Iron
The most common nutritional deficiency in the world — but also one of the most dangerous to supplement without knowing your levels. Iron is essential for energy and oxygen transport, but excess iron is toxic. Test first, supplement second.
What is Iron and Why Does it Matter?
Iron is an essential mineral central to haemoglobin production — the protein in red blood cells that carries oxygen from the lungs to every cell in the body. Without adequate iron, red blood cells become smaller and fewer, delivering less oxygen. The result is iron-deficiency anaemia: fatigue, brain fog, shortness of breath, pale skin and reduced exercise performance.
Iron deficiency is the most common nutritional deficiency globally, affecting an estimated 2 billion people. Premenopausal women are most at risk due to menstrual blood loss. Athletes — particularly endurance athletes and female athletes — are a second major risk group. Vegans and vegetarians absorb non-haem iron (from plants) far less efficiently than haem iron from meat.
Always Test Before Supplementing Iron
Unlike most supplements, supplementing iron when you don't need it is genuinely harmful. Excess iron accumulates in organs and tissues, causing oxidative damage. It's also associated with increased cardiovascular risk. Always get a blood test (ferritin and haemoglobin) before starting iron supplements. Never take iron "just in case."
Ask your doctor for a full iron panel including: serum ferritin, serum iron, transferrin saturation and haemoglobin. Ferritin below 30 ng/mL suggests deficiency even if haemoglobin is normal — this "functional deficiency" causes fatigue and poor performance without full anaemia.
What Correcting Iron Deficiency Does
- Dramatically improves energy levels and reduces fatigue in deficient individuals
- Restores cognitive function — iron deficiency causes measurable impairment in memory and attention
- Improves exercise performance and VO2 max in anaemic athletes
- Reduces hair loss associated with low ferritin levels
- Improves mood — iron deficiency is associated with depression and anxiety
- Restores immune function — iron is essential for white blood cell production
How to Take Iron
Take iron on an empty stomach with vitamin C for maximum absorption. Never take with calcium, zinc or magnesium — they compete for the same transporters. Space them by at least 2 hours. Coffee and tea also inhibit iron absorption — avoid within 1 hour of dosing.
Critical Interactions to Know
Vitamin C — positive. Taking 500mg vitamin C with iron increases absorption by up to 67%. Always combine them.
Calcium — negative. Calcium strongly inhibits iron absorption. Never take together — space by at least 2 hours.
Zinc and magnesium — negative. Compete for the same intestinal transporters. Space by at least 2 hours.
Coffee and tea — negative. Tannins and polyphenols bind iron and reduce absorption by up to 60%. Avoid within 1 hour of taking iron.
Antibiotics (quinolones and tetracyclines) — iron binds to these antibiotics and reduces their effectiveness. Take iron 2 hours before or 4–6 hours after antibiotics.