The short answer: Iron stores refill slowly. Your haemoglobin can recover while your ferritin is still low. A ferritin that "went up" may also still be under the new 30 or 50 cut-offs. And tiredness has many other causes, from sleep to thyroid, that iron cannot fix.
Why are so many women asking this right now?
In September 2026, the American Society of Hematology (ASH) published new guidelines for diagnosing iron deficiency [1]. News-Medical summarised them on 9 October 2026, and coverage is still spreading [2].
The big change is the ferritin cut-off. Ferritin is the protein that stores iron in your body. For most adults, ASH now suggests that a ferritin of 30 ng/mL or lower means iron deficiency [2]. The old line was 15 [2].
For women with heavy periods, symptoms or other risk factors, the line may go up to 50 [2]. We explain those numbers in our post on new ferritin cut-offs.
So many women are rechecking old reports. And some are finding a frustrating pattern. They took iron, the number moved, and they still feel like a phone on 5% battery.
Why am I still tired if my ferritin went up?
The most common reason is simple, because a number going up is not the same as enough.
Say your ferritin was 12 and it is now 25. That is real progress, but under the new ASH thresholds, 25 is still iron deficiency for most adults [2]. If you have heavy periods, the guideline says a threshold of 50 may fit you better [2].
Many lab reports still print a low "normal" limit, like 15. So a report can say "normal" while the new guideline would say "still low". Always ask for the actual number on the report, not just the word next to it.
The second reason is time, because iron stores take months to refill, not weeks. The NHS says people with iron deficiency anaemia usually need iron tablets for about 6 months [4]. Your doctor may repeat blood tests over the following months to check progress [4].
Is haemoglobin the same as iron stores?
No, and this confuses a lot of people at the chemist and in the clinic. Haemoglobin is the protein in red blood cells that carries oxygen. Ferritin shows how much iron is saved in reserve.
Think of haemoglobin as the cash in your wallet, and ferritin as your savings account. Your body spends incoming iron on red blood cells first. Only what is left over at the end of the month goes into savings.
A 2026 case report in the journal Cureus shows how far apart the two can be [6]. A 32-year-old woman with heavy periods took iron tablets regularly. Her haemoglobin rose from 9.1 to 9.9 g/dL [6]. But her ferritin stayed at 1 ng/mL, which means her reserves were almost empty [6].
That is one extreme case, not a typical result for most women. Her ferritin only climbed to 52 after she was given iron through a drip [6]. Still, it shows why a better haemoglobin does not mean your stores are full.
How much does iron actually help with tiredness?
There is good evidence that it can help, for the right person. A 2012 trial in the Canadian Medical Association Journal tested this directly [3].
It included 198 women aged 18 to 53 who felt tired and had a ferritin below 50 [3]. None of them had anaemia [3]. Half got 80 mg of iron a day for 12 weeks, and the other half got a dummy pill, called a placebo [3].
Fatigue scores fell by 47.7% in the iron group [3]. But they also fell by 28.8% in the placebo group [3]. So iron helped, but part of the improvement happened even without it.
There is another detail worth knowing from this trial. After 12 weeks, ferritin was only about 11 ng/mL higher with iron than with placebo [3]. Iron also made no clear difference to quality of life, mood or anxiety [3].
The honest takeaway is this. Iron can lift tiredness that comes from low iron. It does not touch tiredness that comes from somewhere else.
What else could be making you tired?
The NHS lists many common causes of tiredness [5]. Most of them have nothing to do with iron, which is why a tablet alone may not fix them.
- Sleep. Too little sleep or insomnia, meaning trouble falling or staying asleep [5].
- Stress and mood. Stress, depression, grief, or looking after a new baby [5].
- Hormone changes. Pregnancy and menopause can both bring tiredness [5].
- Sleep apnoea. Loud snoring with gasping or choking at night [5].
- Diabetes. Feeling very thirsty and peeing more often, especially at night [5].
- Thyroid problems. An overactive thyroid can leave you tired but restless and anxious [5].
Low iron is not the only kind of anaemia either. A full blood count also checks for vitamin B12 or folate deficiency anaemia, the NHS says [4].
The NHS advice is clear. See a doctor if you have been tired for a few weeks without knowing why [5]. The same goes if tiredness is affecting your daily life [5].
Is there an "optimal" ferritin, like 75 or 100?
You will find this claim on Reddit and Instagram, where some people say everyone feels best at 75 to 100. We could not find any guideline that says so.
The ASH thresholds are diagnostic lines, used to decide if you are iron deficient [2]. They are not targets that everyone should try to reach. The guideline also says these thresholds should not be automatic triggers for taking iron [2].
The evidence behind the new thresholds is rated low certainty [2]. ASH says the benefits of finding more cases must be weighed against false diagnoses and unneeded iron [2].
