Iron and tiredness: what to keep an eye on in everyday life

Being tired is the complaint that one in two people brings to the doctor at some point. Tiredness has a thousand causes, most of which have nothing to do with iron — sleep deprivation, stress, screen hours, plain overload. Magnesium and B vitamins play a role in fatigue too — iron is therefore one of several possible levers, not the universal answer. But in a small share of cases, iron metabolism really is at the centre. Here's what you can keep an eye on yourself — and at which point your GP is the right person to talk to.

What iron does in the body

Iron is part of the red blood pigment haemoglobin. Haemoglobin binds oxygen in red blood cells and transports it from the lungs to every single cell of your body. Iron is also in muscle myoglobin, in enzymes of the respiratory chain and is involved in cell division — in short: iron is everywhere energy and oxygen come together.

In the EU list of authorised health claims (Regulation 432/2012), iron is listed, among other things, for the reduction of tiredness and fatigue, normal oxygen transport in the body, normal cognitive function, normal energy-yielding metabolism and the normal function of the immune system. That's the official reading — and it already says quite a bit about why undersupply can feel rather diffuse.

How much iron you need per day

Requirements differ markedly between men and women before menopause — the main reason is loss through menstruation:

Group	DGE recommendation (2023 update)
Men (19+)	11 mg / day
Women (19–50, premenopausal)	16 mg / day
Women 51+	14 mg / day
Pregnant	27 mg / day
Breastfeeding	16 mg / day
Adolescents 13–19 (m / f)	11 mg / 16 mg

The clearly higher recommendation in pregnancy is linked to building the placenta and supplying the child — not to the mother being "weaker". After menopause the requirement also stays slightly elevated (14 mg instead of 11 mg) because the body keeps using iron in stores and enzymes.

Where iron is in food — and why the source matters

Food (100 g)	Iron	Form
Pork liver	~ 18 mg	Heme
Pumpkin seeds	~ 12.5 mg	Non-heme
Tofu	~ 5.4 mg	Non-heme
Oats	~ 4.6 mg	Non-heme
Spinach (cooked)	~ 3.4 mg	Non-heme
Lentils (cooked)	~ 3.3 mg	Non-heme
Beef (lean)	~ 2.2 mg	Heme
Quinoa (cooked)	~ 1.5 mg	Non-heme

Does your food already cover it? — Iron

FoodPork liverPumpkin seedsTofuRolled oatsSpinach (cooked)Lentils (cooked)Beef (lean)Quinoa (cooked)

Portions

1

1 serving (125 g)

Your DGE reference valueBoys (13–18 y) (11 mg)Girls (13–18 y) (16 mg)Men (19–50 y) (11 mg)Women (19–50 y, premenopausal) (16 mg)Men (51+ y) (11 mg)Women (51+ y) (14 mg)Pregnant women (27 mg)Breastfeeding women (16 mg)

1 × 1 serving (125 g) Pork liver provide about 22.5 mg — 205% of your chosen DGE reference value (11 mg/day).

With 1 portions of Pork liver, you are there.

Orientation value — it does not replace a medical examination or advice. Source: DGE reference values for iron (2023)

Attentive readers will have noticed: lentils deliver more iron per 100 g than beef. Yet many guides talk as if meat were the iron source. The reason lies in the absorption rate:

• Heme iron from meat and fish is absorbed at 15–35 % efficiency.
• Non-heme iron from plant sources only reaches 2–20 %.

That means: from 100 g of lentils with 3.3 mg of iron, perhaps 0.1–0.7 mg actually arrives in your body. From 100 g of beef with 2.2 mg, it's already 0.3–0.8 mg. On paper, plant sources deliver more, in practice often the same or less. That's not an argument against plant-based eating — it's an argument for actively supporting absorption.

How to get more out of plant-based iron

There are simple levers, well-supported in many studies:

Promoter (with the meal)	Inhibitor (keep distance)
Vitamin C from peppers, lemon, sauerkraut	Coffee, black and green tea
Organic acids from fermented foods	Calcium-rich foods in the same bite
A little meat or fish in the same meal	Phytates from unprocessed legumes and whole grains

Practical: a glass of orange juice with lentil soup noticeably improves iron uptake. The espresso afterwards is best 30–60 minutes later.

When to look more closely

If you fall into one of the following groups, paying particular attention to iron intake is worthwhile:

• You have heavy menstruation.
• You're planning a pregnancy or are pregnant.
• You train regularly in endurance disciplines (marathon prep and similar).
• You eat strictly plant-based or vegetarian.
• You donate blood regularly — every donation costs about 200–250 mg of iron.

Attention doesn't mean: high-dose supplementation. Attention means: plan iron-rich foods deliberately, support uptake via vitamin C, and have recurring symptoms checked medically.

Germany's Federal Institute for Risk Assessment (BfR) recommends a maximum of 6 mg of iron per day from supplements. Higher amounts without a medically confirmed deficiency aren't useful and may push storage values into problematic territory over time.

Why self-diagnosis is a bad idea here

Tiredness is an extremely non-specific symptom. Iron deficiency is a medical diagnosis that belongs in a blood test — not in a knowledge hub. The standard values your GP will check:

• Haemoglobin (Hb) — the oxygen carrier itself
• Ferritin — the tissue iron storage
• if needed, transferrin saturation

Only this picture shows whether a dietary adjustment is enough or a deliberate supplement is needed. Highly dosed iron products on a hunch are not a good idea: they can lead to nausea, constipation and, long term, raised iron storage which can become problematic in turn.

Iron, B12 and folate work together

In red blood cell formation, iron, vitamin B12 and folate depend on each other. Anyone looking at a single substance "because of fatigue" not infrequently misses the actual bottleneck. More on this in the article B vitamins at a glance.

If you're often tired and unsure where it's coming from, the free Vital-Check is a good starting point — three minutes for a first assessment. With clear or persistent symptoms, though, clarification definitely belongs in medical hands.