Optimal Ranges
Clinical (NHS) Range
Hb: 130–170 g/L (men)
g/L (haemoglobin)
Performance-Optimised Range
Hb: 145–165 g/L (men)
g/L (haemoglobin)
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 FBC matters for performance
For active men, the FBC is the single most informative baseline test. Haemoglobin directly determines your VO₂ max ceiling — research shows total haemoglobin mass is roughly 15% higher in endurance-trained athletes than untrained individuals, and even a small drop from iron-deficiency anaemia can slash exercise capacity before you notice symptoms. Your white cell differential flags overtraining: a persistently low lymphocyte count or inverted neutrophil-to-lymphocyte ratio can signal immune suppression from excessive training load. MCV and MCH catch early B12 or folate deficiency (macrocytic anaemia) or iron deficiency (microcytic anaemia) months before you feel fatigued — the red cell indices shift before haemoglobin drops. Platelet count matters for recovery: low platelets impair wound healing and bruising, while a reactive high count can follow intense inflammation.
Symptoms
Signs your levels may be off
Low / Deficiency
- Persistent fatigue and low energy despite adequate sleep
- Breathlessness during exercise at usual intensity
- Pale skin, nail beds, or inner eyelids
- Dizziness or light-headedness on standing
- Unusually slow recovery between training sessions
- Frequent colds or infections (low WBC)
- Easy bruising or prolonged bleeding from cuts (low platelets)
High / Excess
- Headaches and flushed complexion (high Hb / polycythaemia)
- Blurred vision or dizziness (high haematocrit thickens blood)
- Increased clotting risk (elevated platelets or haematocrit)
- Joint pain or itching after hot showers (polycythaemia vera)
- Unexplained weight loss with high WBC (investigate further)
Dietary Sources
Foods that support FBC levels
Supplementation
Evidence-based supplementation
FBC abnormalities are treated by addressing the root cause, not by supplementing blindly. Low haemoglobin with low MCV suggests iron deficiency — ferrous bisglycinate (25–50mg elemental iron daily) is better tolerated than ferrous sulphate, taken with vitamin C on an empty stomach. Low haemoglobin with high MCV points to B12 or folate deficiency — methylcobalamin (1,000mcg daily) and/or methylfolate (400–800mcg daily). Low WBC in the context of heavy training may respond to zinc (15–30mg daily), vitamin D optimisation, and reducing training volume. Persistently abnormal FBC results warrant investigation by your GP — do not self-treat without understanding the cause. Retest after 8–12 weeks of targeted supplementation to confirm improvement.
Research
Key study
Blood Biomarker Profiling and Monitoring for High-Performance Physiology and Nutrition: Current Perspectives, Limitations and Recommendations
Pedlar CR, Newell J, Lewis NA
Sports Medicine (2019)
DOI: 10.1007/s40279-019-01158-xRelated Biomarkers
Inflammation
Ferritin (Iron Stores)
Optimal: 80-150 ng/mL
Vitamins & Minerals
Iron (Serum Iron, TIBC & Transferrin Saturation)
Optimal: 15-25 µmol/L (serum iron), 20-45% transferrin sat.
Vitamins & Minerals
Vitamin B12 (Cobalamin)
Optimal: 500-800 pg/mL
Vitamins & Minerals
Folate (Vitamin B9)
Optimal: 20-45 nmol/L
Related Guides
Test your FBC levels
FBC 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.