What happens when your iron is too low?

When iron stores fall, the body prioritizes essential functions. Keeping red blood cells working comes before supplying iron to muscles, the thyroid, or the brain. Early on, even at the iron depletion stage before anaemia develops, you may notice fatigue, reduced concentration, or hair shedding while your blood tests still look broadly normal. As depletion deepens, haemoglobin begins to drop and anaemia develops, which brings more pronounced symptoms: significant breathlessness, heart palpitations, and marked pallor. At the cellular level, iron deficiency impairs mitochondrial energy production and weakens immune function, which is why the effects reach well beyond tiredness.