Last updated: October 2026
An overactive thyroid (hyperthyroidism) is when your thyroid makes too much hormone, so your body speeds up. Common symptoms are anxiety and nervousness, a fast or irregular heartbeat, weight loss, feeling hot, shaky hands, poor sleep and loose stools. Graves’ disease is the commonest cause. A blood test diagnoses it and it is usually treatable, so see a GP.
Below: the full symptom list, signs in women, men and older adults, causes, tests, NHS treatment, and when to get urgent help.
Key point: many overactive thyroid symptoms, like a racing heart, anxiety and poor sleep, overlap with stress and anxiety. If you have several of them, or they’re new and not going away, ask your GP for a thyroid blood test rather than guessing.
What is an overactive thyroid?
Your thyroid is a small, butterfly-shaped gland at the front of your neck. Its hormones, thyroxine (T4) and triiodothyronine (T3), affect your heart rate, body temperature, weight and energy. With an overactive thyroid, also called hyperthyroidism or thyrotoxicosis, it makes too much of them and many body processes speed up.
The NHS says it’s about 10 times more common in women than men and typically starts between 20 and 40, though it can happen at any age.
Overactive thyroid symptoms
You’re unlikely to have all of these. These are the symptoms and signs listed by the NHS and the British Thyroid Foundation (BTF):
| Area | What you might notice |
|---|---|
| Heart | A fast or irregular heartbeat (palpitations). See heart palpitations at night |
| Mood | Nervousness, anxiety, irritability, mood swings, feeling restless or hyperactive. See anxiety symptoms |
| Sleep and energy | Difficulty sleeping, feeling tired all the time, muscle weakness |
| Temperature | Sensitivity to heat, warm skin, sweating a lot |
| Weight and appetite | Weight loss, often despite eating more (a few people gain weight) |
| Muscles | Twitching or trembling, shaky hands. See shaky hands |
| Digestion and bladder | Diarrhoea or looser stools, needing to pee more often, persistent thirst |
| Skin, hair and nails | Itchiness, hives, red palms, loose nails, patchy hair loss or thinning |
| Neck | A swelling in the neck from an enlarged thyroid (goitre) |
| Eyes | Red, dry, gritty or watering eyes, sensitivity to light, double vision or bulging eyes (thyroid eye disease) |
| Periods, sex and fertility | Lighter or irregular periods, difficulty getting pregnant, loss of interest in sex |
The NHS says thyroid eye disease affects around 1 in 4 people with Graves’ disease, and mild eye symptoms often improve with treatment. See dry eyes for other causes of gritty eyes.
Overactive thyroid symptoms in women and men
The main symptoms are the same for everyone, but a few differ.
In women
- Periods and fertility: the BTF says untreated Graves’ disease can cause lighter, irregular periods and make it harder to conceive.
- Menopause overlap: NICE warns that thyroid symptoms in menopausal women can be mistaken for menopause. Feeling hot, sweating, poor sleep and mood swings can be either. See hot flushes and night sweats.
- After a baby: temporary postpartum thyroiditis usually shows up in the first six months after birth.
In men
- Sex drive and fertility: the NHS lists loss of interest in sex, and the BTF says sperm count can drop, usually recovering with treatment.
- Heart rhythm: a UK study of 3,049 people with hyperthyroidism found being male, being older and having nodules were each linked to a higher risk of atrial fibrillation, an irregular heart rhythm.
- Easy to miss: because it’s far rarer in men, weight loss, irritability and poor sleep often get put down to stress. See why am I so irritable?
Symptoms in older adults and children
In older people the classic signs are often missing. The same UK study found most classic symptoms were less common in people over 60, apart from weight loss and shortness of breath, and suggested a lower threshold for testing, especially with atrial fibrillation. NICE recommends a thyroid test for anyone with new atrial fibrillation. The NHS adds that an overactive thyroid raises the risk of osteoporosis and heart failure.
Children can have it too. NICE suggests testing children with unusual growth or an unexplained change in behaviour or school performance. If you’re worried about a child, speak to your GP.
Can overactive thyroid symptoms come and go?
Sometimes. The BTF says symptoms can be subtle for a long time, or come on suddenly over days or weeks. Patterns that feel like symptoms coming and going:
- Thyroiditis often starts with an overactive phase, then may swing to an underactive phase before settling.
- Graves’ disease can go into remission and come back. The BTF says relapse risk rises in the year after giving birth.
- Treatment changes: missed tablets, or a dose that isn’t right yet, can bring symptoms back.
How long do symptoms last? The NHS says it may be a few months after starting medicine before you notice the benefit. Eye problems may need separate treatment.
What causes an overactive thyroid?
- Graves’ disease: about 4 in 5 cases, says the NHS. Antibodies push the thyroid to make too much hormone. It runs in families, mostly affects young and middle-aged women, and smoking raises the risk.
- Thyroid nodules: lumps that make extra hormone (a toxic nodule or toxic multinodular goitre), usually in people over 60.
