Iron Deficiency Symptoms — Is This Why You're Exhausted?
You thought it was just tiredness. That you weren't sleeping well, or working too hard, or that this is simply what getting older feels like. But the exhaustion doesn't lift. Your hair is thinning. You can't think clearly. You're breathless on the stairs. If this sounds like you, it might not be in your head — it might be in your blood.
What is iron deficiency?
Iron deficiency means your body's iron stores have been depleted to the point where normal functions are affected. Iron is essential for producing haemoglobin — the molecule in red blood cells responsible for carrying oxygen from your lungs to every cell in your body.
When iron runs low, oxygen delivery suffers. Your muscles tire faster. Your brain struggles to concentrate. Your heart works harder to compensate. Hair follicles don't get the nutrients they need. Over time, every system in your body feels the impact — which is why iron deficiency symptoms are so wide-ranging, and why so many people assume there must be multiple things wrong, rather than one underlying cause.
In the UK, iron deficiency is the most common nutritional deficiency — affecting around 1 in 5 women of reproductive age, according to NHS data. The British Society for Haematology notes that symptoms can appear well before ferritin levels drop low enough to meet the technical threshold for anaemia. In other words: you can feel terrible and still be told your results are "normal."
Signs and symptoms of iron deficiency
Iron deficiency affects your whole body. These are the most common symptoms — you don't need all of them. Even two or three together are worth investigating.
Energy & Cognition
Relentless fatigue
Not ordinary tiredness — an exhaustion that sleep doesn't fix. You wake up drained and get worse through the day.
Brain fog
Difficulty concentrating, forgetting words mid-sentence, struggling with tasks that used to be easy. Many people describe it as thinking through cotton wool.
Low motivation and mood changes
Iron is involved in producing serotonin and dopamine. Low iron can contribute to irritability, low mood, and a feeling of emotional flatness.
Heart & Lungs
Breathlessness on mild exertion
Getting winded climbing stairs, walking uphill, or during light exercise. Your body doesn't have enough iron to carry oxygen efficiently.
Heart palpitations
Your heart has to work harder to circulate oxygen when iron is low. This can feel like fluttering, pounding, or an irregular heartbeat — even at rest.
Dizziness and light-headedness
Standing up too quickly and feeling faint, or ongoing dizziness throughout the day. Reduced oxygen delivery to the brain is a direct consequence of low iron.
Hair, Skin & Nails
Hair thinning and hair loss
More hair on your brush, in the shower, on your pillow. Iron deficiency disrupts the hair growth cycle, causing increased shedding (telogen effluvium). This is reversible once iron is restored.
Pale skin, lips, and inner eyelids
Haemoglobin gives blood its red colour. When iron is low, reduced haemoglobin makes skin, gums, lips, and the inside of your lower eyelids look noticeably pale.
Brittle or spoon-shaped nails
Nails that chip, crack, or develop a concave shape (koilonychia) are a classic sign of iron deficiency. The nail bed doesn't receive enough iron to grow normally.
Dry, cracked skin or mouth sores
Angular cheilitis — painful cracks at the corners of your mouth — and unusually dry skin can both be signs of iron deficiency.
Other Symptoms
Restless legs
An irresistible urge to move your legs, especially at night. Iron deficiency is one of the most common reversible causes of restless legs syndrome.
Frequent infections
Iron supports immune function. When stores are low, you may catch colds more often or find that wounds heal slowly.
Cold hands and feet
Poor oxygen delivery to your extremities means you feel cold when others are comfortable — even in warm rooms.
Unusual cravings (pica)
Craving ice, dirt, chalk, or starch. Pica is a well-documented symptom of iron deficiency — though the exact mechanism isn't fully understood.
Headaches
Recurrent headaches, particularly with exertion. Reduced oxygen to the brain triggers the pain response.
Swollen or sore tongue
A smooth, swollen, or pale tongue (glossitis) is caused by low iron affecting the tissue. It can make eating and speaking uncomfortable.
Sound familiar? If you recognise three or more of these symptoms, iron deficiency is worth investigating. A simple blood test can confirm it.
Check Symptoms + Get Free PlanWhy iron deficiency causes so many symptoms
Iron isn't just about energy. It's involved in oxygen transport, neurotransmitter production, immune function, collagen synthesis, and cellular energy metabolism. When iron is depleted, all of these processes are affected — which is why the symptoms are so varied and why they're often mistaken for other conditions.
Your body prioritises survival. When iron stores drop, it redirects what little iron remains to essential functions like making red blood cells — and "non-essential" systems like hair growth, nail strength, and cognitive sharpness suffer first. This is why you might notice hair loss and brain fog months before a blood test shows anything abnormal.
