Exercise guide
Anaemia means your blood carries less oxygen, so you tire sooner, get breathless more easily and can't do as much. Iron deficiency anaemia is the most common type, often caused by heavy periods, pregnancy or bleeding in the gut, and athletes, especially women and endurance runners, are often low in iron even before they become anaemic.
This guide covers exercising with anaemia, building back up as treatment works, and iron in athletes and runners, with 3D demos of gentle moves. One rule runs through it: don't take iron supplements without a blood test, because iron only helps if you're low and too much can build up. Call 999 if you have chest pain or faint while exercising.
Anaemia means your blood has less haemoglobin, the protein in red blood cells that carries oxygen, so you tire sooner and get breathless more easily. Iron deficiency anaemia is the most common type. Its symptoms include tiredness, shortness of breath, a pounding or fluttering heartbeat (palpitations) and pale skin.
A blood test shows whether you're anaemic and low in iron. In men and in women after the menopause, about a third have an underlying cause, usually in the gut, so your GP (general practitioner) will look for it. The National Institute for Health and Care Excellence (NICE) says to offer a blood count to anyone with heavy periods.
Iron only helps if you're low. Taken when you don't need it, it can cause side effects and build up over time: in one study, 1 in 6 male marathon runners had too much iron. People with haemochromatosis, an inherited iron overload, are advised not to take iron supplements.
No UK guideline sets exercise rules for anaemia. Anaemia lowers how much you can do, so keep activity easy and build up as your treatment works. Our reading: if you're breathless, dizzy or exhausted with light activity, see your GP before exercising.
Low iron affects 15% to 35% of female and 5% to 11% of male athletes. Periods, eating too little for your training, sweat, foot strike and a hormone that blocks iron absorption for a few hours after long sessions all play a part. When athletes are low, treating it improved endurance and fitness in small studies.
Call 999 for chest pain that feels tight or spreads to your arms, neck or jaw, if you faint while exercising, or if you vomit blood and feel faint or have black poo. Black or dark red poo needs an urgent GP appointment or NHS 111.
Anaemia is when your haemoglobin, or your number of red blood cells, is lower than normal. The World Health Organization (WHO) calls iron deficiency the most common nutritional cause of anaemia, and the British Society of Gastroenterology (BSG) says iron deficiency anaemia is the most common anaemia seen in UK general practice. Other types come from a lack of vitamin B12 or folate, or from inherited conditions such as thalassaemia and sickle cell disease.
A full blood count measures your haemoglobin. WHO counts anaemia as under 130 grams per litre for men and under 120 for women who aren't pregnant, with lower cut-offs in pregnancy; labs set their own ranges. Ferritin shows your iron stores: under 15 micrograms per litre means they're empty and under 30 that they're low, but inflammation can raise ferritin and hide a deficiency.
You can be low in iron (low ferritin) while your haemoglobin is still normal. This is iron deficiency without anaemia, and in trials, treating it eased tiredness.
Tiredness and lack of energy, shortness of breath, palpitations and pale skin are the main symptoms; headaches, ringing in the ears, a sore tongue, hair loss, mouth ulcers, spoon-shaped nails, restless legs and craving ice or other non-food things can happen too. WHO lists reduced capacity for physical work and breathlessness "especially upon exertion". Mild anaemia may cause no symptoms at all.
Worldwide, about 30% of women aged 15 to 49 have anaemia. In countries like the UK, iron deficiency anaemia affects 5% to 12% of women before the menopause, and 2% to 5% of men and of women after it.
Your muscles get less oxygen, so the same effort feels harder. A review of 29 reports found that moderate and severe iron deficiency anaemia reduces aerobic capacity and endurance, and in female athletes, low iron was linked with a few per cent lower endurance performance. In heart failure, exercise capacity is lowest when anaemia and low iron come together.
Heavy periods and pregnancy are very common causes. Others include bleeding in the stomach or gut (from anti-inflammatory painkillers such as ibuprofen and aspirin, stomach ulcers, inflammation or piles, and less often bowel or stomach cancer), coeliac disease, not getting enough iron from food, giving blood, and long-term use of some stomach-acid medicines (proton pump inhibitors).
