If someone with diabetes is unconscious, having a seizure, or cannot swallow safely, call your local emergency number now. Do not put food or drink in their mouth. Everything else in this chapter can wait until you are calm and safe.

Emergencies in diabetes fall into two families. Too little glucose (hypoglycaemia) can cloud thinking within minutes and is the more common emergency in people who take insulin or certain tablets. Too much glucose with too little insulin, or a dangerous build-up of acids called ketones, develops over hours to days and is the second. You met both ideas in earlier chapters: lows after exercise in Chapter 9, and night-time lows and sick-day warnings in Chapter 10. This chapter puts the practical steps in one place.

Section 13.1 covers low glucose: what it is, how to treat it, and how to prevent it. Section 13.2 covers the high-glucose emergencies, ketones, sick days, and the newer medicine-related twist in which the glucose can look almost normal. Section 13.3 looks at other situations that disrupt routine: disasters, travel, fasting, and surgery. Section 13.4 gives you a card to fill in and carry, with one key sentence in ten languages.

13.1 Low Blood Glucose: Recognise, Treat, Prevent

What counts as a low

The American Diabetes Association (ADA) grades hypoglycaemia in three levels.[@ada2025s6]

Levels and thresholds as worded in the ADA Standards of Care 2025 (the 2026 edition could not be read in full; see the chapter notes).[@ada2025s6]

Notice that level 3 is defined by what happens to you, not by a number. If you cannot help yourself, it is severe, whatever the meter says.

Recognising it

Early warning signs are the body's alarm system, the stress hormones you met in Chapter 10. The ADA lists feeling shaky, nervous or anxious, sweating, chills and clamminess, irritability, confusion, a fast heartbeat, light-headedness, hunger, and nausea, with vision changes, tingling, and headaches also possible, and seizures in severe cases.[@adahypo] Diabetes UK adds going pale, tingling lips, tearfulness, tiredness, difficulty concentrating, and night sweats.[@diabetesukhypo] Everyone's pattern is a little different. Learn your own, and tell the people around you.

Lows happen mainly with insulin and with medicines that push the body to release its own insulin, such as sulfonylureas. The prescribing information for one widely used injectable medicine, for example, warns that combining it with insulin or a sulfonylurea may increase the risk of hypoglycaemia, including severe hypoglycaemia.[@ozempic2025] If you take neither, lows are far less likely; if you do, this section is for you and the people you live with.

When the warning signs fade

Some people stop feeling the early signs. The ADA calls this impaired awareness of hypoglycaemia: the body no longer releases the usual warning hormones at low glucose, which often happens with long-standing diabetes or repeated lows. It recommends screening for it at least once a year and notes that several weeks of avoiding lows, typically by temporarily relaxing glucose targets, can improve awareness.[@ada2025s6] That is a decision for you and your care team, not something to do alone. The ADA also recommends a continuous glucose monitor for people at high risk of hypoglycaemia; Chapter 12 explains how alarms work.[@ada2025s6]

The 15-15 rule

For a conscious person who can swallow, the ADA's wording is: consume 15 grams of fast-acting carbohydrate, wait 15 minutes, then recheck your glucose.[@adahypo] The ADA's 2025 Standards say the same: for most people, 15 grams of carbohydrate, recheck after 15 minutes, and repeat if the low persists. They also note that people using automated insulin delivery systems may use smaller amounts, 5 to 10 grams, which is something your team will tell you.[@ada2025s6] Diabetes UK advises 15 to 20 grams, a rest of 10 to 15 minutes, and repeating if the reading is still below 4 mmol/L.[@diabetesukhypo] Different bodies, slightly different numbers, the same idea: fast sugar, then check, then repeat if needed.

