'It can negatively affect training adaptation and performance long before anaemia develops' – Is iron deficiency holding you back on the bike?

How does blood health influence performance, energy levels and recovery?

Overall blood health, especially iron status, plays a major role in endurance performance, energy levels and recovery, even in athletes who are training well and eating adequately. Endurance performance is not determined by training alone and depends on many factors, including blood health, which is frequently overlooked. Healthy blood ensures oxygen and nutrients are delivered efficiently to working muscles.

How common are blood issues in cyclists?

Research in sports medicine and international athlete guidelines shows that low iron is common [30-50%] in endurance athletes, even without full anaemia. It can reduce aerobic capacity, make exercise feel harder at lower intensities, and limit training adaptation, with persistent tiredness despite “doing everything right”. Athletes can experience fatigue, reduced performance and slower recovery despite being disciplined with their training programme.

Which common blood imbalances can limit performance in cyclists?

Iron depletion is the most common blood imbalance in endurance athletes, but there are others. Research from Loughborough University and the University of Western Australia highlights that low haemoglobin, vitamin B12 or folate deficiency can affect red blood cell production and recovery.

Electrolyte imbalance and low vitamin D are also associated with muscle fatigue, weakness and increased risk of injury. Athletes may notice declining power or pace, elevated heart rate at familiar intensities, slower recovery between sessions or increased susceptibility to illness. These symptoms are often misattributed to overtraining rather than an underlying blood health issue

How can iron depletion affect cycling performance – including VO2max, power output, recovery and perceived effort?

When iron stores fall, oxygen delivery and use are compromised. VO2max can decline, leading to a drop in performance and slower recovery. Athletes often report that familiar training intensities feel disproportionately hard, with higher perceived effort and rising heart rate. Research published in Medicine & Science in Sports & Exercise, supported by laboratory studies from the University of Lausanne [in Switzerland] demonstrates that iron deficiency without anaemia significantly impairs endurance performance and training efficiency.

Why are female cyclists at greater risk of iron depletion?

Female athletes are particularly susceptible to iron depletion due to menstrual blood loss, higher iron demands from endurance training and, in some cases, lower dietary intake. Hormonal factors can also influence iron absorption and regulation. Large cohort studies cited in the British Journal of Sports Medicine, including work from Stanford University School of Medicine, consistently show higher rates of iron deficiency in female endurance athletes.

What signs should cyclists recognise as possible indicators of iron depletion?

Iron depletion can be difficult to spot early, as haemoglobin may remain normal while iron stores gradually decline. Cyclists may first notice subtle but persistent changes in performance and wellbeing. Some common signs include unexplained fatigue, reduced endurance, slower recovery, and rising perceived effort. Athletes may also experience declining power output, an unusually elevated heart rate at familiar intensities, breathlessness on minimal exertion, or increased susceptibility to illness.

These symptoms are often mistaken for overtraining or poor conditioning, but can reflect an underlying blood health issue. For this reason, early detection is important, as iron depletion can negatively affect training adaptation and performance long before anaemia develops.

Suspect Low Iron? Next steps for cyclists

• Get tested Arrange a blood test if you notice unusual fatigue, poorer recovery, falling performance or training feeling harder than normal.
• Start with nutrition Increase iron-rich foods, add vitamin C to aid absorption, and avoid tea/coffee close to meals.
• Use supplements carefully Oral iron may help but can cause stomach upset and be less effective during heavy training blocks.
• Seek medical follow-up Persistent symptoms or low results need further investigation.
• Consider clinical treatment In confirmed deficiency where tablets fail or aren’t tolerated, medically supervised iron infusion may be appropriate to restore levels and support consistent training and recovery.

Meet the Expert

Dr Susan Jain is the lead doctor at Revive and Reset (reviveandreset.com), a Harley Street clinic specialising in iron deficiency and anaemia. She is also a consultant in anaesthetics and intensive care medicine, with more than 25 years of clinical experience.