"I have anaemia, my doctor told me to move more": we hear this phrase often, and usually the advice is good. The problem is what gets attached to it by the articles found online, namely the idea that by training your haemoglobin will go up. That part is not proven, and it is worth knowing before you start, because it completely changes what you should expect in the first few weeks and what you do if nothing happens.
In this article you will find what is documented about the relationship between anaemia and exercise, which signs to check before lacing up your shoes, how to adjust intensity when you run short of breath for efforts that used to be trivial, and why in endurance athletes the picture is reversed.
⚠ Important: read this before continuing
The exercises and advice in this article are general guidance and may not suit your situation. Every person has a unique clinical history: what works for others could be counterproductive for you.
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First of all: what not to train
Anaemia is not a diagnosis, it is a laboratory result. It says that haemoglobin is low, not why, and the why matters far more than the training programme. These situations need to be looked at before anything is trained:
- Chest pain or tightness, palpitations even when still, fainting or near-fainting during effort: these are cardiac symptoms, and with low haemoglobin the heart is already working in difficult conditions. You stop and get checked, you do not "try to go slowly".
- Shortness of breath at rest or while speaking, not just when climbing stairs.
- Black, tar-like stools, blood in the stool or vomiting blood: this is a suspected bleed in the digestive tract, and it is urgent.
- Iron-deficiency anaemia in a man or in a woman after menopause, with no obvious cause. This is the point almost nobody writes about: British gastroenterology guidelines estimate that about one third of men and postmenopausal women presenting with iron-deficiency anaemia have an underlying pathological cause, most often in the digestive tract, so much so that in the United Kingdom unexplained iron-deficiency anaemia, in anyone within the risk categories, is considered a reason for rapid referral to a specialist even in the absence of specific symptoms.
- Very heavy periods, with clots or the need to change protection every few hours: one of the most frequent causes in women of reproductive age, and treatable, but it should be mentioned to the doctor rather than endured.
- Unexplained weight loss, fever that does not go away, night sweats, swollen lymph nodes.
None of these conditions improves because you start walking, and some get worse if you wait. When we talk about anaemia and exercise we take for granted that you already know where the low value comes from: if you do not know yet, that is the first step, not the second.
What the studies really say
Here comes the uncomfortable part, and we are writing it anyway.
In iron-deficiency anaemia, by far the most common type, no systematic reviews have shown that training raises haemoglobin. What raises it, in the reviews, is iron. The Cochrane review of daily iron supplementation in menstruating women gathered 67 studies and 8,506 participants: those receiving iron were much less likely to be anaemic at the end of the intervention (relative risk 0.39, 10 studies, 3,273 women, moderate-quality evidence) and had haemoglobin higher by 5.30 g/L on average compared with control (51 studies, 6,861 women, high quality). The limitation should also be stated: only 10 of the 67 included studies were judged overall to be at low risk of bias. The same review also shows the costs: more gastrointestinal disturbances (low-quality evidence), more constipation and more loose stools or diarrhoea compared with control (high quality). Iron is a treatment, with effects and side effects, and that is why it is taken after a test and not by guesswork.
There is one exception, however, and it is right to write it down: in people on dialysis, where anaemia depends on kidney disease and not on simple iron deficiency, a meta-analysis of 23 studies with 1,214 participants found that aerobic and resistance exercise programmes built into the treatment pathway improved, besides physical capacity and quality of life, haemoglobin too, compared with usual care. It is a specific clinical context, followed by the nephrologist: there, the relationship between anaemia and exercise is read within a treatment pathway, and it does not apply to someone who arrives here with a low iron level to correct.
In the reviews on iron-deficiency anaemia, exercise is not the variable that shifts haemoglobin. It is less exciting news, but more useful, because it directs attention where it is needed: first you treat the cause, then movement serves to avoid losing what you have and to regain fitness.
There is, however, a second half to the story, and it is entirely in favour of movement. When iron is corrected, the capacity to exert yourself really does improve. A systematic review with meta-analysis conducted on women of reproductive age (24 studies identified, 22 with usable data, and only 3 judged overall to be at low risk of bias) found that daily iron supplementation, compared with control, improved maximal oxygen uptake by 2.35 ml per kg per minute (18 studies) and reduced by about 4 beats per minute the heart rate needed to sustain the same workload (6 studies). Put simply: the same climb, with the same body, costs less.
