Iron deficiency anaemia: how to treat it and feel better

Fatigue that will not lift with sleep, breathlessness climbing the stairs, a pale tongue, cold hands, restless legs at night, brittle nails, thinning hair, and a low mood that sits on the chest: iron deficiency anaemia wears many disguises, and most of them are dismissed as "just being tired".

In UK primary care it is one of the most common treatable diagnoses, particularly in menstruating women, pregnant women, and older adults.

It is also one of the most under-treated, because the symptoms creep in slowly and because iron tablets have a reputation for side effects that puts people off.

The good news is that modern UK practice has become more flexible, and most people can be fully restored with the right regimen.

What is actually happening

Haemoglobin is the iron-containing protein in red blood cells that carries oxygen. When iron stores fall, the bone marrow cannot make enough haemoglobin, and red cells become smaller (microcytic) and paler (hypochromic). Before anaemia appears on a blood test, iron stores (measured by ferritin) fall. This "iron deficiency without anaemia" stage still causes fatigue, hair shedding, poor concentration, and restless legs, and is worth treating on its own merits. The NHS overview and Patient.info leaflet are good lay starting points.

Why it matters to know the cause

Iron deficiency is a diagnosis, not a final answer. The next question is always: why? Common causes in UK practice:

• Blood loss: heavy menstrual periods, gastrointestinal bleeding (ulcers, polyps, cancer, haemorrhoids), frequent blood donation.
• Reduced intake: vegetarian or vegan diets without planned iron sources, restrictive eating, poverty.
• Reduced absorption: coeliac disease (test everyone), Helicobacter pylori infection, atrophic gastritis, bariatric surgery, long-term PPI use.
• Increased demand: pregnancy, breastfeeding, growth spurts, endurance athletes.

UK guidance is clear: any man, or any postmenopausal woman, with iron deficiency should be investigated for gastrointestinal bleeding unless there is a clear alternative explanation.

This usually means upper and lower endoscopy.

In premenopausal women with heavy periods, a clinical history plus coeliac serology is often sufficient first line, with endoscopy reserved for non-responders or those with GI symptoms.

How it is diagnosed

A full blood count shows a low haemoglobin and a low mean cell volume (MCV). A low ferritin confirms iron deficiency: under 30 micrograms per litre is the UK threshold, though many guidelines now use under 45 in the presence of inflammation because ferritin is an acute phase reactant and can be falsely normal when CRP is raised. Transferrin saturation under 20 percent supports the diagnosis. The BNF treatment summary outlines the full diagnostic and treatment pathway.

Oral iron: how to take it so you actually absorb it

First-line UK treatment is oral ferrous sulfate 200 mg (equivalent to 65 mg elemental iron) once daily, ferrous fumarate 210 mg, or ferrous gluconate 300 mg. There are several important modern refinements that improve both tolerability and effectiveness.

Once daily is usually enough

Older regimens prescribed ferrous sulfate three times a day.

Recent trial evidence shows that iron absorption is actively suppressed for the 24 hours after a dose by rising hepcidin.

Taking iron once daily, or even once every other day, gives better cumulative absorption with far fewer side effects.

If your GP still prescribes three times daily, it is reasonable to ask about alternate-day dosing, particularly if side effects are a problem.

Timing and food

• Take iron on an empty stomach when possible (one hour before food or two hours after) with a glass of orange juice or another source of vitamin C. Vitamin C roughly doubles absorption.
• Avoid taking iron with tea, coffee, milk, calcium supplements, or antacids, which reduce absorption dramatically. Separate them by at least two hours.
• If an empty stomach causes nausea, take with a small non-dairy snack. Better to absorb some iron than give up altogether.

Managing side effects

Constipation, black stools, nausea, and metallic taste are common. Black stools are expected and harmless; they do not indicate bleeding. For constipation, macrogol or a bulk-former helps.

If nausea is limiting, switching preparation (sulfate to fumarate to gluconate) often helps because the elemental iron content differs.

Liquid ferrous sulfate is an option for those who cannot swallow tablets. Alternate-day dosing is the most reliable tolerability fix.

Expected response

Haemoglobin should rise by about 20 g/L over three to four weeks. Repeat bloods are usually done at four weeks to confirm response.

Treatment then continues for at least three months after the haemoglobin normalises, to replenish iron stores. Stopping early is a common cause of recurrence.

When oral iron is not enough

Intravenous iron (ferric derisomaltose, ferric carboxymaltose) is used when oral iron is not tolerated, not absorbed (coeliac disease, inflammatory bowel disease, post-bariatric surgery), not effective fast enough (pregnancy close to term, pre-operative optimisation), or when ongoing losses outpace absorption.

Modern IV iron preparations are given as one or two infusions and are safe in most patients.

Anaphylaxis is very rare but is the reason it is always given in a monitored setting.

Pregnancy

Pregnancy roughly doubles iron requirements.

UK practice treats ferritin under 30 at booking, and at any stage if the haemoglobin falls below the trimester threshold (110 in first trimester, 105 in second and third).

IV iron is increasingly used in the third trimester where oral iron has failed, to reduce the risk of needing transfusion at delivery.

Heavy menstrual bleeding

You cannot meaningfully replete iron if you are still bleeding heavily every month. Tranexamic acid during periods, the levonorgestrel intrauterine system (Mirena), or the combined oral contraceptive pill all reduce menstrual loss substantially. Treating the cause and the consequence together gives far better results than iron tablets alone. This overlaps with our women's health category.

Diet: genuinely helpful, but rarely enough on its own

Diet supports treatment and prevents recurrence, but is usually not sufficient to correct an established deficiency. Good sources:

• Haem iron (better absorbed): red meat, liver (avoid in pregnancy), dark poultry, oily fish.
• Non-haem iron: lentils, chickpeas, beans, tofu, fortified breakfast cereals, dark leafy greens, dried apricots, pumpkin seeds.
• Pair plant iron with vitamin C at the same meal (peppers, citrus, tomatoes, berries).
• Keep tea and coffee 30 to 60 minutes away from iron-rich meals.

