsen chronic fatigue, while high ferritin is linked to inflammation, fatty liver disease, and accelerated bone loss. In fact, elevated ferritin levels have been associated with osteoporotic fractures and poorer bone mineral density outcomes.
Ferritin Signals Acute Physiology Stress
Ferritin also behaves as a acute phase reactant, increasing with inflammation, infection, or immune dysfunction. This means high ferritin doesn’t always equal high iron; sometimes, it’s a red flag for a body under chronic stress.
A fascinating insight: some medications not obviously tied to iron metabolism still impact ferritin. For example, risedronate, an osteoporosis drug, has been shown to lower ferritin levels, which may partly explain its protective effects—not just on bone, but also on cardiovascular health and even all-cause mortality in postmenopausal women.
Iron needs to be in balance
We lose about 1-2 mg of iron a day in sweat, those who do hot yoga or hot Pilates might lose a bit more.
Too little iron leads to functional impairment. Too much can harm the liver, bone, and even sexual health. For anyone dealing with persistent symptoms that don’t fit a tidy diagnosis, checking a ferritin level might offer a missing clue.
Key Takeaways:
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Ferritin reflects your iron storage, not just anemia.
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Low ferritin may cause fatigue, restless legs, cold hands/feet, or thinning hair—even if hemoglobin is normal.
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High ferritin may indicate inflammation, insulin resistance, or early liver disease.
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Certain medications may influence ferritin—and that effect may be beneficial.
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Optimal ferritin is a range, not just “above normal.”
If you’re struggling with chronic fatigue, vague symptoms, or bone health issues, talk to your doctor about testing your ferritin. A simple lab might clarify what your body’s been trying to tell you.
