More than four million people in the UK live with diabetes, and most manage it quietly and capably every day. But blood glucose can swing out of range with little warning, and when it does, the people around them — family, friends, colleagues and neighbours — are often the first to notice. A little knowledge goes a surprisingly long way.

Two Very Different Emergencies

Diabetes emergencies fall into two broad camps, and mixing them up is the most common mistake.

Hypoglycaemia (a "hypo") means blood glucose has dropped too low — generally below 4 mmol/L. It comes on over minutes, often triggered by insulin, certain tablets, a missed or delayed meal, unplanned exercise or alcohol. Hyperglycaemia means glucose has climbed too high. It builds over hours or days and can develop into diabetic ketoacidosis. Both can leave someone confused, but a hypo is the more immediately dangerous of the two.

Recognising a Hypo

Early warning signs include:

• Shaking, trembling or a racing heart
• Sweating, a cold clammy feel and pale skin
• Sudden hunger, or tingling lips and tongue
• Irritability, tearfulness or behaviour that seems out of character
• Difficulty concentrating, confusion or slurred speech

Some people — particularly those who have lived with type 1 diabetes for many years — lose these early warnings altogether. In severe cases someone may become drowsy, have a seizure or lose consciousness. Never assume a confused, unwell person is simply drunk or tired. If they have diabetes and something feels off, check their blood glucose if you can.

Treating a Hypo: Sugar First

If the person is conscious and able to swallow, give 15 to 20 grams of fast-acting carbohydrate straight away. Any of these will do:

• Four or five glucose tablets
• A small glass (150–200ml) of fruit juice or full-sugar fizzy drink
• Five or six jelly babies
• Three or four teaspoons of sugar or honey

Diet and zero-sugar drinks will not work, and chocolate is too slow — the fat delays absorption. Wait 10 to 15 minutes and recheck. If glucose is still below 4 mmol/L, repeat. Once they have recovered, offer a slower-release snack such as a slice of bread, a couple of biscuits or a glass of milk, unless a meal is due within the hour.

Never give food or drink to someone who is drowsy or unable to swallow — they may choke. Instead, place them in the recovery position, call 999, and use a glucagon injection if one is available and you have been shown how to give it. Do not give insulin during a hypo.

When High Blood Sugar Turns Serious

Hyperglycaemia tends to creep in: thirst, frequent trips to the toilet, tiredness, blurred vision and headaches over a day or more. Drinking water and following the person's own sick-day plan, which may include extra insulin, is usually enough.

Call 999 if you see any of these:

• Nausea, vomiting or abdominal pain
• Deep, rapid breathing
• Breath that smells fruity, or of nail polish remover
• Drowsiness, confusion or difficulty staying awake

These suggest diabetic ketoacidosis or a similar emergency needing hospital treatment. Keep the person warm, offer sips of water if they can swallow, and do not leave them alone.

If You Are Not Sure What Is Happening

When you cannot tell whether glucose is high or low, treat it as a hypo — provided the person is conscious and able to swallow. Low blood sugar harms quickly, and a small amount of sugar will not cause lasting damage even if their glucose turns out to be high. Never give insulin unless it is part of their own agreed routine, and never put anything in the mouth of someone who is unresponsive. If they are not breathing normally, start CPR, ask someone to fetch a defibrillator and call 999.

Being Prepared at Home

• Keep a hypo kit in the kitchen, in a handbag or rucksack, and in the car — glucose tablets, full-sugar drinks and in-date glucagon.
• Write down the essentials and stick them on the fridge: type of diabetes, medication, GP and hospital contacts, next of kin, and what to do in an emergency.
• Tell the people around you. Neighbours, work first-aiders, club leaders and school staff can all be briefed in a few minutes.
• Check before driving and never set off below 4 mmol/L. UK guidance advises waiting 45 minutes after glucose returns to normal before driving, with fast-acting sugar within reach.
• Take care with alcohol, which can mask a hypo and trigger one overnight. Eat carbohydrate alongside it and check glucose before bed.
• Review supplies regularly. Replace out-of-date glucose tablets and glucagon, and refresh your confidence in using them.

A calm, prepared household is the best safety net there is — and it takes very little to build one.