About a third of men and of women after the menopause with iron deficiency anaemia have an underlying cause, mostly in the gut, which is why your GP will investigate. NICE recommends a home poo test (a faecal immunochemical test) for adults with iron deficiency anaemia, and for anyone aged 60 or over with anaemia. In women before the menopause, periods are the usual cause, though coeliac disease is often checked too.
The International Olympic Committee (IOC) lists low or poorly absorbed iron, eating too little for your training, growth, altitude, periods, foot strike, and iron lost in sweat, urine and poo. Hepcidin, a hormone that blocks iron absorption, peaks 3 to 6 hours after exercise, mainly after long sessions, and foot strike breaks some red blood cells: in 10 triathletes, running released 4 times more haemoglobin into the blood than cycling did.
Most of the research is in athletes and in women with heavy periods. There are no trials of exercise programmes for people with anaemia.
A critical review of 29 reports concluded that moderate and severe iron deficiency anaemia causes lower aerobic capacity and endurance, and that low iron reduces how efficiently you work at any level. WHO lists reduced physical work capacity among anaemia's symptoms.
In iron-deficient female athletes (23 studies, 669 athletes), iron improved endurance performance by 2% to 20% and fitness by 6% to 15%, though the groups were small. In endurance athletes low in iron without anaemia (17 studies), iron raised iron stores, haemoglobin and fitness. In active women, iron tablets raised haemoglobin and ferritin a little.
In adults low in iron without anaemia (18 trials, 1,170 people), iron eased tiredness modestly but didn't improve measured exercise capacity overall. In 198 menstruating women with low ferritin and unexplained tiredness, 12 weeks of iron reduced tiredness more than a dummy pill (by 48% against 29%).
The IOC says high-dose iron "should not be taken unless iron deficiency is present", and Swiss sports physicians say long-term iron with normal or high ferritin "does not make sense and may be harmful". In 170 recreational marathon runners, 15% of the men had too much iron.
No trial shows that exercise treats iron deficiency anaemia: treatment means finding the cause and replacing iron. Endurance training expands the liquid part of the blood (plasma), which dilutes haemoglobin a little. This "sports anaemia" isn't true anaemia.
The NHS and NICE don't set exercise rules for anaemia. WHO describes reduced capacity for physical work and breathlessness that's worse with effort, so expect exercise to feel harder until treatment works.
If you're breathless, dizzy or exhausted with light activity, see your GP before exercising, and build up as your treatment works. This is our reading of the guidance, not a rule from a guideline. The NHS says to see a GP if your breathlessness gets worse when you're doing your normal activities.
Our editorial starting point while you're being treated: easy activity you can talk through in full sentences, such as walking or cycling, in shorter sessions with a longer warm-up and cool-down, plus light strength work on 2 days a week. Get up slowly if you feel light-headed, because dizziness on standing can come with anaemia. Stop for chest pain, palpitations, dizziness, or breathlessness that's out of proportion to what you're doing.
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With kidney disease, heart failure, inflammatory bowel disease or sickle cell disease, anaemia is managed by your specialist team: follow their advice, and see our guides for those conditions. Our pregnancy guide covers anaemia in pregnancy.
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Once the cause has been found (for example, an ulcer or heavy periods), your GP will recommend treatment. Iron treatment usually starts while tests are still under way.
If your blood test shows iron deficiency anaemia, your GP will recommend iron tablets. The BSG recommends one tablet a day, or one every other day if you can't tolerate that, with a check on your blood count within the first 4 weeks.
The NHS says you'll need to take iron tablets for about 6 months. The BSG says to carry on for about 3 months after your haemoglobin is back to normal, to refill your stores, and the US National Heart, Lung, and Blood Institute (NHLBI) says it often takes 3 to 6 months. Follow your GP's advice, and go back for your repeat blood tests.
