Why the need is higher
Periods regularly mean losing blood and therefore iron. That's why the recommended intake for menstruating women is clearly higher than for men of the same age. Add intensive endurance training and the risk rises further – the US health authority's fact sheet explicitly lists female athletes and women with heavy periods as risk groups.
The International Society of Sports Nutrition's position stand on female athletes' nutrition makes the same point: iron is one of the nutrients where a deficiency measurably impairs performance.
Does iron deficiency make your period stop?
We haven't found any evidence for that. The UK's National Health Service (NHS) lists these as common causes of a missed or late period: pregnancy, stress, the start of menopause, polycystic ovary syndrome (now called PMOS), sudden weight loss, being overweight, too much exercise, some hormonal contraceptives and breastfeeding. Iron deficiency isn't on that list.
The known link runs the other way. Heavy periods are one of the main causes of iron deficiency in women of reproductive age, and according to a 2023 review both are often dismissed as normal. If you bleed a lot, you lose iron. But your period doesn't stop because of it. How to recognise bleeding that's too heavy is in Heavy periods: how much is too much?.
In athletes, a missed period often has a different cause: too little energy compared with training. The International Olympic Committee updated this picture in 2023 under the name REDs. The International Society of Sports Nutrition's position stand also treats the two separately: iron as a nutrient question, energy deficiency as a separate and more serious topic. If you reach for iron when your period stops, you're probably treating the wrong thing.
Why still not on suspicion
Tiredness is an unspecific sign. It can come from too little sleep, too little energy overall, the thyroid – or indeed iron deficiency. If you guess, you may treat the wrong thing and miss the actual cause.
On top of that, too much iron isn't harmless. Common side effects are digestive problems, and the body has no effective way to get rid of an excess.
Which value counts
A blood count usually shows haemoglobin, and that seems reassuring as long as it's within range. But it falls late. The body empties its stores first, and only once they are empty does haemoglobin drop. A normal Hb value therefore doesn't rule out iron deficiency.
What shows the stores is ferritin. It clearly belongs in the picture when tiredness and a drop in performance are the issue. Ask for it specifically at your practice rather than relying on the standard blood count.
A systematic review that looked exclusively at female athletes drew the line at a ferritin below 40 µg/l. Below that, endurance performance was about 3 to 4 percent worse. That sounds small and isn't: it's the difference between a run that feels right and one where nothing works.
One catch: ferritin rises with inflammation and can then mask a deficiency. That's why it's often assessed together with an inflammation marker. It's one of the reasons why interpreting it belongs in the doctor's practice and not at the chemist.
What you can do regardless
- Eat iron-rich foods. Red meat, pulses, oats, pumpkin seeds, dark green vegetables.
- Add vitamin C. It noticeably improves absorption from plant sources – peppers, citrus fruit or a squeeze of lemon with your meal.
- Separate coffee and tea in time. They inhibit absorption; an hour's gap from the iron-rich meal is usually enough.
- Look more closely on a vegetarian or vegan diet. Iron from plants is absorbed less well than from animal sources.
What Rhythmus does about it
In the menstrual phase, the app highlights iron-rich meals, and in the supplements section it notes that iron is a question for the ferritin value, not for self-medication. You won't find a recommendation there to simply take iron – that would be exactly the mistake this text describes.