Sleeping eight hours and still dragging yourself through the day? Iron deficiency tiredness is one of the most common, and most commonly missed, explanations, especially for women who menstruate. Low iron means your body struggles to make haemoglobin and to supply oxygen to your muscles and brain, and fatigue can set in well before a standard blood count flags anaemia. The fix starts with a proper test, not a guess.

How does iron deficiency cause tiredness?

Iron is the core of haemoglobin, the protein in red blood cells that carries oxygen from your lungs to every tissue. It's also part of myoglobin in muscles and many enzymes involved in producing energy inside cells. When iron runs low, your body first draws down its stores (measured as ferritin). Only later does haemoglobin fall, at which point you have iron-deficiency anaemia.

Fatigue can appear at both stages. That's why many people are told their blood test is "fine" while still feeling flat. A 2012 randomised trial in the Canadian Medical Association Journal (Vaucher and colleagues) studied 198 menstruating women with unexplained fatigue, normal haemoglobin and ferritin below 50 µg/L. After 12 weeks, fatigue fell by about 48% in those taking iron versus about 29% on placebo. Not everyone responds, but it's strong evidence that low stores alone can matter.

What are the signs of iron deficiency?

Tiredness is the headline symptom, but it rarely travels alone. Watch for:

• Fatigue that sleep doesn't fix, and lower exercise tolerance
• Breathlessness or a pounding heart on stairs you used to take easily
• Pale skin, pale inner eyelids
• Headaches and difficulty concentrating
• Cold hands and feet, even outside the office aircon
• Brittle or spoon-shaped nails, and increased hair shedding
• Restless legs in the evening
• Cravings for ice or non-food items (called pica)

Many of these overlap with poor sleep, stress, thyroid problems and more, which is exactly why testing beats guessing. If your low energy tends to hit mid-afternoon rather than all day, other factors may be at play; see why energy crashes after lunch.

Who is most at risk?

• Women with periods, especially heavy ones. Their daily needs are more than double those of men.
• Pregnant women, whose iron needs rise significantly.
• Vegetarians and vegans, because plant iron is less well absorbed.
• Regular blood donors and endurance athletes.
• People with gut conditions such as coeliac disease or inflammatory bowel disease, or those who've had stomach surgery.
• People who regularly take painkillers such as aspirin or ibuprofen, which can cause slow bleeding in the gut.

Important: in men and in women after menopause, iron-deficiency anaemia is not normal and should always be investigated by a doctor, as it can be a sign of hidden bleeding in the digestive tract.

How much iron do you need?

According to the NIH Office of Dietary Supplements, adult men need about 8 mg a day, women aged 19–50 need 18 mg, women over 50 need 8 mg, and pregnant women need 27 mg. Because plant-based iron is absorbed less efficiently, vegetarians are advised to aim for about 1.8 times these amounts.

Absorption is the real story. Your body absorbs roughly 14–18% of the iron from a mixed diet that includes meat, but only about 5–12% from a vegetarian diet. Iron from meat, poultry and fish (heme iron) is absorbed much more readily than the non-heme iron in plants, eggs and fortified foods.

Which foods are high in iron?

Is your teh tarik blocking your iron?

Quite possibly. Polyphenols in tea and coffee bind to non-heme iron in the gut, and studies have found that drinking tea with a meal can cut iron absorption substantially, in some experiments by more than half. Calcium, including the condensed milk in your teh tarik, also competes with iron. The classic Malaysian breakfast of nasi lemak and teh tarik is, from an iron point of view, almost designed to underperform.

Simple fixes:

1. Move tea and coffee to at least an hour before or after iron-rich meals.
2. Add vitamin C to plant-based meals: a squeeze of calamansi, guava or orange, tomato, or capsicum. Vitamin C can multiply non-heme iron absorption. We cover this in our guide to vitamin C and iron absorption.
3. Pair plant iron with a little heme iron: meat, poultry or fish in the same meal boosts absorption of the plant iron too.
4. Don't skip protein-rich lauk in favour of extra rice. Our look at protein in Asian diets shows why this helps on several fronts.

Should you take an iron supplement?

If you have diagnosed iron deficiency, your doctor will likely prescribe iron at a treatment dose, often for three months or more, and recheck your levels. Newer research (Stoffel and colleagues, Lancet Haematology, 2017) suggests taking iron on alternate days may improve absorption and reduce stomach side effects, so ask your doctor whether that's appropriate for you. Common side effects include constipation, nausea and dark stools.

Without a diagnosis, high-dose iron is not a good idea. Here's the Southeast Asian twist: thalassaemia trait is common in Malaysia and the region, and it produces small, pale red blood cells that look like iron deficiency on a basic blood count. Extra iron doesn't help thalassaemia and can build up to harmful levels. The same applies to haemochromatosis, a genetic iron overload condition. The adult upper limit for iron from supplements and food is 45 mg a day unless a doctor advises otherwise, and iron supplements must be kept away from children, for whom an overdose can be dangerous.

For everyday topping-up alongside a good diet, a lower-dose daily product is a gentler option. TANO's THRIVE effervescent greens includes iron together with vitamin C, which helps absorption, in a Crisp Apple drink. It contributes to your daily intake but isn't a treatment for deficiency; if your ferritin is low, follow your doctor's plan.

How to get tested

1. See a GP or your local klinik kesihatan and describe your symptoms, including how long they've lasted and your periods, diet and any bleeding.
2. Ask for a full blood count and serum ferritin. The WHO uses ferritin below 15 µg/L to define depleted stores in adults; many clinicians consider below 30 µg/L suggestive of deficiency in someone with symptoms.
3. If your red cells are small but ferritin is normal, ask whether thalassaemia screening is appropriate.
4. Recheck after treatment to confirm your levels have recovered.

This article is general information, not medical advice. Please see a doctor for testing before taking iron supplements, particularly if you are pregnant, have a blood disorder such as thalassaemia, a gut condition, or are on other medication.

Frequently asked questions

Can low iron make you tired even if you're not anaemic?

Yes. Iron stores (ferritin) can be low while haemoglobin is still normal, and research in menstruating women found iron supplements reduced fatigue in this group. Ask your doctor for a ferritin test, not just a full blood count.

How long does it take to feel better after starting iron?

Many people notice improved energy within a few weeks, and haemoglobin typically rises within about a month of treatment. Rebuilding iron stores takes longer, often three months or more, so it's important to follow your doctor's plan and recheck your levels.

Does drinking tea or coffee affect iron absorption?

Yes. Polyphenols in tea and coffee can substantially reduce absorption of non-heme iron from plant foods when consumed with meals. Having them at least an hour away from iron-rich meals helps.

What is the best way to take iron supplements?

Take them as your doctor directs, ideally with a source of vitamin C and away from tea, coffee, dairy and calcium supplements. Some evidence suggests alternate-day dosing improves absorption and tolerability, so ask whether that suits you.

Can you take too much iron?

Yes. The upper limit for adults is 45 mg a day unless prescribed, and excess iron can cause stomach upset and, over time, organ damage in people with iron overload conditions. Accidental iron overdose is especially dangerous for young children, so store supplements safely.

Sources

1. NIH Office of Dietary Supplements: Iron fact sheet for health professionals
2. World Health Organization: Anaemia fact sheet
3. NHS: Iron deficiency anaemia
4. Mayo Clinic: Iron deficiency anemia
5. Vaucher et al. (2012). Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin. CMAJ