Feeling “tired all the time” seems to have become an inescapable part of modern life, like ubiquitous social media, subscriptions to online platforms full of ads, or simply overwork. However, medical experts warn that this persistent fatigue may not be a simple consequence of our lifestyle, but rather a sign of a serious—and unfortunately very underdiagnosed—medical condition.
Iron deficiency is one of the most persistent nutritional deficiencies and the real reason behind the chronic exhaustion of millions of people. According to surgeon Toby Richards, director of the Iron Clinic in London, this chronic fatigue is often dismissed as psychological or normal, as it tends to affect young women (who are often ignored in the medical field). However, this persistent fatigue has a completely biological and treatable explanation.
Why is Iron Vital?
Iron is not just a mineral; it is the centerpiece of our body’s energy engine. Its absence paralyzes two fundamental biological processes that keep us active. Seventy percent of the iron in our bodies is found in hemoglobin, the protein inside red blood cells. The sole mission of red blood cells is to transport oxygen from the lungs to every corner of the body. When iron reserves are low, the oxygen supply is drastically reduced (known as hypoxia), causing us to feel general weakness and profound fatigue.
However, iron’s role does not end there; it is also essential for enzymes called cytochromes, which work inside the mitochondria. Cytochromes are indispensable for the electron transport chain process, the mechanism by which the body produces cellular energy (ATP). A lack of iron in this process means that, even with sufficient oxygen, the cell cannot convert it into energy efficiently, leading to an energy crisis that feels like exhaustion.
This is why many patients with iron deficiency describe their feeling as a “brain fog” that prevents them from thinking clearly.
The Diagnosis Trap
The main reason why iron deficiency is not diagnosed properly is the approach to blood testing.
Traditionally, only hemoglobin levels in the blood were studied, which identified iron deficiency anemia (IDA). However, the body is able to deplete its iron stores before sacrificing the iron circulating in the blood. These iron stores are stored by a protein called ferritin. Since people can have normal hemoglobin levels but low ferritin levels, they may already be experiencing extreme fatigue due to Non-Anemic Iron Deficiency (NAID).
While the cutoff for anemia may be 30 µg/L, in cases of chronic fatigue, experts recommend levels below 100 µg/L as an indicator of insufficient reserves requiring intervention. If you have persistent fatigue but your hemoglobin tests come back normal, request a specific ferritin test and a red blood cell count.
An Unavoidable Nutritional Gap that Leads to Being Tired
The reason why anemia affects young women more than any other group in society is due to a fundamental biological difference: menstruation. Women of reproductive age need almost twice as much iron per day as men. This is simply because they tend to bleed once a month.
This loss of menstrual blood leads to a chronic and periodic loss of iron that must be constantly replenished. The NHS nutritional guidelines make this clear distinction: the recommended daily allowance (RDA) for premenopausal women is 18 mg/day, while for adult men and postmenopausal women it is only 8 mg/day.
On the other hand, men need to take more zinc than women, as it plays an important role in male reproductive health for good prostate function and adequate testosterone synthesis. While adult women need only 8 mg/day of zinc, adult men need 11 mg/day.
Nutritional Thieves: Calcium and Caffeine
Even if we take iron supplements every day, modern diets presents many obstacles to proper absorption. Calcium, which is essential for health, inhibits absorption. Calcium competes directly with iron for the same transporters in the cells of the small intestine.
By saturating the receptors, it blocks the entry of iron into the bloodstream. This significantly reduces the amounts that the body can use. If you have anemia, we strongly recommend that you do not consume foods rich in calcium when taking iron. For example, if you are going to eat a beef steak, do not accompany it with a cream-based sauce or butter. If you are going to take an iron supplement, do not take it while having a cup of coffee (caffeine is also a powerful iron inhibitor).
On the other hand, there are iron absorption enhancers such as vitamin C. This is why many nutritionists recommend drinking orange juice with iron supplements and adding a little lemon to foods rich in heme iron.