And there is a third finding, which dismantles the most widespread shortcut ("I am tired, I'll take iron"). In adults who are iron-deficient but not anaemic, a systematic review of 18 randomised trials with 1,170 patients found that supplementation reduced the tiredness people reported (standardised mean difference -0.38, 4 studies, 714 participants), but did not improve objective measures of physical capacity: for maximal oxygen uptake the difference was not significant (standardised mean difference 0.11, 95% confidence interval -0.15 to 0.37, 9 studies, 235 participants). You feel better, but the engine does not perform any better.
For fairness, the other side should also be said: the authors of that review do not conclude that iron is useless in these cases. They consider it reasonable to consider iron-rich foods or supplementation precisely for tiredness symptoms, even without a documented anaemia, and in the same analysis haemoglobin did still rise a little (4.01 g/L, 12 studies, 298 participants). The realistic goal changes: how you feel, not the stopwatch. It is a distinction worth keeping in mind when you assess your progress too.
How to use this information
- Moving with anaemia makes sense, but for the right reasons: maintaining muscle mass, tolerance to effort, mood and the habit of movement while the cause is being treated.
- Do not expect training to change your values. If after weeks your haemoglobin has not moved, it is not because you are not training enough.
- The first aim in the early weeks is not to improve, it is to avoid making the day worse: getting to the evening with energy left, not drained.
- The moment when your training will really start to pay off will be when the cause has been treated. Those who train while deficient reap less than they sow.
Why you run short of breath for efforts that used to be trivial
Haemoglobin is the protein that carries oxygen in the blood. If there is less of it, less oxygen reaches the muscles for every litre of blood pumped, and the body has only one way to compensate: circulate more blood, that is, raise the heart rate. That is why the typical sensation is not "aching legs" but palpitations and air hunger out of proportion to what you are doing: two flights of stairs with the heart racing, when a month earlier you did not think twice about it.
It is also worth knowing where the threshold lies. The most recent international analysis of reference values, based on healthy population samples, places the fifth percentile of haemoglobin at 119.7 g/L in non-pregnant women aged 18 to 65 (3,640 participants) and at 134.9 g/L in men (2,377 participants); for people over 65 the available data were not sufficient. Below those thresholds one speaks of anaemia, but the number alone does not tell you how limited you are: two people with the same value can be in very different states, depending on how quickly it fell and what lies underneath.
An important tip: before trying these exercises, make sure you have received a correct diagnosis. People often think they have one problem when the real cause of the pain is another. Doing the wrong exercises can make things worse instead of better.
How to adjust intensity (without a heart rate monitor)
The first tool that misleads, when it comes to anaemia and exercise, is the one everyone relies on: the heart rate monitor is deceptive, because the pulse is high to compensate and not because you are pushing. The more practical reference is a different one, and it costs nothing: the talk test. If you can speak in full sentences while moving, the intensity is suitable. If you can only answer with single words, you have already passed the point at which your body, today, is working well.
The other rules we give patients are three:
- Stop before you are exhausted, not when you are. With anaemia recovery is slower, and the session that drains you also takes away the next day.
- Change one thing at a time. First the duration, then the frequency, and only at the end the intensity. Increasing everything together is the fastest way to have to stop.
- Look at the day after, not at the session. If the tiredness clears by the following evening, the dose is sustainable. If it leaves you flat for two days, it is too much, even though at the time it seemed little.
Heat deserves a separate line: hot and humid environments increase cardiovascular work for the same effort, and dehydration worsens symptoms you already have. If you have little margin, move the activity to the cooler hours and drink water.
When to stop straight away
Dizziness, blurred vision, nausea, sudden pallor, chest pain, confusion. These are not signals to push through: you stop, you sit down, and if they do not clear quickly you call for help. These symptoms during light activity deserve a conversation with the doctor even if they then pass.
Which activities to choose
In the phases when the margin is small, whatever is continuous, low intensity and easy to interrupt works well: walking on flat ground, stationary cycling at low resistance, gentle swimming, yoga, tai chi, joint mobility. These are activities you can stop at any moment without being left "in the middle" of an exercise, and this is no small thing when you do not know how you will react.
Strength work is also possible, and worth doing: moderate loads, few repetitions per set and long rests, which is exactly the opposite of the high-density circuits in fashion. The goal in this phase is not to build muscle, it is to keep it.