Iron tablets can cause constipation or diarrhoea, tummy pain, heartburn, feeling sick and darker poo. Taking them with or soon after food can help. The NHS says to keep taking them even if you get side effects; talk to your GP if they're a problem.
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The NHS says drinking orange juice after a tablet may help your body absorb the iron. The BSG says taking vitamin C with iron tablets isn't recommended, because a large trial found it didn't help. Follow your GP's advice.
If diet is part of the cause, the NHS suggests more dark-green leafy vegetables, cereals and bread with added iron, meat, dried fruit and pulses, and less tea, coffee, milk and dairy, and wholegrain cereals, which in large amounts make iron harder to absorb. Most people can get all the iron they need from a varied diet.
If tablets don't work, can't be taken, or you need iron quickly, it can be given through a drip into a vein (intravenous iron).
A rise in haemoglobin of 10 grams per litre or more within 2 weeks shows the iron is working, and your GP will check your response within about 4 weeks. Refilling your iron stores takes months.
This is our suggestion, not a guideline:
Recheck your iron with your doctor after a course of treatment. Swiss sports physicians suggest elite athletes have their iron checked twice a year.
Iron improves energy and performance only when you're low. The IOC says high-dose iron should not be taken unless a deficiency is present, and in one study 1 in 6 male recreational marathon runners already had too much iron. Ask your GP for a blood test first.
High doses (over 20 mg) can cause constipation, sickness and stomach pain, and iron taken without need can build up and damage the liver. The NHS says taking 17 mg or less a day from supplements is unlikely to cause harm, and to take a higher dose only if a GP advises it. Keep iron tablets out of children's reach: an overdose can be fatal for a young child.
Haemochromatosis is an inherited condition in which iron builds up and can damage the liver, joints, pancreas and heart. It's most common in people with a northern European or Celtic background, and people with it are advised not to take iron or vitamin C supplements.
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Carriers of thalassaemia may have mild anaemia that isn't iron deficiency and doesn't need treatment: another reason to test before taking iron.
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Reviews estimate that 15% to 35% of female and 5% to 11% of male athletes are low in iron, and up to 60% in some groups of female athletes.
The IOC recommends checking iron with ferritin and other blood tests when a deficiency is suspected. If you're tired, your performance keeps falling or your periods are heavy, see your GP for a blood test.
In UK guidance, ferritin under 15 micrograms per litre means empty iron stores and under 30 low stores. Swiss sports physicians use 30 as the cut-off for athletes over 15, and suggest 50 before altitude training for elite athletes; that is a sports medicine view, not a UK guideline. Your doctor will interpret your result.
Endurance training increases the liquid part of your blood, so your haemoglobin can read slightly low without any lack of red cells. This "is not anemia in a clinical sense", but true iron deficiency is also common in athletes, so only a blood test can tell them apart.
Relative energy deficiency in sport (REDs) happens when you don't eat enough for the training you do, and it harms health and performance in both women and men. Our women's guide covers it, and our eating disorders guide can help if eating has become difficult.
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The NHS lists:
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In surveys, heavy periods were reported by 36% of London Marathon runners, 37% of elite athletes and 54% of women answering online. A third had had anaemia, but only 22% had asked for medical advice.
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See a GP if heavy periods are affecting your life. NICE says to offer a full blood count to everyone with heavy periods, and treatments can make periods lighter. Our menstrual cycle guide covers exercise and periods.
Vitamin B12 deficiency can cause problems with balance and coordination, numbness, pins and needles and muscle weakness, which matter for exercise safety. It affects about 1 in 10 people aged 75 and over. NICE says treatment shouldn't be delayed if you have these nerve symptoms.
Thalassaemia carriers can have mild anaemia that needs no treatment. Sickle cell disease is different again, and our sickle cell guide covers exercise with it.
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Anaemia and low iron are common in these conditions: about a third of people with active inflammatory bowel disease are low in iron, and 40% to 70% of people with chronic heart failure. Your specialist team manages it, often with iron through a drip, because tablets work poorly in heart failure. Our guides for these conditions cover exercise.
Iron deficiency is common in older people and often has more than one cause. NICE recommends a home poo test for anyone aged 60 or over with anaemia, even without low iron.
