Fatigue in women often has one underrated driver: iron loss through menstruation. Alongside that, thyroid, vitamin B12 and hormonal transitions play a part. Blood testing can make a few of those causes visible, but it is one puzzle piece, not a diagnosis.
My belief after hundreds of results: in women, iron gets checked too late. The tiredness is blamed on a busy life for months, while a low ferritin sometimes already tells part of the story.
According to RIVM figures, a sizeable share of Dutch adults report feeling tired regularly, and women report this more often than men. Being tired is normal. Fatigue that lasts for weeks deserves attention.
Why are women tired more often than men?
Women lose blood every month through menstruation, and with it iron. Hormones also swing more strongly across the cycle and the life stages. That combination means the same complaint in women often has a different cause than in men.
It is rarely one thing. Someone with heavy periods who sleeps poorly and has low iron feels the sum of three things at once.
In men, the picture shifts toward testosterone and thyroid. Read about that in fatigue in men. For the full overview there is our pillar on causes of fatigue.
How can menstruation affect your energy?
Every period costs iron. With heavy or long bleeding, the iron store can slowly drop, long before anaemia appears. A low ferritin sometimes goes together with fatigue and concentration problems, though often more factors play a part.
The sneaky part is that this happens gradually. You feel a little flatter each month, and you put it down to work or your nights.
Ferritin says something about your iron store, haemoglobin about your red blood cells. If you want to know how to spot a deficiency, read spotting iron deficiency with a blood test. An abnormal value is not a diagnosis, but a starting point for a talk with your GP.
Which causes come into view most often in women?
The causes run from iron and thyroid to vitamins and hormones. Often they work together. The table below puts common causes next to the blood value that sometimes relates, and what an abnormality can mean. See it as a checklist, not a verdict.
| Possible cause | Related blood value | What an abnormality can mean |
|---|---|---|
| Iron loss through menstruation | Ferritin, haemoglobin | Low iron can go together with fatigue and breathlessness |
| Slow thyroid | TSH | More common in women and can cause fatigue and feeling cold |
| Vitamin B12 deficiency | Vitamin B12 | A deficiency can cause fatigue and tingling, especially on a plant-based diet |
| Pregnancy or recovery after | Ferritin | Iron need rises; a deficiency is more common in this period |
| Menopause and hormonal shift | Hormone values | Sleep and mood vary; fatigue sometimes fits this picture |
If you want a number of these values measured at once, a fatigue blood test fits. If you mainly suspect your hormones, a hormone test for women may fit better.
Does fatigue change by life stage?
Yes, the likely causes shift along with it. Roughly three stages call for their own view: the menstruating years, a pregnancy, and the period around menopause. In each stage, what is most likely changes.
In the menstruating years, iron comes first. Heavy or long bleeding can deplete the store, and ferritin gives insight into that.
During and after a pregnancy, iron need rises sharply. Many women feel exhausted in that period, and low iron is a common explanation. Around menopause the picture changes again: hormones swing, sleep often gets more restless, and fatigue sometimes fits that whole. Read about that in oestrogen and menopause.
Picture a woman of 49 who has slept worse for a year and has an afternoon dip more often. Her iron is fine, but her nights have been restless for months. No single value then explains everything.
Which blood values give insight in women?
A number of values come into view most often in women. They do not prove a cause, but can help understand why you feel tired. A doctor always assesses the whole picture, not one single number.
- Ferritin and haemoglobin: give insight into your iron store and red blood cells, especially relevant with heavy periods.
- TSH: a slow thyroid is more common in women and can worsen fatigue.
- Vitamin B12: a deficiency can cause fatigue, with a higher risk on a plant-based diet or after pregnancy.
Which test fits your situation depends on your complaints and your life stage. Your GP can help you decide what makes sense.
What if your blood values are normal but you are still tired?
I hear this often: everything within range, and yet you are exhausted. A normal result is no proof that nothing is going on. It means the cause probably does not lie in those tested values.
Common explanations are sleep quality, long-term stress, too little movement or a low mood. You do not always see those in blood.
If you stay tired despite normal values, discuss that with your GP. Sometimes the fatigue is partly unexplained, and that does not make your complaints less real.
Frequently asked questions about fatigue in women
Is fatigue in women more often due to iron deficiency?
Iron loss through menstruation is a common explanation, certainly with heavy bleeding. A low ferritin can go together with fatigue, though often more factors play a part. Your GP can discuss this with you.
Which blood values relate to tiredness in women?
Ferritin, haemoglobin, TSH and vitamin B12 often come into view. They do not prove a cause, but can explain why you feel tired. A doctor assesses the whole picture.
Can menopause cause fatigue?
Around menopause hormones swing and sleep often gets more restless. Fatigue sometimes fits that picture. Blood rules out other causes, but does not pin down menopause one-to-one.
What I would suggest
Do not wait too long to look at your iron, certainly with heavy periods, but do not panic over one abnormal value either. Fatigue in women is an interplay of iron, hormones and lifestyle, and blood is a tool within it. Discuss your complaints and your result with your GP, especially if the tiredness persists. Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
References
- RIVM. Fatigue and health: figures and context. Accessed 2026.
- Thuisarts.nl / NHG. I am tired. Dutch College of General Practitioners. Accessed 2026.
- Netherlands Nutrition Centre. Iron in the diet. Accessed 2026.
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