Browse our broader range of nutritional supplements for iron, vitamin C, and B12 alongside women's health options, within the wider gastrointestinal health context for absorption issues.

When to ask your GP to dig deeper

See a GP urgently if you have new iron deficiency with any of: change in bowel habit lasting more than six weeks, rectal bleeding, black tarry stools, unintentional weight loss, abdominal pain, vomiting, or a family history of bowel cancer.

If oral iron has not raised the haemoglobin after 4 weeks of good adherence, ask about coeliac testing (if not already done), Helicobacter pylori testing, and consideration of IV iron.

The honest summary

Iron deficiency is common, eminently treatable, and significantly undertreated.

The modern UK approach is simple: find the cause, use a tolerable oral regimen (often once daily or alternate day, with vitamin C, away from tea and calcium), continue for three months after the haemoglobin normalises, and use intravenous iron when oral cannot do the job.

Most people feel noticeably better within two to four weeks, and fully restored within three to six months. The fatigue you assumed was just life may not be.

the Prescriptsy editorial team.. This article is general medical information and does not replace personal medical advice.

Questions I am asked most often in clinic

"Why is my ferritin low when my haemoglobin is normal?"

Because ferritin falls first. Iron stores deplete before the bone marrow runs short of building material for haemoglobin.

Low ferritin with normal haemoglobin is an early warning, not a non-diagnosis. It still explains fatigue, hair shedding, brain fog, and restless legs, and it still deserves treatment.

UK guidance supports treating symptomatic iron deficiency even before anaemia appears.

"I feel fine, do I still need to take the tablets?"

Yes, usually for three months after the haemoglobin normalises.

The tablets are doing two jobs: fixing the anaemia (4 to 6 weeks) and refilling the iron stores in the liver, spleen, and bone marrow (a further 2 to 3 months).

Stopping when you feel better, but before stores are full, is the single most common cause of recurrence. The blood count catches up faster than the storage tank.

"My stools went black, should I stop?"

No. Black stools on iron are harmless and expected. They happen because unabsorbed iron reacts in the gut.

Black, tarry, and foul-smelling stools without iron treatment can indicate upper gastrointestinal bleeding, but on iron therapy they are a normal finding.

Tell your GP you are taking iron if a stool test is ever requested.

"What if oral iron gives me terrible side effects?"

First, switch to alternate-day dosing. This alone fixes most tolerability problems.

Second, try a different iron salt: if ferrous sulfate is harsh, ferrous fumarate or ferrous gluconate often sits more comfortably.

Third, consider liquid iron or iron in water (Spatone) at a lower elemental dose.

Fourth, ask about intravenous iron, which is increasingly accessible in the UK and typically given as one or two infusions.

"Can I take iron alongside my coffee?"

Not if you want it to work well. Polyphenols in tea and coffee bind iron and reduce absorption by up to 60 percent.

Keep your iron tablet at least one hour away from tea, coffee, milk, and calcium supplements.

Many patients find that taking iron first thing with a glass of orange juice, then having breakfast 45 minutes later, works well.

"Is menstrual iron loss really enough to cause anaemia?"

It can be, easily.

Heavy menstrual bleeding (needing to change a pad or tampon every hour or two, flooding, passing clots larger than a 10p coin, or bleeding that lasts more than 7 days) loses iron faster than a normal diet can replace.

If you soak through protection, bleed through clothing, or avoid activities because of flow, that counts as heavy.

Tranexamic acid, the Mirena coil, or the combined pill can roughly halve monthly loss, and the anaemia usually resolves within 3 to 6 months once bleeding is controlled and iron replaced.

A sample restoration plan

1. Week 1: start ferrous sulfate 200 mg once daily on an empty stomach with orange juice, at least one hour before food and two hours away from tea, coffee, milk, and calcium. If nausea is a problem, take with a small non-dairy snack.
2. Weeks 2 to 4: continue daily dosing. Address any constipation with macrogol. Investigate the cause: heavy periods, diet, coeliac serology, Helicobacter testing, or endoscopy as age and history dictate.
3. Week 4: repeat full blood count and ferritin. Haemoglobin should have risen by around 20 g/L. If it has not, review adherence, recheck coeliac status, and consider intravenous iron.
4. Months 2 to 4: continue oral iron, now potentially alternate-day to reduce side effects and improve net absorption. Address the underlying cause in parallel.
5. Month 4 to 6: repeat ferritin. Once stores are above 50 micrograms per litre and symptoms have resolved, stop supplementation and plan a dietary maintenance strategy.

Dietary patterns that keep iron stable

Once you are replete, the goal is to maintain stores without daily tablets. Aim for a portion of iron-rich food at most meals, paired with vitamin C.

A working week might include lentil and vegetable soup at lunch with a squeeze of lemon, wholegrain toast with peanut butter and a glass of orange juice at breakfast, a grilled steak with dark leafy greens twice a week, and a bowl of iron-fortified cereal with strawberries on rest days.

Pumpkin seeds sprinkled on salads or yoghurt are a small but useful top-up.

Vegan and vegetarian patients need slightly more planning but reach the same endpoint, and a dietitian can help structure this.

One last word

Iron deficiency is often framed as a minor finding on a blood test. It is not.

It is a genuine cause of fatigue, reduced exercise capacity, impaired concentration, and reduced quality of life, and it is eminently treatable.

If you have been told your "iron is a bit low" and sent away with a shrug, ask specifically what your ferritin is, what the suspected cause is, and what the treatment plan is.

You deserve all three.