Our editorial starting point: 10 to 20 minutes at an easy pace you can talk through, building as your energy returns. A seated bike is safest if you feel faint. Leave jogging until treatment is working, then use run-walk intervals.
1 to 2 short sets of 8 to 12 on 2 days a week, resting between sets (our editorial starting point). Breathe out on the effort, and get up slowly.
Start with the 10-minute starter workout or a short easy walk, and shorten any session on tired days. The run-walk sessions rebuild running once your treatment is working.
A 10-minute session for low-energy days: marching, sit-to-stands, wall push-ups, step-ups and bridges, then a short walk. Doing a little counts.
10 minBeginner7 movesA bench or box, A wallA steady 30 to 45 minute cardio session at talk-but-not-sing pace: walk, cycle, row or cross-train, counting toward weekly activity guidelines.
40 minBeginner3 movesCardio machine, A wallA 10-minute routine for straight after a meal: an easy walk, a few simple standing moves from blood sugar trials, then a short walk to finish.
10 minBeginner6 movesCardio machine, A bench or boxA 20-minute seated workout for older adults who cannot stand for long: marching, leg and arm strength, posture, and sit-to-stands that lead back to standing.
20 minBeginner11 movesA bench or box, Something with weightA gentle 20-minute beginner home workout with a chair, a wall and a band: sit-to-stands, wall push-ups, band rows, step-ups and dead bugs.
20 minBeginner11 movesA bench or box, A wallA 25-minute walk with short faster bouts: notice your heart and breathing speed up, then settle. A gentle way to get used to the feelings of effort.
25 minBeginner5 movesCardio machine, A wallA 30-minute beginner run-walk session: a brisk walk, then 1-minute jogs with 1-minute walks, building to 3-minute runs over your first three weeks.
30 minBeginner5 movesCardio machine, A wallA 40-minute walk alternating 3 minutes fast and 3 minutes easy, five times over: the interval walking tested in Japanese trials, built up from three rounds.
40 minBeginner3 movesCardio machine, A wallStart these once your treatment is working, and repeat a week whenever you need to.
A free 8-week walking plan for beginners: build to 150 minutes of brisk walking a week, with intervals, hills and two short strength sessions.
6 training days40 minBeginner3 days a weekA 9-week beginner plan with the same walk-to-run shape as Couch to 5K: three run-walk sessions a week, from 1-minute jogs to 30 minutes of running.
3 training days35 minBeginner2 days a weekYour first four weeks: two, then three short strength sessions a week at home plus walks, building gently to a full routine.
2 training days20 minBeginnerA&E means accident and emergency.
Call 999 (911 in the US) if:
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Call 999 if someone faints while exercising, faints and has chest pain or a pounding, fluttering or irregular heartbeat, can't be woken within a minute, or hasn't fully recovered. See a GP after any faint.
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Call 999 or go to A&E if you vomit blood and feel faint, dizzy or confused, have cold, clammy skin, fast or shallow breathing, tummy pain or black poo, or if bleeding from your bottom won't stop or there's a lot of blood.
The NHS warns that an overdose of iron can be fatal for a young child. If a child may have swallowed iron tablets, treat it as an emergency and call 999 (our advice).
Stop and rest if you get chest pain, palpitations, dizziness or breathlessness that's out of proportion to what you're doing, and sit or lie down if you feel faint (our suggestion). Fainting during exercise is a 999 call.
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Tiredness has many causes, and iron only helps if you're low; too much can build up, as it had in 1 in 6 male marathon runners in one study. People with haemochromatosis are advised not to take iron, and thalassaemia carriers can have mild anaemia that iron doesn't fix. Get a blood test first.
The IOC says high-dose iron shouldn't be taken unless you're deficient, and Swiss sports physicians say iron with normal or high ferritin may be harmful. Iron improved performance in athletes who were low, not in those who weren't.
No trial shows exercise treats iron deficiency anaemia. Training expands the plasma, which dilutes haemoglobin, and long, hard sessions lower iron absorption for a few hours and break some red cells through foot strike. Treatment is finding the cause and replacing iron.