- Thyroiditis: inflammation of the thyroid, including viral and postpartum thyroiditis. The inflamed gland can release extra hormone, and this type is often temporary.
- Too much levothyroxine when treating an underactive thyroid.
- Iodine and some medicines, such as amiodarone, a heart rhythm drug. The NHS says this usually improves once the medicine is stopped, though it can take months. Never stop a prescribed medicine without speaking to your doctor.
- Rarer causes: high hCG in early or multiple pregnancy, a benign pituitary tumour or, rarely, thyroid cancer.
Overactive vs underactive thyroid
The two are easy to mix up by name, but they’re largely opposites. Our guide to underactive thyroid symptoms covers the other side in detail.
| Overactive (hyperthyroidism) | Underactive (hypothyroidism) | |
|---|---|---|
| Heart | Fast or irregular | Slower |
| Weight | Usually weight loss | Weight gain |
| Temperature | Feel hot, sweaty | Feel cold |
| Mood | Anxious, irritable, restless | Low mood, slowed down |
| Bowels | Looser, more frequent | Constipation |
| Periods | Lighter or irregular | Heavier or irregular |
| Energy | Tired but wired | Exhausted, sluggish |
| Blood test | Low TSH, high T4 and/or T3 | High TSH, low T4 |
| Commonest cause | Graves’ disease | Hashimoto’s disease |
Some people move from one to the other: thyroiditis can swing from overactive to underactive, and radioactive iodine or surgery often leads to an underactive thyroid. If “tired but wired” sounds familiar, see tired but wired.
How an overactive thyroid is diagnosed
Your GP will ask about your symptoms and arrange a thyroid function blood test. NICE guideline NG145 suggests starting with TSH (thyroid-stimulating hormone) and, if it’s low, measuring free T4 and free T3 in the same sample.
- Low TSH with high T4 and/or T3 usually means an overactive thyroid.
- TSH receptor antibodies (TRAb) confirm Graves’ disease and help tell it apart from temporary thyroiditis.
- A thyroid scan may follow if antibodies are negative.
Tell whoever takes your blood about any supplements: the BTF says high-dose biotin, common in hair and nail products, can make results wrongly suggest an overactive thyroid.
Overactive thyroid treatment
Most people see a hormone specialist (endocrinologist). The right treatment depends on the cause, how severe it is and any pregnancy plans.
Antithyroid medicines
Carbimazole is usually first, with propylthiouracil (PTU) for people who get side effects, are pregnant or are trying to conceive. For Graves’ disease, NICE recommends a 12 to 18 month course. Some people need medicine for longer, or for life.
Important safety warning: antithyroid medicines can very rarely lower your white blood cells. The NHS says to stop carbimazole and call your doctor or 111 straight away if you get a high temperature, sore throat, mouth ulcers, severe tiredness or flu-like symptoms, so you can have an urgent blood test. Also call straight away if your skin or the whites of your eyes turn yellow, or you get sudden severe stomach pain. Carbimazole can harm an unborn baby, so the MHRA advises women who could get pregnant to use effective contraception while taking it.
Beta blockers
These ease a racing heart, tremor and anxiety while other treatment starts to work. For temporary thyroiditis they’re often all that’s needed.
Radioactive iodine
You swallow a drink or capsule with a low dose of radiation, which destroys some thyroid cells so the gland makes less hormone. NICE recommends it as the first-line definitive treatment for many adults with Graves’ disease. It isn’t suitable in pregnancy, when breastfeeding or with active thyroid eye disease. Afterwards you avoid prolonged close contact with children and pregnant women for about 3 weeks, women avoid pregnancy for at least 6 months, and men should not father a child for at least 4 months.
Surgery
Removing all or part of the thyroid may be advised for a large goitre, severe eye problems, or if other treatments haven’t worked. Without a thyroid you’ll take levothyroxine for life.
Can an overactive thyroid correct itself?
Sometimes, depending on the cause. The BTF says an overactive thyroid caused by thyroiditis is temporary and settles without specific treatment: with viral thyroiditis most people recover completely in two to five months, and most women with postpartum thyroiditis recover fully.
Graves’ disease and toxic nodules don’t usually settle by themselves and need treatment. Even after a course of antithyroid tablets, the BTF puts the chance of a cure at about 30 to 50%. Blood and antibody tests show which type you have.
Living with an overactive thyroid
- Take your tablets every day, and don’t stop them without speaking to your doctor.
- Cut back on caffeine. The NHS lists caffeine, alcohol and nicotine as common palpitation triggers. See does caffeine cause anxiety?
- Stop smoking. The BTF says smoking lowers the chance of a cure with tablets and raises the risk of thyroid eye disease.
- Protect your sleep. It often improves as hormone levels settle. See insomnia and why can’t I sleep?
- Ask before hard exercise if your heart rate has been high.
- Look after your bones with enough calcium and vitamin D and weight-bearing activity.