Those who also suffer from night-time leg cramps often benefit from moving the mobility work to the evening. And if the tiredness you feel is not proportionate to the haemoglobin value and does not pass with rest, it is worth reading what we know about chronic fatigue syndrome, where the rules for movement are even more cautious.
Nutrition: what helps and what gets in the way
Diet does not replace treatment, but it can work against it or in its favour. The lesser-known point concerns absorption: the review on anaemia in athletes notes that some dietary components, such as phytates and polyphenols, reduce iron absorption, while ascorbic acid (vitamin C) increases it.
From this come the practical indications we give:
- Iron-rich foods (meat, pulses, dark green leafy vegetables) combined with a source of vitamin C in the same meal: a glass of fresh orange juice, lemon on pulses, raw tomato.
- Coffee and tea away from main meals, for the same reason: they are rich in polyphenols.
- If you are taking iron on medical advice, the best-documented side effects are gastrointestinal, especially constipation and loose stools: if they appear, do not abandon the treatment on your own, tell the doctor, who may change the dose, the formulation or the route of administration.
If you are taking iron during pregnancy, where it is the most frequent prescription of all, the constipation that follows has causes that add up and levers that are not on the plate: you will find them in what really works against constipation in pregnancy.
Anaemia in athletes: when sport is what creates the problem
In endurance athletes the relationship between anaemia and exercise is reversed: it is not anaemia that limits training, it is training that can contribute to anaemia. And in part it is not even true anaemia.
So-called "sports anaemia" is largely considered a phenomenon of dilution and blood redistribution: endurance training increases the liquid part of the blood, and the measured haemoglobin is lower for the same number of red blood cells. This is why a value slightly below the threshold in a well-trained athlete should be interpreted, not treated on instinct.
Alongside this, however, there are real losses. The narrative review on anaemia in sport lists the routes by which iron is lost during exercise: sweating, haematuria, gastrointestinal bleeding, inflammation, and intravascular and extravascular haemolysis. To these are added increased demands, dietary restrictions and reduced absorption; the authors also point out that coeliac disease, more frequent in female athletes, may explain an iron deficiency that is otherwise unexplained.
Two practical indications, both from the same source:
- Those at greatest risk, namely female athletes, adolescents, and sports with dietary restrictions, should have their iron status checked (haemoglobin and ferritin are simple, widely available tests), because correcting it can improve iron balance and perhaps also performance.
- Athletes at risk of deficiency should favour activities of low intensity and without impact on the body, such as swimming, cycling, and water-based work, precisely so as not to encourage haemolysis.
One clarification that applies to everyone, athletes included: a low value in a man or in a woman after menopause is never dismissed as "it's the sport". The routes above explain part of the picture, not all of it.
Where physiotherapy fits in
A physiotherapist does not treat anaemia: that is the job of the doctor who has your test results. In the relationship between anaemia and exercise, our piece is a different one. What we can do is the part that is usually left uncovered: build a sustainable programme with the margin you have today, act as a thermometer for progression, and gradually bring you back to your previous level once the values have settled, without the two classic mistakes (stopping completely for months, or restarting from where you left off). In telerehabilitation this works well, because what is needed is frequent check-ins more than hands-on work.
In summary
The relationship between anaemia and exercise is simpler than it is made out to be, provided one overpromise is removed. Moving with mild anaemia is generally possible and useful, but when the cause is iron deficiency it is not training that raises haemoglobin: in the reviews it is iron, and correcting the deficiency is what restores breath and performance. Movement serves to maintain what you have while the cause is being treated, with low intensity, slow progression, and a clear list of symptoms at which you stop. And if the low value has no explanation yet, that explanation comes before any training programme.
If you want to understand how to dose activity in your case, or how to return after a period of stopping, the physiotherapists at Ri-Hub can assess your situation and build the programme with you, entirely online.
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Sources
- Daily iron supplementation for improving anaemia, iron status and health in menstruating women, Cochrane Database of Systematic Reviews, 2016
- Iron supplementation benefits physical performance in women of reproductive age: a systematic review and meta-analysis, The Journal of Nutrition, 2014
- Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials, BMJ Open, 2018
- British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults, Gut, 2021
- Haemoglobin thresholds to define anaemia from age 6 months to 65 years: estimates from international data sources, The Lancet Haematology, 2024
- Anemia in Sports: A Narrative Review, Life, 2021
- Combined aerobic and resistance exercise in maintenance hemodialysis patients: A meta-analysis, Seminars in Dialysis, 2023
Last check of the sources: August 2026.
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