Health condition
Myxoedema coma awareness
Myxoedema coma is decompensated severe hypothyroidism - hypothermia, slowed breathing, bradycardia and declining consciousness, usually in older people in winter - a rare but frequently fatal emergency requiring immediate hospital care.
Why trust this guide
- 01
Editorial team
Written by our editorial team from the UK sources listed on each page.
- 02
Sourced from guidance
Checked against current NHS and UK specialist society guidance at the time of review.
- 03
Current for 2026
Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.
Key facts
The essentials at a glance.
The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.
-
Classic setting: an older woman with untreated or abandoned hypothyroidism, tipped over by infection, cold exposure, sedatives or a heart event
-
Key features: low body temperature, slow heart rate, slowed breathing, low sodium, puffy features and progressive drowsiness
-
This is a 999 emergency - mortality is high even with treatment
-
Hospital treatment: intravenous thyroid hormone, hydrocortisone (until coexisting adrenal insufficiency is excluded), passive rewarming and organ support
-
Prevention: never stop levothyroxine without advice, and take non-collection of prescriptions in older relatives seriously
Understanding the condition
What it is and what happens next.
What causes it, how it is diagnosed, and the treatment routes available in the UK.
What it is and how it feels
Untreated hypothyroidism slows everything, and the body can compensate for years - until an infection, a cold snap, an opioid or sedative, or a stroke demands reserves that no longer exist. Metabolism then spirals downward: temperature falls, breathing shallows and retains carbon dioxide, the heart slows, sodium drifts down and the patient becomes progressively unrousable. The name misleads; full coma is late, and any unusual drowsiness in a hypothyroid person is enough to act on.
Diagnosis and treatment routes
Treatment cannot wait for confirmation: intensive-care admission, intravenous levothyroxine (with T3 in some protocols), hydrocortisone until adrenal insufficiency is excluded, gentle rewarming, ventilatory support and treatment of the trigger. The practical message for families is vigilance - lapsed prescriptions, missed appointments and winter withdrawal in an elderly hypothyroid relative are warnings worth acting on, via 999 if drowsiness or hypothermia appear. Routine thyroid care questions can be reviewed privately, typically within about two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a consultant endocrinologist (emergency, hospital-based). Your GP can refer you on the NHS, or you can arrange a private consultation directly.
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, see them - and seek urgent care for any of the emergency symptoms described above.
Frequently asked
Common questions about Myxoedema coma awareness.
Quick, plain-English answers to what people ask us most.
-
What is myxoedema coma?
Myxoedema coma is a rare, severe, life-threatening complication of very poorly controlled or undiagnosed hypothyroidism, causing dangerously low body temperature, confusion or coma, and multiple organ dysfunction.
-
What causes myxoedema coma?
It typically occurs in people with long-standing, severe untreated hypothyroidism, often triggered by an additional stressor such as infection, cold exposure, surgery, or certain sedating medications that tip decompensated thyroid function into crisis.
-
What are the symptoms of myxoedema coma?
Symptoms include profound lethargy progressing to confusion or unconsciousness, very low body temperature, slow heart rate, low blood pressure and slowed breathing, often in someone with pre-existing signs of severe hypothyroidism such as dry skin and swelling.
-
Is myxoedema coma dangerous?
Yes, myxoedema coma is a medical emergency with a high risk of death if not treated urgently in an intensive care setting, given the severe disruption to multiple body systems it causes.
-
How is myxoedema coma treated?
Treatment requires emergency hospital admission, usually to intensive care, with urgent thyroid hormone replacement, supportive care for breathing and circulation, treatment of any underlying trigger such as infection, and careful monitoring.
-
How can myxoedema coma be prevented?
Prevention relies on timely diagnosis and adequate treatment of hypothyroidism, regular monitoring of thyroid function, and prompt medical attention for anyone with known hypothyroidism who becomes unusually unwell, especially during illness or cold weather.
-
When should I seek emergency care for possible myxoedema coma?
This is a medical emergency; anyone with known hypothyroidism who becomes confused, extremely lethargic or unusually cold should receive emergency assessment immediately by calling 999 or attending A&E without delay.