- Watch your weight after treatment: the BTF notes you may need to eat less once your metabolism returns to normal.
Supplements to avoid
The BTF says no foods or supplements can treat a thyroid disorder, and some can make things worse:
- Iodine, kelp and sea moss: extra iodine is unnecessary when you’re being treated for an overactive thyroid and can work against your medicine. See sea moss.
- Ashwagandha: it can affect thyroid hormone levels, and there are case reports of an overactive thyroid in people taking it. Anyone with a thyroid condition should avoid ashwagandha and products containing it. See ashwagandha side effects and our UK ashwagandha safety review.
- High-dose biotin: can upset thyroid test results.
Check any supplement with your GP or pharmacist first, especially while you’re on thyroid medicine.
If you’d like a caffeine-free drink as part of your evening routine, our Magnesium Glycinate Sleep Complex is a magnesium and herbal drink with no ashwagandha and no added iodine. Magnesium contributes to normal psychological function and to a reduction of tiredness and fatigue. It doesn’t treat thyroid conditions, so check with your pharmacist or specialist before taking it alongside thyroid medicine. It’s for adults only, and we don’t recommend our products during pregnancy or breastfeeding.
Pregnancy and fertility
If you’re pregnant or planning a pregnancy, speak to your GP or specialist early. Poorly controlled hyperthyroidism raises the risk of pre-eclampsia, miscarriage and premature birth, and your medicine may need changing. Don’t stop antithyroid tablets yourself: the BTF says an untreated overactive thyroid is a greater risk to a pregnancy than the medicine. The NHS and BTF pregnancy guide have more detail.
When to see a GP or get urgent help
See a GP if you have symptoms such as unexplained weight loss, a racing heart, feeling shaky, anxious or hot, or a swelling in your neck. A written list of your symptoms helps.
Call 999 if someone has a very fast heartbeat with a high temperature, severe agitation or confusion, yellowing skin or eyes, or loses consciousness. The NHS says this can be a thyroid storm, a rare but life-threatening flare-up that infection, pregnancy or not taking medicine properly can trigger. Also call 999 or go to A&E for palpitations that don’t go away, or with chest pain, shortness of breath or feeling faint.
On carbimazole or PTU with a sore throat, fever or mouth ulcers? Stop the tablets and contact your doctor or 111 straight away for a blood test.
A racing heart with a sense of dread can also be panic: see panic attack symptoms and what to do.
See also other common causes of palpitations.
FAQs
How do you know if you have an overactive thyroid?
Common signs are a fast or irregular heartbeat, weight loss, feeling hot and sweaty, shaky hands, anxiety and poor sleep. Only a blood test can confirm it, so see your GP if you have several of these symptoms.
What are the first signs of an overactive thyroid in women?
Often anxiety or irritability, a racing heart, feeling hot, poor sleep and weight loss despite eating normally. Periods may become lighter or irregular. These can be mistaken for stress or menopause.
What are overactive thyroid symptoms in men?
Men get the same main symptoms as women, plus a possible loss of interest in sex and a lower sperm count. Men with hyperthyroidism also have a higher risk of atrial fibrillation.
Can an overactive thyroid correct itself?
When it’s caused by thyroiditis, it usually settles within a few months without specific treatment. Graves’ disease and toxic nodules usually need treatment.
Can overactive thyroid symptoms come and go?
Yes. Thyroiditis can cause an overactive phase that later settles, and Graves’ disease can go into remission and come back. Missed tablets can also bring symptoms back.
Can an overactive thyroid cause anxiety?
Yes. Nervousness, anxiety, irritability and mood swings are common symptoms, and they usually improve as the thyroid is treated. NICE suggests considering a thyroid test for unexplained anxiety.
Should I avoid ashwagandha with a thyroid condition?
Yes. Ashwagandha can affect thyroid hormone levels, so anyone with a thyroid condition should avoid it and products containing it. Check any supplement with your GP or pharmacist.
Sources
- NHS. Overactive thyroid (hyperthyroidism), including symptoms, causes, diagnosis, treatment and complications.
- NHS. Carbimazole.
- NICE. Thyroid disease: assessment and management (NG145).
- British Thyroid Foundation. Hyperthyroidism, Thyroiditis and Diets and supplements for thyroid disorders.
- MHRA. Carbimazole: increased risk of congenital malformations; strengthened advice on contraception. Drug Safety Update, February 2019.
- Boelaert K, et al. Older subjects with hyperthyroidism present with a paucity of symptoms and signs: a large cross-sectional study. J Clin Endocrinol Metab, 2010. PMID 20392869.
- Kamal HI, et al. Ashwagandha as a unique cause of thyrotoxicosis presenting with supraventricular tachycardia. Cureus, 2022. PMID 35475098.
- NCCIH. Ashwagandha.
This guide is general information, not medical advice. Always follow the advice of your GP or specialist. Evopure makes the Magnesium Glycinate Sleep Complex.