So more iron is not always better, even when you still feel tired. Do not keep taking high-dose iron for months without a repeat test. And keep iron tablets away from children, because an overdose in a young child can be fatal [4].
What should you ask at your next blood test?
Go in with a short list, because it makes a busy ten-minute appointment much more useful.
- Ferritin and haemoglobin together. Ask for both numbers, not just "normal".
- Transferrin saturation, if you have inflammation. Inflammation can push ferritin up even when iron is low. With anaemia of inflammation, ASH suggests testing ferritin and transferrin saturation, a measure of how much iron is moving in your blood [2].
- B12 and folate. These can cause a different kind of anaemia [4].
- Thyroid and blood sugar. Blood tests can check for diabetes and an overactive thyroid [5].
- The cause. If your periods are heavy, say so. Fixing only the number while the blood loss continues is like filling a leaking bucket.
Vaucher's trial team suggested checking blood markers after about six weeks of iron [3]. That gives you a clear sign of whether it is working.
What this means if you...
...have heavy periods and your ferritin is between 30 and 50
Under the new guideline, you may still count as iron deficient [2]. Ask your doctor if the 50 threshold applies to you. Ask about the heavy bleeding too, since that is the leak.
...your report says "normal" but you still feel drained
Check the actual ferritin number against the new cut-offs. If it is above 50, iron may not be your main problem. Ask about sleep, mood, thyroid, blood sugar and B12.
...you started iron a few weeks ago
Give it time and take it exactly as your doctor prescribed. If side effects are making you skip doses, read why so many women stop iron tablets. Then talk to your doctor before you change the dose, timing or brand.
Where AIM stands
We are building FORGE, launching soon. It is a daily sachet with 9 mg of elemental iron as iron bisglycinate and 80 mg of vitamin C. It also has 5 g of creatine monohydrate and BioPerine. 9 mg is a daily top-up amount. It is not a replacement for iron your doctor prescribes for deficiency, and we will never say it is. If you are tired all the time, get tested first and let the numbers guide you.
Frequently asked questions
Why am I still tired after taking iron for two months?
Iron stores refill slowly, and the NHS says iron tablets are usually taken for about 6 months. Your ferritin may have risen but still sit under the new 30 or 50 cut-offs. Tiredness also has many other causes, like poor sleep, stress, thyroid problems or B12 deficiency, so ask your doctor to look wider.
Can my haemoglobin be normal while my ferritin is low?
Yes. Haemoglobin carries oxygen in your red blood cells, while ferritin shows your iron reserves. Your body refills haemoglobin first. A 2026 case report described a woman whose haemoglobin rose on iron tablets while her ferritin stayed at 1 ng/mL. So a better haemoglobin does not mean your stores are full.
What ferritin level is considered iron deficiency in 2026?
The American Society of Hematology's 2026 guideline suggests 30 ng/mL or lower for most adults, up from 15. A threshold of 50 may apply if you have heavy periods, symptoms or other risk factors. These are suggestions based on low-certainty evidence, so discuss your own number with your doctor.
Is a ferritin of 100 better than 50?
No guideline we found sets 75 or 100 as a target for everyone. The 2026 thresholds are for deciding whether you are deficient, not numbers to chase. The guideline warns against using thresholds as automatic triggers for iron. More iron is not always better, so do not keep taking high doses without a repeat test.
How long does it take for iron to reduce tiredness?
In a 2012 trial of 198 tired women with ferritin below 50, iron reduced fatigue more than a placebo over 12 weeks. The researchers suggested checking blood markers after about six weeks. The placebo group also improved, so if you feel no change after a few months, ask your doctor about other causes.
Sources
- Powers JM, Lim MY, Achebe MQ, et al. American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Advances, 2026. doi.org/10.1182/bloodadvances.2025015950
- Thomas L. New iron deficiency guidelines raise key blood test cutoffs. News-Medical, 9 October 2026. news-medical.net
- Vaucher P, Druais PL, Waldvogel S, Favrat B. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. CMAJ, 2012, 184(11):1247-1254. doi.org/10.1503/cmaj.110950 (PMID 22777991)
- NHS. Iron deficiency anaemia. nhs.uk
- NHS. Tiredness and fatigue. nhs.uk
- Lee A, Morales S, Quiroz E. Desiderosmia-associated iron deficiency: a case report and review of the literature. Cureus, 2026, 18(4). doi.org/10.7759/cureus.106380
This article is for education only and is not medical advice. Supplements are not a substitute for a varied diet or for treatment from a qualified doctor. If you are pregnant, breastfeeding, on medication, or have a medical condition, talk to your doctor before starting any supplement. Individual results vary.
Photo: Ron Lach via Pexels.