It's dilution from a bigger plasma volume, "not anemia in a clinical sense". True iron deficiency is also common in athletes, so a blood test is the only way to tell.
They're common in active women but under-treated: only 22% of women in one survey had asked for advice. Treatments help, and NICE says to offer a blood count.
Vitamin B12 or folate deficiency, thalassaemia trait, sickle cell disease and kidney disease cause anaemia too, and need different treatment.
The NHS says orange juice after a tablet may help; the BSG says vitamin C isn't recommended, because a large trial found no benefit. Follow your GP's advice.
Usually yes, gently and within your symptoms, but anaemia reduces how much you can do, so expect to tire sooner and get breathless more easily. No UK guideline sets exercise rules for anaemia, so get the cause found and treated, and build up as your treatment works. Stop for chest pain, palpitations, dizziness or breathlessness that's out of proportion to what you're doing.
Not without checking first. Our reading is that if you're breathless, dizzy or exhausted with light activity, you should see your GP before exercising, and build up as your treatment works. Rest, follow your treatment, and ask your doctor when to start.
Your blood carries less oxygen, so your heart and lungs work harder to supply your muscles. WHO lists breathlessness, especially with effort, and reduced capacity for physical work among anaemia's symptoms. Being more breathless than usual, or palpitations, is a reason to contact NHS 111.
Hard endurance training can contribute to low iron: a hormone called hepcidin rises for a few hours after long sessions and blocks iron absorption, foot strike breaks some red cells, and iron is lost in sweat. Training also expands blood plasma, which dilutes haemoglobin without true anaemia ("sports anaemia"). Periods and eating too little for your training are common causes in athletes.
Not directly: no trial shows exercise treats iron deficiency anaemia, and treatment means finding the cause and replacing iron. Staying gently active while you're treated, then rebuilding, keeps you fitter for when your blood count recovers.
Haemoglobin often starts to rise within a few weeks of starting iron tablets, and treatment carries on for months to refill your stores: about 6 months in NHS advice, or about 3 months after your blood count is normal in UK specialist guidance. Our suggestion is to build back gradually as you feel better, and return to hard sessions once your blood test is back to normal.
Only if a blood test shows you're low. The IOC says high-dose iron shouldn't be taken unless you're deficient, and in one study 1 in 6 male marathon runners had too much iron. The NHS says 17 mg a day or less from supplements is unlikely to cause harm, and to take more only on a GP's advice.
UK guidance treats ferritin under 15 micrograms per litre as empty stores and under 30 as low. Swiss sports physicians use 30 as their cut-off for athletes over 15, and 50 before altitude training for elite athletes. Your doctor will interpret your result, because inflammation can push ferritin up.
It's a slightly lower haemoglobin reading in well-trained endurance athletes, caused by a bigger volume of blood plasma rather than a lack of red cells, and it isn't anaemia in a medical sense. True iron deficiency is also common in athletes, so a blood test is the only way to tell the difference.
Yes: heavy periods are a very common cause of iron deficiency anaemia. Signs of heavy periods include changing a pad or tampon every 1 to 2 hours, bleeding for more than 7 days, clots bigger than about 2.5 cm, and avoiding activities like exercise. See a GP: NICE says to offer a blood count, and treatments can make periods lighter.
Light strength work is usually fine once you're being treated, with short sets and rests between them. Breathe out on the effort, get up slowly if you feel light-headed, and leave heavy lifting until your energy is back (our suggestion).
Usually, once treatment has started, but B12 deficiency can affect balance, coordination and feeling in your feet, so take care and choose steady activities. NICE says treatment shouldn't be delayed if you have numbness, pins and needles or balance problems. See your GP if these symptoms appear.
Exercise education, not a diagnosis or treatment plan, and clinical review of these guides is pending. Stop and get advice for chest pain, unusual breathlessness, dizziness or fainting, or new pain, and check with your doctor or midwife first if they have told you to limit activity. Health disclaimer.
