Tired all the time but your bloods are "normal"? The ferritin trial explained
Sometimes, low iron stores are part of the picture even when your haemoglobin is normal. In a double-blind trial of 144 tired women without anaemia, iron reduced fatigue about twice as much as a placebo, but only in women whose ferritin was 50 µg/L or less. It was a small, short trial, and too much iron is harmful, so the message is to know your ferritin, not to start iron on a hunch. Alongside that, regular meals with iron-rich foods, sensible caffeine timing and pacing your energy have good support.
"Your blood tests are normal." If you're exhausted every day, those words can feel like being told it's all in your head. But a "normal" result usually means your haemoglobin, the part of the blood that carries oxygen, is in range. It doesn't always tell you about your iron stores, which are measured by a different test called ferritin.
A Swiss trial asked a simple question: if a tired woman isn't anaemic, can low iron stores still be behind her fatigue? Here's what it found, how much weight it can carry, and what you can do about your energy day to day.
What the trial did
The trial, published in the BMJ in 2003, recruited women from GP practices in western Switzerland.
- Who: 144 women aged 18 to 55 whose main complaint was unexplained fatigue, and who were not anaemic.
- What: 80 mg of iron a day or an identical-looking placebo, for 4 weeks. Neither the women nor the doctors knew who had which (double-blind).
- What was measured: fatigue on a 0 to 10 scale, before and after.
What it found
| Group | Drop in fatigue | What it means | Strength |
|---|---|---|---|
| Iron | 29% (1.82 points) | About twice the improvement seen with placebo | Statistically significant |
| Placebo | 13% (0.85 points) | A real placebo effect, which is common with fatigue | Comparison |
| Difference | 0.95 points (0.32 to 1.62), p = 0.004 | Unlikely to be chance | Moderate |
| Ferritin above 50 µg/L | No clear benefit | Iron only helped women with low stores | Subgroup |
The key detail is in the last row. The benefit was only seen in women whose ferritin was 50 µg/L or less. Iron didn't help women whose stores were already healthy, which is exactly what you'd expect if low iron was the real cause.
How robust is this?
A double-blind, placebo-controlled trial is a strong design, and the result makes biological sense. But it's one trial, and it has real limitations:
- Small and short. 144 women for 4 weeks. We don't know how long the effect lasts.
- Blinding wasn't perfect. Iron can darken stools, so some women may have guessed they were on iron, and fatigue is a subjective score that expectations can influence.
- Funded by the iron manufacturer. Funding doesn't make a result wrong, but it's worth knowing.
- Only women, only one measure of iron. Ferritin can also rise with inflammation, so it isn't a perfect measure of iron stores.
What has good evidence for steadier energy
Fatigue almost never has a single cause or a single fix. These everyday foundations have good support, whatever your ferritin turns out to be.
| Change | What the research shows | Evidence |
|---|---|---|
| Regular meals with protein and fibre | Regular, balanced meals support steady energy. NICE advises people with ME/CFS to follow a balanced diet, and the NHS Eatwell Guide sets out the same pattern for everyone. | UK guidance |
| Iron-rich foods most days | The NHS lists dark-green leafy vegetables, iron-fortified breakfast cereals, meat, dried fruit such as apricots, and pulses such as beans, peas and lentils as good sources of iron. | UK guidance |
| Keeping caffeine to earlier in the day | In a small sleep study, 400 mg of caffeine (about 4 mugs of coffee) taken even 6 hours before bed cut sleep by more than an hour. Poor sleep feeds the next day's tiredness. | Good |
| Pacing your energy across the week | For ME/CFS, NICE recommends energy management: staying within your energy limit and planning rest, rather than pushing through on good days and crashing afterwards. | UK guidance |
These sound simple. The hard part is fitting them into a life that's already running on empty, which is where support makes the difference.
When you're exhausted, every change has to be easy
The last thing a tired person needs is a 20-step plan. My coaching starts from where your energy is now, and builds one small habit at a time.
Find your patterns
We track energy, sleep, food, stress and activity for a few weeks, so you can see what drains you and what helps, instead of guessing.
Low-effort, iron-rich meals
We build a handful of quick meals and snacks with iron-rich foods you actually like, for days when cooking feels impossible.
A sleep and caffeine routine
We adjust your caffeine timing and evening routine step by step, so better sleep doesn't depend on willpower.
Pacing that fits your week
We plan your week around your real energy, so good days don't turn into three-day crashes.
My take
Fatigue is one of the most common reasons people come to me, and one of the most frustrating, because it's invisible and it rarely has a single cause. Knowing your ferritin can rule one thing in or out. After that, the everyday basics make a real difference: how you eat, how you sleep, how you use caffeine, and how you spread your energy across the week.
Building those habits when you're running on empty is hard to do alone. That's exactly what I help my clients with, one small step at a time.
Frequently asked questions
Can you have low ferritin with normal haemoglobin?
Yes. Ferritin reflects your iron stores, and they can run low before your haemoglobin drops. That's called iron deficiency without anaemia.
What ferritin level was linked to fatigue in the trial?
In the Verdon trial, iron only reduced fatigue in women whose ferritin was 50 µg/L or less. Women with higher ferritin didn't benefit.
Should I take iron tablets if I'm tired?
Not without a blood test. Too much iron is harmful, and fatigue has many possible causes. Knowing your ferritin first tells you whether iron is even relevant to you.
Which foods are high in iron?
The NHS lists dark-green leafy vegetables, iron-fortified cereals, meat, dried fruit such as apricots, and beans, peas and lentils.
Does coffee make fatigue worse?
It can, indirectly. In one small study, caffeine taken 6 hours before bed cut sleep by more than an hour, and poor sleep makes the next day harder.
Sources
- Verdon F, Burnand B, Fallab Stubi CL, et al. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ 2003;326:1124. Read it
- Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med 2013;9:1195-1200.
- NICE NG206. Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management. 2021. Read it
- NHS. Iron deficiency anaemia. Read it
- Public Health England. The Eatwell Guide. 2016. Read it
Follow @habitiahealth on Instagram for a new evidence check most days.
I'm Shivy, a certified Integrative Nutrition Health Coach (Institute for Integrative Nutrition, 2020). I have a degree in biology and a master's in environmental science, and I've lived with psoriasis since 2019. I read the research on food, sleep, stress and movement and turn it into small, realistic habits. More about me.
This article is education, not medical advice. Always follow the advice of your GP or medical team, and check with them before changing your diet or supplements.
