Health condition · Clinically reviewed
Hashimoto’s thyroiditis, the autoimmune cause of most hypothyroidism.
Autoimmune destruction of the thyroid — the most common cause of hypothyroidism in the UK. TPO antibodies confirm it; levothyroxine remains the mainstay of treatment.
Why trust this guide
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Clinically reviewed
Written by our editorial team and reviewed by a registered UK clinician before publication.
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Sourced from guidance
Every claim is checked against NICE, BTA or peer-reviewed sources you can see at the end.
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Current for 2026
Reflects UK guidance on antibody testing, levothyroxine dosing and coexisting autoimmune care.
Key facts
Hashimoto’s thyroiditis at a glance.
The essentials, in plain English — what it is, how common it is, the antibody signature, and how it is treated in the UK today.
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What it is
Autoimmune chronic lymphocytic thyroiditis — the immune system slowly destroys thyroid tissue.
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How common
The most common cause of hypothyroidism in the UK.
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Antibody signature
Anti-TPO antibodies are positive in more than 95% of cases; anti-Tg antibodies often too.
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Who gets it
Higher risk in women and in those with a family history of autoimmune disease.
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Coexisting disease
Frequently coexists with vitiligo, coeliac disease, type 1 diabetes and pernicious anaemia.
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Treatment
Levothyroxine, dose-adjusted to TSH — the same replacement therapy used for any primary hypothyroidism.
Why this guide matters
An antibody, a tablet, and the rest of your life feeling normal.
Hashimoto’s is common, easy to confirm and highly treatable — once the right questions are asked. The three points below shape the rest of this guide.
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Antibodies confirm the cause
Anti-TPO positivity settles whether hypothyroidism is autoimmune.
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Levothyroxine still does the work
Right target TSH, taken correctly, transforms symptoms.
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Watch what travels with it
Coeliac, B12 deficiency and other autoimmune conditions cluster with Hashimoto’s.
How the diagnosis is made
From first blood test to a settled dose.
The steps a UK GP will normally follow, in order — so you know what to expect and why.
Phase 1 · Recognising
First blood tests and antibody panel
Phase 2 · Confirming
Ultrasound and autoimmune screening
Phase 3 · Managing
Structured levothyroxine titration
- 01
Recognising
TSH and free T4
The first blood tests — raised TSH with low free T4 confirms overt hypothyroidism from Hashimoto’s.
- 02
Recognising
Anti-TPO antibodies
Positive in more than 95% of cases; anti-thyroglobulin (anti-Tg) antibodies are checked alongside.
- 03
Recognising
Thyroid ultrasound
Requested if there is a goitre, a palpable nodule or diagnostic uncertainty.
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Confirming
Screen coexisting autoimmune
Coeliac serology and vitamin B12 — Hashimoto’s clusters with other autoimmune conditions.
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Confirming
Baseline lipids and FBC
Untreated hypothyroidism raises cholesterol and can cause a normocytic anaemia — worth a baseline.
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Confirming
Endocrinology referral
For unusual features — large or rapidly growing goitre, suspicious nodule, pregnancy or refractory symptoms.
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Managing
Structured levothyroxine titration
Weight-based starting dose, retest TSH at 6-8 weeks, adjust in 25 mcg steps until stable.
Typical timeline: 6-12 weeks from first blood test to a settled dose.
Symptoms
What Hashimoto’s hypothyroidism actually feels like.
Symptoms come on slowly and overlap with other common conditions — which is why Hashimoto’s is often missed for months or years before antibodies are checked.
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Fatigue
Persistent tiredness that rest does not fix — often the earliest symptom.
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Weight gain
Slow, gradual gain as metabolism slows.
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Cold intolerance
Feeling cold when others are comfortable.
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Goitre
A firm, sometimes tender, diffusely enlarged thyroid — the immune infiltrate itself.
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Depression
Low mood and slowed thinking — often improve once TSH is normalised.
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Constipation
Slow bowels as gut transit falls.
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Hair changes
Coarse, dry hair, thinning of the outer eyebrows and dry skin.
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Red flag — myxoedema coma
Very rare but life-threatening — profound hypothyroidism with confusion or hypothermia. Call 999.
Treatment
How Hashimoto’s thyroiditis is treated in the UK.
Levothyroxine, taken correctly, still does most of the work. Here is what each part of the plan does — and why the details matter.
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Levothyroxine
Synthetic T4 — the mainstay. Weight-based starting dose (typically 1.6 mcg/kg/day in adults; lower in older adults or cardiac disease).
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TSH-guided titration
Recheck TSH at 6-8 weeks, adjust in 25 mcg increments until TSH sits in the target range for your age.
