Optimal Ranges
Clinical (NHS) Range
10-30 µmol/L (serum iron)
µmol/L / %
Performance-Optimised Range
15-25 µmol/L (serum iron), 20-45% transferrin sat.
µmol/L / %
The clinical range defines what is considered medically “normal” — broad enough to cover 95% of the population. The performance range reflects where research and clinical experience suggest most people feel and function at their best.
Why It Matters
Why Iron matters for performance
Iron deficiency is the most common nutritional deficiency in the UK, affecting an estimated 3% of men and up to 25% of women of reproductive age according to the NHS. For active people, iron demands are significantly higher — endurance training, heavy sweating, and even foot-strike haemolysis from running can deplete iron stores faster than diet replaces them. Low iron doesn't just mean anaemia: even subclinical deficiency impairs oxygen delivery to muscles, slows recovery, and causes persistent fatigue and brain fog that many people attribute to stress or poor sleep. A full iron panel catches problems that a standalone ferritin test can miss, such as iron-loading disorders or poor absorption despite adequate intake.
Symptoms
Signs your levels may be off
Low / Deficiency
- Persistent fatigue and low energy
- Breathlessness during exercise
- Pale skin, nails, and inner eyelids
- Frequent headaches
- Difficulty concentrating and brain fog
- Restless legs, especially at night
- Craving non-food items (pica) — ice, dirt
- Slow recovery from workouts
High / Excess
- Joint pain and stiffness
- Abdominal pain and bloating
- Bronze or grey skin discolouration
- Chronic fatigue (paradoxically similar to deficiency)
- Liver damage (haemochromatosis)
- Heart rhythm problems
Dietary Sources
Foods that support Iron levels
Supplementation
Evidence-based supplementation
Iron bisglycinate is the gold standard supplemental form — absorbed 2-4x better than ferrous sulphate with far fewer gut side effects. Typical dose: 15-25 mg elemental iron daily when deficiency is confirmed by blood testing. Always take with 200 mg vitamin C (or alongside vitamin C-rich foods like citrus or peppers) to boost absorption by up to 67%. Avoid taking iron within 2 hours of calcium supplements, tea, coffee, or dairy, as these inhibit absorption. Never supplement iron without testing first — excess iron is toxic and cannot be easily excreted. The hereditary condition haemochromatosis (affecting ~1 in 200 people of Northern European descent) causes dangerous iron overload. Retest after 90 days to confirm response and adjust dosing.
Research
Key study
Iron deficiency anaemia: assessment, prevention and control — a guide for programme managers
World Health Organization
WHO Technical Report Series (2001)
DOI: 10.1016/S0140-6736(15)60865-0Related Biomarkers
Related Guides
Test your Iron levels
Iron is included in the Helvy 50+ biomarker panel. Get your results in 5 days with a personalised protocol.
Order Your TestThis content is for educational purposes only and does not constitute medical advice. Your data suggests areas for optimisation, but any concerns should be discussed with a qualified healthcare professional. If your results flag values outside safe ranges, we recommend consulting your GP.