Iron deficiency happens when your body’s iron stores fall below what it needs to make enough healthy red blood cells. The earliest signs are often easy to dismiss: persistent tiredness, pale skin, and a general sense of running on empty. Left unaddressed, iron deficiency can progress to iron deficiency anaemia, where a shortage of haemoglobin starts to limit how much oxygen reaches your muscles, brain and organs.
Around one in four adults may have some degree of iron deficiency, and it is one of the most common nutrient shortfalls worldwide, particularly among women of reproductive age. Because the symptoms build gradually, many people adjust to feeling below par without realising low iron is the cause.
What Is Iron Deficiency?
Iron is a mineral your body uses to build haemoglobin, the protein inside red blood cells that carries oxygen from your lungs to every tissue in your body. Iron deficiency is the stage where your stored iron, measured as ferritin, drops too low to support normal haemoglobin production. It exists on a spectrum:
- Depleted iron stores: ferritin is low but haemoglobin is still normal. Symptoms may be mild or absent.
- Iron deficiency without anaemia: ferritin is low and early symptoms such as fatigue and poor concentration appear, but haemoglobin has not yet dropped.
- Iron deficiency anaemia: both ferritin and haemoglobin are low. This is when symptoms become more noticeable and consistent.
Early Warning Signs of Iron Deficiency
The first signs of low iron are usually vague and easy to blame on a busy schedule or poor sleep. Catching them early, before anaemia develops, makes treatment faster and simpler.
| Early Signs (Mild Deficiency) | Severe Signs (Iron Deficiency Anaemia) |
|---|---|
| Low-grade tiredness that sleep does not fix | Extreme, unrelenting fatigue |
| Slightly pale skin or inner eyelids | Noticeable paleness, especially of gums and nail beds |
| Mild breathlessness on exertion | Shortness of breath with light activity |
| Occasional headaches | Frequent headaches or lightheadedness |
| Reduced concentration, mild brain fog | Difficulty focusing, memory lapses |
| Cold hands and feet | Persistent coldness and poor circulation |
| Mild restlessness in the legs at night | Restless legs syndrome that disrupts sleep |
The Full List of Iron Deficiency Symptoms
Physical Symptoms
- Fatigue and low energy, even after a full night’s sleep
- Shortness of breath, particularly during exercise or stairs
- A fast or irregular heartbeat (palpitations)
- Chest discomfort in more severe cases
- Cold hands and feet
- Headaches and dizziness
- Restless legs syndrome
Cognitive and Mental Symptoms
- Brain fog and difficulty concentrating
- Reduced productivity or work performance
- Low mood, irritability or heightened anxiety
- In some studies, symptoms overlapping with ADHD, including inattention and restlessness
Skin, Hair and Nail Symptoms
- Pale or sallow skin tone
- Brittle, thin or spoon-shaped nails
- Hair thinning or increased shedding
- A sore or unusually smooth tongue
- Cracks at the corners of the mouth
Appetite and Craving Changes
- Reduced appetite, particularly in children
- Pica: cravings to chew ice, dirt, chalk or starch
- Unusual cravings for non-food smells such as detergent or rubber
Iron Deficiency Symptoms in Women
Women are disproportionately affected by iron deficiency, largely because of monthly blood loss through menstruation, and further increased demand during pregnancy. Heavy menstrual bleeding is one of the most common underlying causes in women of reproductive age, and research has found a notable overlap between low iron, heavy periods and symptoms often mistaken for anxiety or ADHD, including racing thoughts, restlessness and difficulty focusing. If you already recognise some of these overlapping patterns, our guide to anxiety symptoms in women covers how to tell the difference between anxiety and physical causes like low iron.
What Causes Iron Deficiency?