The ADA gives these examples of about 15 grams: glucose tablets (it gives 4 to 5 grams of carbohydrate per tablet, so about 3 to 4 tablets, a number calculated for this book), one packet of glucose gel, half a cup (4 ounces, about 120 mL) of juice or regular soda (not diet), or 1 tablespoon of sugar or corn syrup, and honey only for people older than one year.[@adahypo] Diabetes UK's list for the UK is five glucose tablets, four jelly sweets, a small sugary drink of 150 to 200 mL, or a 200 mL carton of pure fruit juice.[@diabetesukhypo]

Drinks differ in how much sugar they hold, so read the label. The table below shows how much of a drink gives 15 or 20 grams when a label lists a given number of grams of sugar per 100 mL.

Volumes were calculated as grams needed divided by grams per 100 mL, times 100, and rounded. The sugar values are examples of label figures, not measurements of particular brands. Diet and "zero sugar" drinks do not work for treating a low.

Two practical points follow. First, take the sugar promptly; do not wait to prepare a meal. Second, once your glucose is back up, ask your team whether you should follow with a snack or a meal. If you feel worse, or are still low after two rounds, get help.

{{fig:F13-A}}

When someone cannot help themselves

If a person is confused to the point of not cooperating, very drowsy, having a seizure, or unconscious, they are in level 3 territory. The steps are:

• Do not put food or drink in their mouth. A paediatric guideline from the International Society for Pediatric and Adolescent Diabetes (ISPAD) states that sugar or thin liquids such as a glucose solution or honey should not be given forcibly to a semi-conscious or unconscious child.[@abraham2022] The same reasoning applies to adults: the risk is choking.
• Call your local emergency number. Diabetes UK advises calling an ambulance if there is no glucagon available or if there is no recovery within 10 minutes.[@diabetesukhypo] The safest rule for lay readers is simpler: unconscious, seizure, or cannot swallow means call emergency services at once.
• Place the person on their side in the recovery position (on the side, head tilted back, knees bent), as Diabetes UK describes.[@diabetesukhypo]
• Give glucagon if it is available and someone knows how.

Glucagon

Glucagon is a hormone the pancreas makes to raise glucose by telling the liver to release stored sugar (Chapter 1).[@amin2025] As a rescue medicine it comes in forms that can be given by another person: an injectable kit in which a powder is mixed with liquid, a nasal powder, and ready-to-use pens or auto-injectors.[@abraham2022] The ADA recommends that glucagon be prescribed for everyone who takes insulin or is at high risk of hypoglycaemia, and that family, caregivers, and others who support you know where it is and be trained to give it. It prefers prefilled pens or syringes to powders that must be mixed.[@ada2025s6] Glucagon often causes nausea and vomiting as the person wakes up,[@abraham2022] so keep them on their side and stay with them. This book does not give doses. Your pharmacist or care team will teach the exact steps for the product you own; ask them to teach your family too, and check the expiry date.

Even after glucagon works, medical review is wise. A person who has needed rescue has had a severe event, and your care team needs to know why it happened.

Why it happens, and what helps

Common triggers are a missed or delayed meal, more activity than usual (lows can appear 6 to 15 hours after exercise and the risk can last up to 48 hours),[@colberg2016] alcohol, and medicine changes. Sulfonylureas can interact with some common antibiotics in ways that raise the effective dose and cause lows.[@ada2025s6] Ask your pharmacist to check any new prescription against your diabetes medicines. The ADA also lists older age, chronic kidney disease, heart disease, alcohol or substance use disorder, and cognitive impairment among risk factors, and recommends that your history of lows be reviewed at every visit.[@ada2025s6]

Night-time lows. In Chapter 10 you saw that a night low can pass unnoticed, or show only as a morning high, sweats, nightmares, or a headache. ISPAD notes that night lows can present as confusion, nightmares, or seizures during the night.[@abraham2022] Sensors can reveal lows that cause no symptoms.[@ada2026s6] In 755 sensor users with type 1 diabetes over 14 days, about one in three had at least one night-time low followed by a high before 6 a.m.[@gonzalezvidal2025] Practical steps: use a sensor with a low alarm if one is available; ask your team whether a bedtime snack is appropriate, since the ADA mentions a bedtime snack for preventing overnight lows only when specifically needed;[@ada2025s6] and tell your team about repeated night sweats or morning headaches. Do not change your evening medicine on your own.

