Iron deficiency affects over 2 billion people worldwide — and the majority don't know they have it. The problem is the symptom overlap: fatigue, difficulty concentrating, and reduced exercise tolerance are easy to attribute to stress, poor sleep, or simply "being busy." Yet in many cases, the underlying cause is a depleted ferritin store that a single blood test would reveal.
Iron's Role in Energy Production
Iron is the central component of haemoglobin — the protein in red blood cells that binds and transports oxygen from your lungs to every tissue in your body. Without adequate iron, oxygen delivery is impaired. Your muscles, brain, and every other organ receives less oxygen, leading to the constellation of symptoms that define iron deficiency.
Iron also plays a critical role in mitochondrial function — the cellular machinery that produces ATP (energy). Even before anaemia develops, low iron impairs mitochondrial efficiency and reduces the capacity for sustained physical or cognitive effort.
The Ferritin-First Approach
Standard haemoglobin testing misses early iron deficiency. Your body will sacrifice ferritin (stored iron) before allowing haemoglobin to fall — meaning you can have severely depleted stores and feel terrible while your haemoglobin appears normal. Testing ferritin directly is essential. Optimal ferritin for energy and wellbeing is generally considered 70–150 µg/L — not just "above the lab's lower reference limit" of 15–20 µg/L.
Signs of Iron Deficiency to Watch For
- Persistent fatigue unimproved by sleep or rest
- Exercise intolerance — earlier than expected breathlessness or muscle fatigue
- Brain fog and difficulty maintaining concentration
- Brittle or spoon-shaped nails
- Hair shedding — often noticed as increased loss in the shower
- Pale inner eyelids or pale complexion
- Cravings for ice, clay, or other non-food items (pica)
- Restless legs syndrome — particularly at night
