Anaemia: Causes, Symptoms & NHS Treatment

Anaemia is a condition in which the blood has fewer red blood cells, or less haemoglobin, than normal. This reduces the blood’s ability to carry oxygen to body tissues, causing fatigue and other symptoms. Anaemia is extremely common — affecting around one billion people worldwide — and has many possible causes. This guide covers the main types of anaemia seen in the UK, how they are diagnosed, and NHS treatment options.

What Is Anaemia?

Haemoglobin is the protein in red blood cells that carries oxygen from the lungs to the rest of the body. Anaemia is defined by the World Health Organization (WHO) as haemoglobin below 130g/L in adult men and below 120g/L in adult non-pregnant women (110g/L in pregnant women). Low haemoglobin results in reduced oxygen delivery to tissues and the characteristic symptoms of fatigue, breathlessness, and pallor.

Anaemia is not a diagnosis in itself — it is a sign of an underlying condition. Identifying and treating the cause is as important as treating the anaemia.

Types and Causes of Anaemia

Iron Deficiency Anaemia (the Most Common Type)

Iron is essential for haemoglobin synthesis. Iron deficiency is the most common cause of anaemia globally and in the UK. Causes include:

• Blood loss — heavy menstrual periods (most common in premenopausal women); gastrointestinal bleeding (ulcers, colorectal cancer, coeliac disease, inflammatory bowel disease, NSAIDs) — always the priority cause to exclude in men and postmenopausal women
• Inadequate dietary intake — vegans and vegetarians are at higher risk; iron from meat (haem iron) is much better absorbed than plant-based iron
• Malabsorption — coeliac disease, Crohn’s disease, and gastric surgery impair iron absorption
• Increased requirements — pregnancy and breastfeeding greatly increase iron needs

B12 Deficiency Anaemia

Vitamin B12 is required for DNA synthesis in red blood cells and for myelin production in nerves. Deficiency causes macrocytic anaemia (large red blood cells) and, if severe, neurological damage. Causes include:

• Pernicious anaemia — an autoimmune condition causing lack of intrinsic factor, which is essential for B12 absorption in the terminal ileum; the most common cause in the UK; requires lifelong B12 injections
• Dietary deficiency — strict vegans are at risk as B12 is only found in animal products
• Malabsorption — terminal ileum disease or resection (Crohn’s disease), gastric surgery
• Medications — metformin reduces B12 absorption; proton pump inhibitors may reduce absorption over time

Folate Deficiency Anaemia

Folate (folic acid) is also required for red blood cell DNA synthesis and causes macrocytic anaemia. Causes include:

• Poor diet — folate is found in green leafy vegetables; UK diet is often low in folate
• Alcohol excess — impairs folate absorption and increases excretion
• Malabsorption — coeliac disease and inflammatory bowel disease
• Increased requirements — pregnancy; haemolytic anaemias
• Medications — methotrexate, phenytoin, and trimethoprim interfere with folate metabolism

Anaemia of Chronic Disease (ACD)

ACD is the second most common cause of anaemia after iron deficiency. It occurs in the context of chronic inflammatory, infectious, or malignant conditions (rheumatoid arthritis, CKD, cancer, chronic infection). Inflammation diverts iron from circulation and suppresses erythropoietin production. ACD causes normochromic normocytic anaemia. Treatment focuses on the underlying condition.

Haemolytic Anaemia

Premature destruction of red blood cells (haemolysis) causes anaemia. Causes include autoimmune haemolytic anaemia (warm or cold antibody type), hereditary conditions (sickle cell disease, thalassaemia, hereditary spherocytosis, G6PD deficiency), and drug-induced haemolysis.

Aplastic Anaemia

Failure of the bone marrow to produce blood cells; causes pancytopenia (anaemia, thrombocytopenia, neutropenia). Can be idiopathic, autoimmune, drug-induced (chloramphenicol, some NSAIDs), or related to viral infection. Requires specialist haematology management.

Symptoms of Anaemia

Symptoms depend on the severity and speed of onset. Common symptoms include:

• Fatigue and weakness — the most common symptom; often profound
• Breathlessness on exertion
• Palpitations — the heart works harder to compensate
• Pallor — pale skin, pale inner eyelids (conjunctival pallor), pale nail beds
• Headache and difficulty concentrating
• Dizziness
• Angina — in people with underlying coronary artery disease

Additional symptoms specific to iron deficiency: brittle nails, hair loss, koilonychia (spoon-shaped nails), pica (craving non-food substances such as ice or clay), glossitis (smooth, sore tongue), angular stomatitis.

