--- title: "Overactive thyroid (hyperthyroidism): Symptoms & Treatment" description: "A plain-English guide to an overactive thyroid — symptoms, causes, diagnosis and treatment in the UK." url: https://healthanswers.co.uk/conditions/overactive-thyroid/ robots: noindex --- # Overactive thyroid (hyperthyroidism): Symptoms & Treatment Health A–Z A plain-English guide to an overactive thyroid — symptoms, causes, diagnosis and treatment in the UK. Written by HealthAnswers editorial team Medically reviewed by [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) Reviewed 3 July 2026 ## Quick answer What is overactive thyroid? An overactive thyroid (hyperthyroidism) means the thyroid gland produces too much thyroid hormone, speeding up the body's metabolism. Symptoms include weight loss despite eating normally, rapid heartbeat, anxiety, tremor and heat intolerance. Treatment options include antithyroid medicines, radioactive iodine or surgery — a GP arranges blood tests to confirm diagnosis. ## Who is this page for? This page is for people in the UK who want a plain-English overview of Overactive thyroid (hyperthyroidism), including when to seek help and what NHS care usually involves. It explains general information, not what is wrong with you personally. ## Who should skip this page? Skip this page if you need a diagnosis, a prescription, or emergency care. It cannot replace a GP, pharmacist, NHS 111 or 999. If you are in immediate danger, call 999; for urgent advice that is not life-threatening, call 111 in England, Scotland or Wales, or use your GP out-of-hours service in Northern Ireland. On this page 9 sections ## Key facts about overactive thyroid - Opposite of underactive thyroid — too much hormone rather than too little. - Common causes include Graves' disease, thyroid nodules, and thyroiditis. - Symptoms include racing heart, weight loss, anxiety and feeling hot. - Diagnosed with a blood test — TSH low, free T4 and/or T3 high. - Effective treatments exist — most people manage well long-term. ## What is an overactive thyroid? Hyperthyroidism means your **thyroid gland** — a small butterfly-shaped gland in the neck — produces **too much thyroid hormone**. These hormones control metabolism: how fast your body uses energy. Excess hormone speeds everything up, affecting heart rate, weight, mood, digestion and more. It is the opposite of **underactive thyroid (hypothyroidism)**, where too little hormone is produced. ## Symptoms Hyperthyroidism symptoms develop gradually and may be mistaken for stress or anxiety: - Weight loss despite normal or increased appetite - Rapid or irregular heartbeat — palpitations - Anxiety, irritability and restlessness - Tremor — shaky hands - Heat intolerance — feeling hot when others are comfortable - Excessive sweating - **Diarrhoea or frequent bowel movements - Fatigue and muscle weakness - Difficulty sleeping - Lighter or absent periods in women - Swelling at the base of the neck (goitre) — visible or palpable Older adults may have fewer obvious symptoms — apathy and heart failure can dominate. ## Common causes **Graves’ disease** — the most common cause in the UK. An autoimmune condition where the immune system stimulates the thyroid to overproduce hormone. Can affect the eyes (thyroid eye disease). **Toxic nodular goitre** — one or more nodules in the thyroid produce excess hormone independently. **Thyroiditis** — temporary overactivity as the gland becomes inflamed — often followed by a period of underactivity. Subacute thyroiditis may follow a viral illness. **Medication** — too much levothyroxine for an underactive thyroid, or iodine-containing medicines. ## Diagnosis A GP diagnoses hyperthyroidism with **blood tests**: - TSH (thyroid stimulating hormone) — usually low or undetectable - Free T4 and free T3 — elevated Further tests identify the cause — thyroid antibodies (Graves’ disease), ultrasound scan, or radioactive iodine uptake scan. ## Treatment options **Antithyroid medicines** — carbimazole (or propylthiouracil in pregnancy) blocks hormone production. Usually taken for 12 to 18 months. Can induce long-term remission in Graves’ disease. **Radioactive iodine** — taken as a drink or capsule. The iodine is absorbed by the thyroid and destroys overactive cells. Often causes permanent hypothyroidism requiring lifelong levothyroxine — which is easier to manage than overactivity. **Surgery (thyroidectomy)** — removes part or all of the thyroid. Used when other treatments unsuitable, large goitre, or suspected cancer. **Beta-blockers** — propranolol controls rapid heartbeat and tremor while waiting for definitive treatment to work. ## Hyperthyroidism and pregnancy Untreated hyperthyroidism in pregnancy risks miscarriage, prematurity, and low birth weight. Treatment is adjusted for pregnancy — specialist endocrine care is needed. If planning pregnancy, discuss treatment with a GP first. ## Thyroid eye disease Graves’ disease can cause **thyroid eye disease** — bulging eyes, dryness, grittiness, double vision, and in severe cases vision loss. Requires specialist ophthalmology care alongside thyroid treatment. ## Living with hyperthyroidism Most people respond well to treatment. After radioactive iodine or surgery, you may develop **hypothyroidism** — managed with daily levothyroxine tablets and regular blood test monitoring. Avoid excess **iodine** (some supplements and seaweed) which can worsen overactivity. ## When to see a GP See a GP for unexplained weight loss, persistent palpitations, tremor, or other symptoms above. Hyperthyroidism is treatable — early diagnosis prevents complications including heart rhythm problems and osteoporosis. Seek **urgent help** for severe chest pain, breathlessness at rest, confusion, or very high fever with agitation — possible **thyroid storm**, a rare life-threatening flare. ## ! When to see a GP about overactive thyroid See a GP if you have unexplained weight loss, persistent rapid heartbeat, tremor, heat intolerance, or eye changes. Seek urgent help for severe chest pain, breathlessness at rest, confusion, or very high fever with agitation (thyroid storm — rare emergency). Thyroid problems are diagnosed with blood tests — do not self-diagnose from symptoms alone. ## Common questions about overactive thyroid What are the symptoms of an overactive thyroid? Weight loss despite normal appetite, rapid or irregular heartbeat, anxiety and irritability, trembling hands, heat intolerance and sweating, diarrhoea, fatigue, difficulty sleeping, and in women lighter or absent periods. Some people notice a swelling at the front of the neck (goitre). What causes hyperthyroidism? Graves' disease — an autoimmune condition — is the most common cause in the UK. Other causes include toxic thyroid nodules, thyroiditis (temporary overactivity as the gland inflames), and excess iodine or thyroid hormone medication. How is an overactive thyroid treated? Antithyroid medicines (carbimazole) reduce hormone production. Radioactive iodine shrinks the gland. Surgery removes part or all of the thyroid. Treatment choice depends on cause, age, and whether you are pregnant or planning pregnancy. What is the difference between overactive and underactive thyroid? Overactive (hyperthyroidism) speeds metabolism — weight loss, racing heart, feeling hot. Underactive (hypothyroidism) slows metabolism — weight gain, tiredness, feeling cold. Both are diagnosed with blood tests and need different treatment. Can hyperthyroidism cause eye problems? Yes — Graves' disease can cause thyroid eye disease (bulging eyes, grittiness, double vision). Tell a GP if you have eye symptoms alongside thyroid problems — specialist treatment may be needed. ## Sources - [NHS — Overactive thyroid (hyperthyroidism)](https://www.nhs.uk/conditions/overactive-thyroid-hyperthyroidism/)