Many people try oral iron supplements and give up. The side effects — constipation, nausea, stomach cramps — are significant, and only 10–20% of the iron is absorbed in the first place. If the underlying cause of your deficiency is still present (such as heavy periods or a malabsorption condition), oral iron may never be enough to catch up.
That's the frustrating cycle: you feel awful, you take tablets that make you feel worse, your levels barely move, and eventually you stop trying. It doesn't have to be that way.
What can you do about it?
Dietary changes
Eating more iron-rich foods — red meat, liver, lentils, dark leafy greens — helps maintain levels. Pairing iron-rich foods with vitamin C improves absorption.
Helpful for prevention, but unlikely to correct an established deficiency on its own.
Oral iron supplements
Ferrous sulphate or ferrous fumarate — the standard GP prescription. Needs to be taken daily for 3–6 months.
Works for some, but up to 70% of people experience side effects. Only 10–20% of the iron is absorbed. Not suitable if you have gut absorption issues.
IV iron infusion
Up to 1000mg of iron delivered directly into your bloodstream in a single 30-minute session. Bypasses the gut entirely.
NICE-recommended when oral iron hasn't worked, isn't tolerated, or when iron levels need restoring quickly. Most patients feel improvement within 1–2 weeks.
How IronOx Clinic helps
If the symptoms on this page sound like your life, the first step is finding out whether iron deficiency is the cause. That starts with a proper assessment — not a five-minute GP appointment where you're told to eat more spinach.
At IronOx Clinic, Dr Ros reviews your symptoms alongside your blood results — looking at your ferritin, transferrin saturation, full blood count, and the clinical picture as a whole. Many patients come to us after being told their levels are "fine" by their GP, only to find that their ferritin is well below the threshold where symptoms begin.
If iron deficiency is confirmed, you'll understand exactly what's causing it and which treatment is right for you. If an infusion is appropriate, it can often be done in the same visit — so you leave with the treatment, not just another referral.
What you get
- Specialist consultation with Dr Ros
- Full blood picture review, not just ferritin
- Same-week appointments available
- No GP referral needed
- Treatment in the same visit if appropriate
- GP report within 24 hours
"I thought I was just getting old"
"For eighteen months I was exhausted, foggy, and losing hair. My GP tested my iron and said it was 'within range' at 18. I'd almost accepted that this was just life now. A friend suggested I see a specialist. Dr Ros looked at my results and immediately said my ferritin was far too low for someone with my symptoms. I had an infusion that day. Two weeks later, the fog lifted. My energy came back. My hair stopped falling out. I genuinely didn't realise how bad I'd been feeling until I felt normal again."
Iron deficiency symptoms — your questions answered
Yes. Many people experience symptoms of iron deficiency even when their GP says results are 'normal'. This often happens because ferritin levels between 15 and 30 µg/L are technically within the reference range — but low enough to cause fatigue, brain fog, and hair loss. A specialist assessment looks at the full picture, not just whether your number falls inside a lab range.
Ordinary tiredness improves with rest. Iron deficiency fatigue doesn't — no matter how much you sleep, you still feel drained. It's often accompanied by other symptoms: brain fog, breathlessness on stairs, hair falling out more than usual, or feeling cold when others are comfortable. If multiple symptoms on this page sound familiar, it's worth getting your iron levels checked.
Iron deficiency develops gradually over weeks or months, and so do the symptoms. Most people don't notice a sudden change — instead, they slowly adapt to feeling worse. This is why many people live with iron deficiency for months or years before seeking help. They've forgotten what 'normal' feels like.
Iron plays a role in neurotransmitter production, including serotonin and dopamine. Research shows an association between iron deficiency and increased rates of anxiety and depression — though it's important not to assume iron is the only factor. If you're experiencing mood changes alongside physical symptoms of iron deficiency, it's worth having your levels assessed as part of a broader clinical picture.
Start with a blood test. You can ask your GP for a full blood count and ferritin level, or you can book directly with IronOx Clinic — no referral needed. If you have recent blood results (within 3 months), bring them to your appointment. A specialist assessment will tell you whether iron deficiency is likely and what treatment is most appropriate.
Medically reviewed by Dr Ros Jabar, GMC-registered doctor and Medical Director at IronOx Clinic. Last reviewed May 2026.
Stop wondering. Find out.
If these symptoms describe your life, a specialist assessment can tell you whether iron deficiency is the cause — and what to do about it. No referral needed.