Iron Deficiency as a Cause of Fatigue
Iron deficiency — even without progressing to full anaemia — is one of the most common causes of persistent fatigue, particularly in women of reproductive age, vegetarians, and frequent blood donors. It's also one of the most reliably fixable.
How iron deficiency causes fatigue
Iron is essential for haemoglobin — the protein in red blood cells that carries oxygen to your tissues and muscles. Low iron means lower oxygen delivery, which directly reduces energy production at the cellular level. Even mildly low ferritin (stored iron) causes fatigue before haemoglobin levels drop.
This is why standard 'anaemia' tests can miss iron deficiency fatigue — a normal haemoglobin level doesn't rule out iron depletion. Ferritin (stored iron) should be tested specifically, and optimal levels for energy are generally above 50–70 μg/L, even though labs mark anything above 12–20 as 'normal'.
Who is most at risk
Women with heavy periods are the highest-risk group — losing significantly more iron monthly than men or women with lighter cycles. Pregnancy increases iron demand substantially. Vegetarians and vegans consume non-haem iron (from plants), which absorbs less efficiently than haem iron from meat.
Athletes — particularly long-distance runners — experience accelerated red blood cell breakdown (foot-strike haemolysis) and increased iron losses through sweat, making iron deficiency common even with adequate dietary intake.
Testing and treatment
Ask your GP for a full iron panel including ferritin. If ferritin is below 50, supplementation is often warranted even if haemoglobin is normal. Iron bisglycinate is better tolerated than ferrous sulphate (less constipation and nausea) and absorbs well.
Vitamin C taken alongside iron supplements increases absorption. Avoid taking iron with coffee, tea, calcium, or other minerals, which all inhibit absorption. Improvements in energy typically appear within 4–8 weeks of supplementation.
Our assessment screens for the lifestyle patterns associated with iron deficiency and flags it as a likely contributor to your fatigue.
Frequently Asked Questions
What are the symptoms of iron deficiency fatigue?
Common symptoms include persistent tiredness, weakness, and difficulty concentrating, often accompanied by pale skin and shortness of breath.
How can I test for iron deficiency?
You can ask your GP for a full iron panel that includes ferritin levels to accurately assess your iron status.
What is the best way to treat iron deficiency?
Iron supplementation, particularly with iron bisglycinate, along with vitamin C to enhance absorption, is often recommended for treating iron deficiency.
Who is most likely to experience iron deficiency?
Women with heavy menstrual periods, pregnant women, vegetarians, and athletes are among those most at risk for iron deficiency.