Iron deficiency is the most common nutritional deficiency on the planet, affecting an estimated two billion people. Its leading symptom is fatigue, which is also the symptom of overwork, poor sleep, stress, depression, thyroid problems and simply being a person with a busy life.
So it gets missed. People spend years assuming they are just tired, when a blood test costing very little would have found a treatable cause.
What iron actually does
Iron sits at the centre of haemoglobin, the protein in red blood cells that carries oxygen from your lungs to every tissue in your body. Without enough iron, you make fewer and smaller red blood cells, and each carries less oxygen.
The result is not a specific disease of one organ. It is a general shortage of oxygen delivery, which is why the symptoms are so diffuse and so easy to dismiss.
Iron is also required by enzymes involved in energy production, immune function and brain development — which is why symptoms can appear before anaemia is technically present.
Deficiency and anaemia are not the same thing
This distinction matters clinically and is frequently misunderstood.
Iron deficiency means your body's iron stores are depleted. Ferritin, the storage protein, is low.
Iron deficiency anaemia means the stores are so depleted that haemoglobin has fallen below normal too.
Stores empty first. You can feel unwell — tired, foggy, breathless on stairs — with low ferritin and a completely normal haemoglobin. Many people are told their blood count is fine and sent away, when the storage marker was never checked.
If you are being tested, the useful panel is a full blood count plus ferritin, and ideally transferrin saturation. Ferritin alone can be misleading, because it rises during inflammation and infection, which can mask a deficiency.
Symptoms
Common:
- Persistent fatigue that sleep does not fix
- Shortness of breath on mild exertion
- Pale skin, especially inside the lower eyelid and the nail beds
- Headaches and lightheadedness
- Cold hands and feet
- Poor concentration and low mood
- Hair thinning
- Reduced exercise tolerance — a run that used to feel easy now does not
More specific and worth knowing:
- Brittle, spoon-shaped nails
- Cracks at the corners of the mouth
- A sore, smooth tongue
- Restless legs syndrome — an underappreciated association
- Pica: craving non-food substances, most characteristically ice. Compulsive ice chewing is unusual enough to be a genuine clue.
Who is at risk
Menstruating women. By a wide margin the largest group. Heavy periods are the most common cause of iron deficiency in this population, and "heavy" is frequently normalised — many people have no reference point for what typical blood loss looks like.
Pregnancy. Iron requirements roughly double.
Infants, children and adolescents. Rapid growth increases demand.
Vegetarians and vegans. Plant iron is absorbed far less efficiently, though a well-planned diet manages this fine.
Frequent blood donors.
Endurance athletes. Through several mechanisms including foot-strike haemolysis and inflammation-driven absorption changes.
People with coeliac disease, inflammatory bowel disease, or who have had gastric surgery. Absorption is impaired.
Long-term use of acid-reducing medication. Stomach acid aids iron absorption.
Anyone over 50 with new iron deficiency and no obvious cause. This group needs proper investigation, because slow gastrointestinal bleeding — including from a tumour — is a leading cause and finding it early matters a great deal.
The two kinds of dietary iron
Haem iron comes from animal sources: red meat, liver, poultry, fish, shellfish. Absorption is high, roughly 15 to 35 percent, and is not much affected by what else is on the plate.
Non-haem iron comes from plants: lentils, beans, tofu, spinach, fortified cereals, pumpkin seeds, dried apricots. Absorption is much lower, in the region of 2 to 20 percent, and is heavily influenced by other foods eaten at the same time.
That second point is where most of the practical leverage lies.
Boosts non-haem absorption:
- Vitamin C, substantially. Citrus, peppers, tomatoes, strawberries alongside the meal.
- A small amount of meat or fish eaten with plant iron.
- Cooking acidic foods in cast iron.
Blocks non-haem absorption:
- Tea and coffee, significantly — the polyphenols bind iron. Separate them from meals by an hour or so.
- Calcium in large doses, including dairy and supplements.
- Phytates in whole grains and legumes, reduced by soaking, sprouting and fermenting.
A useful example: lentils with tomato and a squeeze of lemon, with the tea drunk an hour later rather than alongside, delivers far more usable iron than the identical lentils eaten with tea.
Supplements: the part people get wrong
If a doctor confirms deficiency, supplementation is usually needed — diet alone rarely refills depleted stores quickly.
The most useful recent finding concerns timing. Taking iron every day, or splitting a dose across the day, raises hepcidin, a hormone that then blocks absorption of subsequent doses. Several trials have found that alternate-day dosing, in a single dose, produces better total absorption than daily dosing — and causes fewer side effects.
Other practical points:
- Take on an empty stomach with vitamin C if tolerated; with a little food if not.
- Avoid taking it with tea, coffee, milk or calcium supplements.
- Constipation, nausea and dark stools are common. Dark stools are harmless and expected.
- Repletion takes months. Haemoglobin may normalise in six to eight weeks, but ferritin stores take considerably longer, and stopping when the blood count looks fine is the classic mistake that leads to relapse.
- Do not self-supplement long-term without testing. Iron overload is genuinely harmful, and some people carry haemochromatosis, a genetic condition causing excessive absorption.
The most important point
Iron deficiency is a symptom, not a diagnosis. The question is always why it happened.
In a menstruating person with heavy periods, the answer is usually obvious. In a man, or a postmenopausal woman, unexplained iron deficiency requires investigation of the gastrointestinal tract, because the body has no route to lose significant iron other than bleeding.
Treating the deficiency without asking the question fixes the number and misses the cause.
In short
If you have been tired for months and have put it down to life, ask for a full blood count and a ferritin level. It is an inexpensive test for one of the most common and most treatable causes of feeling permanently worn out — and the answer is either reassuring or genuinely useful.
Be the first to share a thought.