Alcohol. The ADA notes that lows can strike hours after your last drink, especially after exercise, because the liver prioritises processing alcohol over releasing glucose; that combining alcohol with insulin or sulfonylureas can cause lows; that eating while you drink protects better than drinking sugary mixers; and that lows can look like drunkenness, with slurred speech, drowsiness, or confusion, which makes them easy to miss. For people with impaired awareness, drinking is especially risky.[@adaalcohol] Tell the people you drink with that you have diabetes and what to do.

Driving. An ADA statement advises checking glucose before driving and at regular intervals on drives of an hour or more, avoiding driving with a low-normal glucose (70 to 90 mg/dL, 3.9 to 5.0 mmol/L) without first eating carbohydrate, stopping the vehicle as soon as symptoms appear, and not driving again until glucose is in a safe range, usually after 30 to 60 minutes, because thinking recovers more slowly than the meter number. Carry a meter and quick-acting sugar in the car, and see a clinician if your awareness of lows is fading.[@lorber2014] Local laws differ, and in some countries you must tell the licensing authority if you use insulin or have disabling lows; ask your care team.

Science Corner: Why the brain gives up first The brain uses glucose as its main fuel and holds almost no reserve. When glucose falls, the body first releases adrenaline, which causes the shaking, sweating, and racing heart, and then, if glucose keeps falling, the brain itself runs short of fuel, causing confusion, slurred speech, and eventually seizure or unconsciousness. When the early alarm no longer sounds (impaired awareness), the first sign can be confusion, and by then you may not be able to treat yourself. That is why other people need to know what to do.

13.2 High Glucose Crises: Ketones, Sick Days, and DKA

Two emergencies

When there is not enough insulin, the body cannot use glucose and starts burning fat, releasing ketones, acids that at high levels make the blood dangerously acid. This is diabetic ketoacidosis (DKA). It is most often linked with type 1 diabetes (Chapter 3), but it can occur in type 2 diabetes too. A second crisis, the hyperosmolar hyperglycaemic state (HHS), occurs when glucose becomes extremely high and the body becomes severely dehydrated, usually without much ketone build-up.

A 2024 international consensus report describes them this way: DKA means glucose of at least 200 mg/dL (11.1 mmol/L) or a history of diabetes, together with beta-hydroxybutyrate (a blood ketone) of at least 3.0 mmol/L and acidosis. HHS means glucose of at least 600 mg/dL (33.3 mmol/L), high blood osmolality (the blood becomes very concentrated), ketones below 3.0 mmol/L, and no severe acidosis. Common symptoms are frequent urination, extreme thirst, weight loss, dehydration, nausea, vomiting, abdominal pain (more common in DKA), deep laboured breathing, and mental changes. Triggers include infection (the most frequent), missed insulin, acute illness, and some medicines such as SGLT2 inhibitors and glucocorticoids (steroids).[@umpierrez2024] You will not diagnose yourself with these numbers, and you do not need to. Hospitals do that. Your job is to recognise the pattern and get help early.

Ketone testing: what the numbers mean

Blood ketone meters and urine strips are available in many countries. UK sick-day guidance for adults with type 1 diabetes, prepared by TREND-UK, sets out this ladder for blood ketones:[@trend2018]

Thresholds as printed in TREND-UK sick-day guidance for type 1 diabetes (prepared February 2018). The same guidance counts 2+ on a urine strip as a sign that DKA is likely developing. These are adult type 1 rules; your team's advice for you, for a child, or in pregnancy takes priority.[@trend2018]

These fit with the rule in Chapter 9: the ADA exercise statement advises checking ketones if glucose is 250 mg/dL (13.9 mmol/L) or more, and postponing exercise if blood ketones are 1.5 mmol/L or higher or urine ketones are moderate or large.[@colberg2016] The ADA also advises measuring ketones during illness, especially when glucose is above 200 mg/dL (11.1 mmol/L).[@ada2026s6]

