Ferritin

Ferritin is the protein your body stores iron inside. Measuring it in blood gives an indirect but reliable read on the size of your iron reserves, which is why it is used ahead of serum iron for assessing iron status. Serum iron moves with the last meal; ferritin moves with the stores.

Iron is needed to build haemoglobin, which carries oxygen, and it also sits in the enzymes that run cellular energy production. Low stores show up as fatigue and reduced exercise capacity before they show up as anaemia, because the body will drain the bank before it lets haemoglobin fall.

Below 15 ng/mL indicates depleted iron stores. Symptoms often reported at low ferritin include fatigue, poor exercise tolerance, cold intolerance, hair shedding and reduced concentration.

The cause matters more than the number. Low ferritin comes from inadequate intake, poor absorption, or ongoing loss. In menstruating people, monthly loss is the common driver. Blood donation, endurance training and gastrointestinal loss are others.

Iron supplementation without knowing the cause is worth avoiding, and a persistently low result is a reason to talk to your practitioner rather than to start high-dose iron on your own.

Between 15 and 270 ng/mL your stores sit inside the reference range for this panel.

Ferritin has a wide reference range because normal stores vary a great deal between individuals. A result at the bottom of the range with symptoms is worth more attention than the same number without them.

Above 270 ng/mL has two very different explanations, and separating them is the whole task.

Ferritin is an acute phase reactant, so it rises with inflammation, infection, liver conditions and heavy alcohol intake regardless of iron status. A high ferritin during or shortly after an infection frequently reflects the inflammation rather than the iron.

The other explanation is genuine iron loading, including hereditary haemochromatosis. Distinguishing the two needs transferrin saturation and often CRP alongside the ferritin, which is a conversation for your practitioner rather than something this number settles alone.

Two Western patterns pull in opposite directions. Low intake of iron-rich foods, combined with high intake of tea, coffee and calcium around meals, suppresses absorption and depletes stores.

At the same time, chronic low-grade inflammation from a Western dietary pattern raises ferritin independently of iron. That combination produces the awkward case of someone with genuinely low iron stores and a ferritin reading that looks unremarkable.

Haem iron from red meat, liver, and shellfish absorbs several times better than non-haem iron from plants.

Non-haem sources include legumes, tofu, pumpkin seeds and dark leafy greens. Pair them with a vitamin C source in the same meal, which meaningfully raises absorption.

Move tea, coffee and calcium supplements away from iron-containing meals. Both suppress non-haem absorption when taken together.

Iron bisglycinate is better tolerated than ferrous sulphate at equivalent doses and causes less digestive upset.

Alternate-day dosing absorbs better than daily dosing, because a dose raises hepcidin for roughly 24 hours and blunts the next one.

Take iron away from coffee, tea, calcium and zinc. Do not supplement iron on the basis of symptoms alone; confirm with a test first, since loading iron when stores are already adequate carries its own risk.