B12/folate deficiency specific: peripheral neuropathy (tingling, numbness in hands and feet), subacute combined degeneration of the spinal cord (B12 deficiency — progressive weakness, ataxia), glossitis, cognitive impairment.

NHS Diagnosis

Initial investigation is a full blood count (FBC) with red cell indices:

• MCV (mean corpuscular volume) — small cells (microcytic, MCV below 80fL) suggest iron deficiency, thalassaemia, or sideroblastic anaemia; large cells (macrocytic, MCV above 100fL) suggest B12/folate deficiency or hypothyroidism; normal-sized cells (normocytic) suggest anaemia of chronic disease, haemolysis, or acute blood loss
• Ferritin — low in iron deficiency; the single most useful test for iron stores. However, ferritin is an acute-phase reactant and may be falsely normal in iron deficiency with coexisting inflammation
• Serum iron, TIBC, transferrin saturation — low iron and low transferrin saturation, high TIBC in iron deficiency
• Serum B12 and folate
• Reticulocyte count — raised in haemolytic anaemia and in response to treatment; low in aplastic anaemia
• Blood film — morphology helps identify the type: hypochromic microcytes (iron deficiency), megaloblasts (B12/folate), spherocytes (hereditary spherocytosis or AIHA), sickle cells
• Thyroid function — hypothyroidism causes normocytic or macrocytic anaemia
• Coeliac serology — anti-tTG IgA in unexplained iron deficiency

Endoscopy (gastroscopy and/or colonoscopy) is essential in men and postmenopausal women with iron deficiency anaemia to exclude gastrointestinal malignancy and upper GI pathology. NICE NG12 recommends urgent referral (2-week wait) for colorectal cancer investigation in patients with unexplained iron deficiency anaemia.

NHS Treatment

Iron Deficiency Anaemia

Oral ferrous sulphate (200mg, containing 65mg elemental iron, once to three times daily) is first-line. Take on an empty stomach for best absorption; vitamin C (orange juice) enhances non-haem iron absorption. Common side effects: constipation, nausea, black stools. Taking every other day (alternate days) has been shown to improve absorption due to hepcidin regulation, with fewer side effects — increasingly recommended in NICE guidance.

Alternative oral preparations: ferrous fumarate, ferrous gluconate (better tolerated but lower elemental iron content). Liquid iron preparations for children and those unable to swallow tablets.

IV iron (e.g., ferric carboxymaltose — Ferinject; or iron sucrose) is used when oral iron is not tolerated, is malabsorbed (coeliac disease, IBD, post-bariatric surgery), or when rapid repletion is needed (severe anaemia, pregnancy). Given as a single outpatient infusion.

Haemoglobin should rise by approximately 10-20g/L over 3-4 weeks with treatment. Continue iron for at least 3-6 months after haemoglobin normalises to replenish stores. Treat the underlying cause to prevent recurrence.

Vitamin B12 Deficiency

Hydroxocobalamin injections are given as 1mg IM three times per week for 2 weeks (loading), then every 3 months for life for pernicious anaemia or other causes of malabsorption. Oral B12 supplementation (1000 micrograms daily) is effective for dietary deficiency in vegans. Neurological symptoms require earlier and more aggressive treatment — injections every 2 months for life where neurological involvement is present.

Folate Deficiency

Folic acid 5mg daily orally for 4 months. Identify and treat the underlying cause. Important: ensure B12 deficiency is excluded before treating with folate alone — treating folate deficiency with folic acid in the presence of unrecognised B12 deficiency can worsen neurological damage.

Living Well with Anaemia

• Iron-rich foods: red meat, liver, dark leafy vegetables (spinach, kale), lentils, beans, fortified cereals, tofu, pumpkin seeds
• Improve iron absorption: eat vitamin C-rich foods (citrus, peppers) with iron-rich meals; avoid tea and coffee with iron-rich meals (tannins inhibit iron absorption)
• B12-rich foods: meat, fish, eggs, dairy, fortified plant milks and nutritional yeast (for vegans)
• Folate-rich foods: green leafy vegetables, broccoli, peas, chickpeas, oranges, fortified breakfast cereals
• Take supplements as prescribed — complete the full course even if you feel better
• Report persistent symptoms — if fatigue persists despite treatment, reassess for the underlying cause