{{fig:F13-B}}

Sick-day rules

Illness raises glucose even when you are not eating. The ADA warns that stressful events such as infection, injury, or surgery raise the risk of both highs and lows and can trigger crises, and that people on intensive insulin should not stop background (basal) insulin just because they are not eating.[@ada2026s6] TREND-UK states the same point in capitals: do not stop your insulin even if you are unable to eat.[@trend2018] Instead, ask your team, before you are ill, for written sick-day instructions. The core points, from the sources above and general practice, are:

1. Keep taking your usual background medicine unless your team has told you otherwise, and call for advice rather than deciding alone. Do not stop insulin because you are not eating.
2. Check glucose and, if you are at risk of DKA, ketones more often. TREND-UK advises every 4 to 6 hours when ketones are below 1.5 mmol/L, and every 2 hours once they reach 1.5 mmol/L or more.[@trend2018]
3. Drink. TREND-UK advises sugar-free fluids of at least 2.5 to 3.5 litres (4 to 6 pints) over 24 hours, and at least 100 mL an hour when ketones are present, unless your team has given you a different limit, for example for heart or kidney problems.[@trend2018]
4. Get medical help urgently for vomiting so that you cannot keep fluids down, drowsiness or breathlessness, severe abdominal pain, ketones that stay high, or ketones during pregnancy.[@trend2018] The 2024 consensus adds that deep laboured breathing and mental changes are warning signs.[@umpierrez2024]

Vomiting with ketones, difficulty breathing, confusion, or drowsiness is an emergency. Call emergency services or go to hospital.

Euglycaemic DKA and SGLT2 inhibitors

SGLT2 inhibitors are medicines that lower glucose by making the kidneys pass glucose into the urine (Chapter 11). They have another effect that matters here: DKA can develop when the glucose is not very high. The 2024 consensus reports that about 10 percent of people with DKA have euglycaemic DKA, with glucose below 200 mg/dL (11.1 mmol/L), and that SGLT2 inhibitors account for most such cases.[@umpierrez2024] A US prescribing label for one SGLT2 inhibitor says that ketoacidosis can occur with blood glucose below 250 mg/dL, lists nausea, vomiting, abdominal pain, generalised malaise, and shortness of breath as symptoms, tells clinicians to assess for ketoacidosis whatever the glucose level, and tells patients to stop the medicine and seek medical attention immediately if the signs appear.[@farxiga2024]

Science Corner: Why a "normal" number can hide DKA Ketoacidosis is defined by the acids, not the glucose. If the kidneys are dumping glucose into the urine because of an SGLT2 inhibitor, the blood glucose can sit lower than in classic DKA, even though ketones are climbing. Someone who relies on the glucose alone may be reassured and delay. The safeguard is to act on the symptoms, especially nausea, vomiting, abdominal pain, unusual tiredness, and fast or laboured breathing, and to test ketones if you have the means, whatever your glucose reading says.[@farxiga2024]

Your prevention plan should be agreed with your care team in advance: when an SGLT2 inhibitor should be held (for example before surgery or prolonged fasting, or if you become unwell), and how to restart. Do not improvise that plan yourself.

Vomiting, dehydration, and injectable medicines for weight and glucose

Vomiting and diarrhoea lower fluid volume and can strain the kidneys. The label of one GLP-1 receptor agonist warns that nausea, vomiting, or diarrhoea can cause dehydration leading to acute kidney injury and advises monitoring kidney function in people with such reactions.[@ozempic2025] If you take a medicine of this kind and cannot keep fluids down, contact your team the same day, and go to hospital if you are also drowsy, breathless, or passing very little urine.

When to go to hospital

Call emergency services or go to hospital for any of these: unconsciousness, a seizure, or a level 3 low; vomiting with high ketones; difficulty breathing; confusion or drowsiness with high glucose; ketones at 3.0 mmol/L or higher (or 2+ in urine); or any illness where you cannot keep fluids down. HHS, which is seen mainly in older adults with type 2 diabetes, tends to build up over days; the consensus lists dehydration and mental changes among its features.[@umpierrez2024] If you are unsure, call. Emergency staff would prefer an unnecessary call to a late one.