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Combination T4/T3
Considered in specialist care for refractory symptoms despite biochemical control — not first line.
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Selenium
Limited evidence for reducing antibody titres; not recommended routinely by UK guidance.
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Pregnancy dose optimisation
Levothyroxine requirement rises by ~25-30% early in pregnancy; TSH targets are tighter — plan ahead of conception.
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Ultrasound surveillance
For any coexisting nodule — periodic ultrasound to monitor size and appearance.
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Autoimmune screen and monitor
Baseline check for coeliac, B12 and vitamin D — repeated if new symptoms emerge.
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Coexisting autoimmune management
Vitiligo, coeliac disease, type 1 diabetes and pernicious anaemia all need their own treatment pathways.
What this guide is based on
The sources behind every number on this page.
UK national guidance and specialist society standards, current at the time of last review.
Key references
Guidelines and standards we relied on.
A quiet reminder
This guide is for information, not medical advice.
Your GP knows your history and can tell you which parts apply to you. If in doubt, ask for a thyroid function test and TPO antibodies.
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British Thyroid Association. Guidelines on the management of primary hypothyroidism.
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NICE. Thyroid disease: assessment and management (NG145).
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European Thyroid Association. Guidelines on autoimmune thyroid disease.
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Thyroid UK. Patient information on Hashimoto’s thyroiditis.
Red flags
When Hashimoto’s needs urgent attention.
Hashimoto’s is usually a slow, steady condition. These are the situations where it stops being routine — and you should act promptly.
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Myxoedema coma
Very rare — profound hypothyroidism with confusion, hypothermia, bradycardia. Call 999.
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Cardiac arrhythmia on over-replacement
New palpitations or atrial fibrillation — recheck TSH and reduce dose.
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Osteoporosis on over-replacement
Chronic suppressed TSH increases fracture risk — aim for TSH in range.
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Suspicious thyroid nodule
Firm, growing or hard nodule on ultrasound — refer for FNA and specialist review.
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Post-partum thyroiditis
A transient thyroiditis in the year after delivery — often missed, worth checking.
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Pregnancy planning
Tight TSH targets are needed before conception — review dose early.
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Coexisting adrenal insufficiency
Rare but important — start hydrocortisone before levothyroxine to avoid crisis.
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Overlap Graves-Hashimoto
Fluctuating thyroid function with both stimulating and blocking antibodies — needs specialist care.
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Levothyroxine allergy
True allergy is rare — trial alternative brands or liquid formulations before combination therapy.
Living with it
A lifelong condition, a very manageable one.
Four small things that make the biggest difference day to day — timing, consistency, life-stage changes and yearly reviews.
A quiet reminder
Consistency beats intensity, every time.
Take it at the same time every day, on an empty stomach — and keep the yearly blood test.
- 01 Timing
Own the routine
Take levothyroxine at the same time daily, on an empty stomach, apart from other tablets.
- 02 Consistency
Stick to one brand where you can
Report symptom change if a switch happens — some people notice a real difference.
- 03 Life stages
Doses change through life
Pregnancy, illness, weight change and new drugs all affect requirement.
- 04 Reviews
Annual TSH once stable
A yearly blood test catches drift early — do not stop taking it because you feel well.
Frequently asked
Everything we get asked about Hashimoto’s.
Quick answers on antibodies, levothyroxine, diet, cancer risk and pregnancy.
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How is Hashimoto’s thyroiditis diagnosed?
By blood tests — raised TSH with low free T4 confirms hypothyroidism, and positive anti-TPO antibodies confirm the autoimmune cause. Ultrasound is added if there is a goitre or nodule.
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Is Hashimoto’s the same as hypothyroidism?
Not quite — Hashimoto’s is the autoimmune cause of hypothyroidism. It is the most common cause in the UK, but hypothyroidism can also follow surgery, radiotherapy or certain medications.
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Do I need treatment if my TSH is normal but antibodies are positive?
Not usually — positive antibodies without abnormal TSH are watched, not treated. It signals a higher chance of progression, so periodic TSH checks are sensible.
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Will diet cure Hashimoto’s?
No diet has been shown to reverse Hashimoto’s. If coeliac disease coexists, a gluten-free diet is essential for that reason. Selenium has limited evidence and is not routinely recommended.
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Can Hashimoto’s cause thyroid cancer?
A small increase in the risk of thyroid lymphoma has been reported, but the absolute risk remains very low. Any growing or suspicious nodule should be assessed with ultrasound.
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What about pregnancy?
Levothyroxine requirement rises by 25-30% early in pregnancy and TSH targets are tighter. Ideally reviewed before conception and monitored closely through each trimester.