The Link Between Iron, Thyroid and Mood

Most people only think about iron when a blood test shows anaemia, but low iron can also undermine metabolism and mood. Iron isn’t just about haemoglobin and energy — it’s a required cofactor for the enzymes that make and activate thyroid hormone, and it’s essential for building dopamine and serotonin. Small shortfalls can slow your metabolism and blunt motivation long before a standard blood count flags anaemia.

Where Your Iron lives

Most of your body’s iron lives in haemoglobin inside red blood cells — roughly 60–70% — with another 20–25% stored as ferritin and hemosiderin in the liver, spleen and bone marrow. Smaller pools sit in muscle as myoglobin and inside immune cells. Clinically we lean on serum ferritin to estimate stores because it reflects the readily available iron, but ferritin is also an acute‑phase reactant and rises with inflammation, infection or metabolic stress, so a “normal” or high ferritin can mask true tissue iron deficiency.

Iron can fall for a handful of predictable reasons: not enough bioavailable iron coming in, blood loss from heavy periods, or poor absorption when stomach acid is low or the gut lining is inflamed. It also drops when demand spikes — pregnancy, adolescence, hard training — or when inflammation or low thyroid output pushes up hepcidin, the hormone that blocks iron absorption and traps iron inside storage cells so it can’t circulate. Layer in everyday inhibitors like calcium, phytates and tannins from tea and coffee, and you’ve got a perfect setup for low‑iron symptoms long before haemoglobin ever drops.

Best Food Sources of Iron

Iron in food comes in two forms — heme (highly absorbable, from animal foods) and non‑heme (plant‑based, more easily blocked). For anyone dealing with low thyroid output or inflammation, the priority is simple: lean on heme‑rich foods and support absorption wherever you can.

Heme sources like grass‑fed red meat, liver, shellfish and dark poultry deliver iron in the form your body can use with minimal friction. They’re still affected by blockers like calcium and tannins, just far less than plant‑based iron.

Non‑heme sources — lentils, beans, spinach, pumpkin seeds, quinoa — still matter, but they need more support. Pair them with vitamin C, keep tea and coffee away from meals, and avoid calcium at the same time to give absorption a fighting chance.

You can also give meals a gentle iron lift by cooking in cast‑iron pans. Acidic or slow‑cooked dishes pick up small amounts of iron from the cookware — a simple, food‑first habit that supports overall intake whether the meal is plant‑based or includes meat.

Final Thoughts

When it comes to iron, a diet‑first approach gives you the most usable form, especially when you lean on heme‑rich foods and support plant sources with vitamin C. From there, focus on absorption optimisation — keep calcium, tannins, tea and coffee away from iron‑heavy meals, and make sure your gut and stomach acid aren’t working against you. Supplementation becomes the third step, not the first: use it only when symptoms, labs and context show that food alone isn’t enough, and always under the guidance of your practitioner. When you combine these three levers, iron stops being a confusing lab value and becomes a practical tool for steadier energy, clearer mood and stronger thyroid support.