13.3 Other Emergency Situations

Power cuts, floods, conflict, and other disruptions

Ketones and exercise also mix badly: as Chapter 9 explained, postpone exercise when blood ketones are 1.5 mmol/L or higher, and do not exercise when ill or vomiting.[@colberg2016] In a disaster you may lose electricity, clean water, pharmacies, and your home. The ADA suggests storing at least a week's worth of diabetes supplies: oral medication, insulin, insulin delivery supplies, lancets, extra batteries for meter or pump, a quick-acting source of glucose, and an extra glucagon kit if you have one, kept in an easy-to-identify container in a place that is easy to reach. It also advises wearing medical identification and keeping a list of emergency contacts.[@adaprep]

Insulin without refrigeration. The US Food and Drug Administration (FDA) says that insulin vials or cartridges supplied by manufacturers, whether opened or not, may be left unrefrigerated at temperatures between 59 and 86 degrees Fahrenheit (15 to 30 degrees Celsius, converted by calculation) for up to 28 days and continue to work. Insulin that has been diluted or removed from its original vial should be discarded within two weeks; insulin that has been frozen should not be used; and insulin in pump infusion sets should be discarded after 48 hours or if exposed to temperatures above 98.6 degrees Fahrenheit (37 degrees Celsius).[@fdainsulin2017] The ADA adds that insulin loses some effectiveness in extreme temperatures and should be kept away from direct heat and sunlight, and that if you use ice you should avoid freezing the insulin.[@adainsulin2018] Check the leaflet for your own product: this rule is written for the manufacturer-supplied vials and cartridges the FDA discusses, and pens and newer products may carry their own instructions.

Science Corner: How much heat can insulin take? A 2023 Cochrane review of mostly laboratory studies on human insulin (not the newer analogue insulins) found that unopened vials and cartridges could be stored at up to 25 degrees Celsius for a maximum of six months and at up to 37 degrees Celsius for a maximum of two months without a clinically relevant loss of potency. The review could not rate the certainty of the evidence because no validated method exists, and almost all data came from laboratories.[@richter2023] The lesson: short periods of warmth are usually survivable, but in a real heat wave, check your blood glucose more often, because unexplained highs may mean your insulin has weakened. If in doubt, ask a pharmacist and replace it.

Travel

Carry all diabetes supplies in your hand luggage, more than you expect to need, plus fast sugar, glucagon if prescribed, and a letter from your doctor if your country or airline requires one. Keep insulin out of checked luggage where it can freeze in the hold. Wear or carry the emergency card in 13.4. These are common practice recommendations; ask your team about time-zone changes.

Ramadan and other fasts

Chapter 7 introduced the assessment six to eight weeks before Ramadan. The IDF-DAR guideline says education should include when to break the fast, and lists hypoglycaemia, hyperglycaemia, dehydration, and DKA among the hazards of fasting.[@idfdar2021] A 2020 set of recommendations for managing diabetes during Ramadan states that fasting should be stopped if there are symptoms of hypoglycaemia, hyperglycaemia, dehydration, or acute illness, and gives thresholds of below 70 mg/dL (3.9 mmol/L) or above 300 mg/dL (16.6 mmol/L), and it adds that testing your glucose during fasting does not break the fast, a common misconception.[@ibrahim2020] Breaking the fast for a low or for illness is treating a medical problem, not failing. Treat a low as in 13.1, drink, and speak with your care team and your religious adviser. Anyone on insulin or a sulfonylurea should have a written plan before Ramadan begins; this book does not give medicine changes.