- Blood loss: heavy periods, gastrointestinal bleeding, or frequent blood donation
- Inadequate dietary intake: low consumption of iron-rich foods, common in vegetarian and vegan diets without careful planning
- Increased demand: pregnancy, breastfeeding, adolescent growth spurts, and endurance training
- Malabsorption: coeliac disease, inflammatory bowel disease, or previous weight loss surgery, all of which reduce how much iron the gut can absorb
- Certain medications: long-term use of antacids or proton pump inhibitors, which lower stomach acid needed for iron absorption
Iron Deficiency vs Iron Deficiency Anaemia
| Feature | Iron Deficiency | Iron Deficiency Anaemia |
|---|---|---|
| Ferritin (stored iron) | Low | Low |
| Haemoglobin | Normal | Below normal range |
| Symptom intensity | Mild, easy to miss | Noticeable and persistent |
| Typical treatment | Dietary changes, sometimes low-dose supplements | Iron supplements, occasionally IV iron or transfusion |
Best Iron Rich Foods
Iron from food comes in two forms: heme iron, found in animal products and absorbed efficiently, and non-heme iron, found in plants and absorbed less efficiently unless paired with vitamin C.
| Heme Iron Sources (animal) | Non-Heme Iron Sources (plant) |
|---|---|
| Red meat and liver | Spinach and dark leafy greens |
| Poultry | Lentils and beans |
| Oily fish and shellfish | Tofu and edamame |
| Eggs | Fortified cereals and wholegrains |
| Pumpkin seeds and nuts |
Pairing plant-based iron with a source of vitamin C, such as citrus fruit, peppers or tomatoes, meaningfully improves absorption. Tea and coffee taken with meals can reduce iron absorption, so it helps to leave a gap of thirty to sixty minutes. If you are also focused on broader nutrient gaps, our guide to magnesium deficiency symptoms covers another common shortfall that shares several overlapping signs, including fatigue and restless legs.
How Iron Deficiency Is Diagnosed
A GP will usually order a full blood count alongside a ferritin test, since haemoglobin alone can miss early deficiency. Total iron-binding capacity (TIBC) and transferrin saturation may also be checked to confirm the diagnosis and rule out other causes of fatigue, such as thyroid problems or vitamin B12 deficiency.
How to Treat Iron Deficiency Safely
- Increase heme and non-heme iron intake through food first
- Pair plant-based iron with vitamin C rich foods
- Avoid tea, coffee and calcium supplements within an hour of iron-rich meals
- Only take iron supplements if a blood test confirms deficiency and a doctor recommends it, since excess iron can be harmful
- Address the underlying cause, such as heavy periods or gut absorption issues, alongside dietary changes
When to See a Doctor
Book an appointment with your GP if you notice ongoing fatigue, breathlessness, unusual paleness, or cravings for non-food items such as ice or chalk. These symptoms are straightforward to test for with a simple blood test, and early treatment prevents progression to anaemia.
What Are the First Signs of Low Iron?
The first signs of low iron are usually persistent tiredness that does not improve with rest, mild breathlessness during normal activity, pale skin, and difficulty concentrating. These early symptoms appear before haemoglobin drops, which is why a ferritin blood test is the most reliable way to catch iron deficiency early.
Frequently Asked Questions
Can low iron cause anxiety?
Yes. Low iron affects oxygen delivery to the brain and neurotransmitter function, which can produce symptoms that closely resemble anxiety, including a racing heart, restlessness and difficulty concentrating. A blood test can help distinguish between the two.
How long does it take to fix iron deficiency?
With dietary changes alone, mild deficiency can improve within eight to twelve weeks. With supplements prescribed by a doctor, ferritin levels typically start rising within four to six weeks, though full recovery of iron stores can take three to six months.
What foods should I avoid if I have low iron?
You do not need to avoid specific foods entirely, but tea, coffee, and calcium-rich foods can reduce iron absorption when eaten at the same time as iron-rich meals. Spacing them out by an hour improves absorption.
Can iron deficiency happen without anaemia?
Yes. Iron stores can be depleted, causing fatigue and other symptoms, before haemoglobin actually drops. This stage is often missed because standard blood tests do not always include a ferritin check.
Who is most at risk of iron deficiency?
Women with heavy periods, pregnant women, vegetarians and vegans, endurance athletes, and people with gut conditions such as coeliac disease or inflammatory bowel disease are at the highest risk.
This article is for general information only and is not a substitute for professional medical advice. If you suspect you have iron deficiency, speak to your GP or a qualified healthcare provider before starting any supplement.
About the Author: Written by the Well Ideas editorial team, dedicated to researching and sharing practical, evidence-informed wellness guidance for a healthier everyday life.
