Hypothermia

A core temperature below 35C. In an older person it develops indoors, over days, without anybody noticing them shivering.

What it is

A dangerous drop in core body temperature below 35 degrees Celsius.

The dramatic version, from cold water or exposure, is not the common one in the UK. The common one is an older or frail person becoming cold indoors, over hours or days, in an under-heated home. That version is quiet: no dramatic shivering, because the shivering response fails as it worsens and is already blunted by age.

Risk is raised by age, malnutrition, hypothyroidism, dementia, stroke, immobility, alcohol, and by many medicines including sedatives, antipsychotics and some antidepressants.

Alcohol is specifically dangerous because it opens the skin's blood vessels, so the person feels warm while losing heat faster.

A person who has fallen and lain on a floor, even indoors, is at high risk, and hypothermia and the fall each make the other worse.

Excess winter deaths in the UK are substantially about cold homes, and fuel poverty is therefore a clinical issue, not only a social one. Asking whether somebody can afford to heat their home is a legitimate health question.

Signs you might notice

Early: shivering, cold pale skin, tiredness, fast breathing.

As it worsens: shivering stops, which is a bad sign rather than a good one; confusion, slurred speech, drowsiness, clumsiness and stumbling; slow, shallow breathing; a slow, weak pulse.

In a baby: cold to touch, unusually quiet and still, floppy, refusing to feed, and skin that looks red and healthy, which is misleading.

999 for anybody with confusion, drowsiness, or who has stopped shivering.

Do not assume somebody is simply confused or drunk. Take the temperature. A low reading on an ordinary thermometer in a cold, confused person is the diagnosis.

How it can affect day-to-day life

The indoor version is the one that gets missed in care at home. Somebody sitting in a cold room with a blanket, eating little, moving less, is not obviously an emergency until they are confused.

Being cold is normalised, particularly among older people who grew up without central heating and who ration the heating out of anxiety about bills.

Room thermometers are cheap and make an invisible problem visible. Around 18C is the recommended minimum for a living space.

Practical support is available and under-claimed: Winter Fuel Payment, Cold Weather or Warm Home Discount schemes, Pension Credit which unlocks others, and priority services registers with energy suppliers.

For anybody who has been on the floor after a fall, hypothermia should be assumed and checked rather than waited for.

Supporting someone well

Take the temperature rather than judging by appearance. Take it seriously below 35C.

Call 999 for confusion, drowsiness or a person who has stopped shivering.

While waiting: move somewhere warm, remove wet clothing, wrap in dry blankets including the head, and give warm sweet drinks only if fully alert.

Do not give alcohol, do not rub the limbs, and do not use direct heat such as a hot bath, hot water bottle or fire, all of which can be dangerous.

Handle gently; rough movement in severe hypothermia can trigger a dangerous heart rhythm.

Put a thermometer in the living room and aim for at least 18C.

Ask about money: fuel payments, Pension Credit, and the supplier's priority services register.

Check on older neighbours in cold weather, and check the heating actually works before winter rather than during it.

Where to get help

999 for moderate or severe hypothermia.

A GP practice or NHS 111 for someone who is cold and unwell but alert.

Age UK advice line on 0800 678 1602 for winter warmth and benefits.

Citizens Advice for fuel debt and energy support.