Surgery and procedures

Tell every surgeon, dentist, and anaesthetist that you have diabetes and list your medicines. The US label for the SGLT2 inhibitor mentioned above says to withhold it for at least 3 days, if possible, before major surgery or procedures with prolonged fasting,[@farxiga2024] which is one reason your team needs early notice of planned procedures. Do not stop or restart any medicine on your own; ask for a written plan. The ADA also notes that surgery is a physical stress that can raise the risk of highs and lows.[@ada2026s6]

Pregnancy

Pregnancy changes insulin needs and the risk of ketones. The TREND-UK guidance lists ketones during pregnancy among the reasons to seek hospital care.[@trend2018] The IDF-DAR guideline lists pregnant women with diabetes among the groups at particular risk when fasting (Chapter 7).[@idfdar2021] Plan any pregnancy with your diabetes team before it starts, and call them the same day for vomiting, ketones, or repeated lows.

13.4 Your Emergency Card

A card cannot treat a low, but it can speak for you when you cannot. Copy the template below onto a card, or type it and print it, then keep a copy in your wallet or phone case, one in your bag, and one on the fridge. If you use a phone, add the same text to your lock-screen medical ID.

The template

Blank fields to complete yourself.

The emergency number differs by country. The European Union's official information site says 112 is the number you can dial free of charge from fixed and mobile phones everywhere in the EU, and that it works in all EU countries and many other countries in Europe and worldwide.[@eu112] Outside the EU, look up your local number now and write it on the card.

The key sentence, in ten languages

Write the sentence in the language of the place you live and the places you travel to. The English version reads: "I have diabetes. If I am confused, very sleepy or unconscious, my blood sugar may be too low. If I can swallow, give me sugar or juice. If not, call emergency services."

These translations were produced without a native-speaker check. Ask a fluent speaker, ideally one familiar with medical wording, to verify them before you print or carry the card. Arabic is written right to left; make sure your printing tool keeps that direction. The Arabic uses masculine forms and the Spanish, French, Portuguese, Russian, and Hindi use slash or bracket forms for gender, so change them to suit the person carrying the card. "Juice" means a sugary drink, not diet or unsweetened.

Add one extra line if it applies to you: "I use insulin" or "I take a medicine that can cause low blood sugar." If you take an SGLT2 inhibitor, add "If I am vomiting, breathless or very unwell, my blood sugar may be normal but I may still have ketoacidosis." Show your card to your family and workmates, and tell them where your glucagon is.

Key Takeaways

• Level 1 is glucose below 70 mg/dL (3.9 mmol/L), level 2 is below 54 mg/dL (3.0 mmol/L), and level 3 is any low that leaves you needing another person's help, whatever the number.
• For a conscious person who can swallow, take about 15 grams of fast-acting carbohydrate, wait 15 minutes, recheck, and repeat if still low; some guidance uses 15 to 20 grams and a 10 to 15 minute wait.
• A person who is unconscious, having a seizure, or unable to swallow needs emergency services, and nothing in the mouth; glucagon, given by someone trained, is the rescue medicine.
• Night lows, alcohol, delayed lows after exercise, and fading awareness are the situations that catch people out; sensors, snacks agreed with your team, and telling others all help.
• During illness, do not stop background insulin because you are not eating, drink plenty, check glucose and ketones more often, and get help early; ketones of 3.0 mmol/L or more, or vomiting with high ketones or breathing difficulty, are emergencies.
• DKA can occur with glucose below 250 mg/dL in people taking SGLT2 inhibitors (a consensus report defines euglycaemic DKA as below 200 mg/dL), so act on symptoms and not only on the meter.
• Prepare before you need it: a week of supplies, insulin kept cool, a written sick-day plan, a filled-in emergency card, and someone who knows where the glucagon is.

Action Points

1. Write your emergency number on your card today. Look up the local number, fill in the template in 13.4, and put copies where you will find them.
2. Put fast sugar in three places. Keep glucose tablets or a sugary drink in your bag, by your bed, and in your car, and check the expiry dates and the amount on the label.
3. Ask your care team three questions. Do I need glucagon and who should be trained; what are my personal sick-day rules and ketone thresholds; and, if I take an SGLT2 inhibitor or sulfonylurea, what should I do when I am vomiting or fasting?
4. Train one other person. Show a family member, friend, or workmate the recovery position, where your glucagon is, and when to call emergency services.
5. Build a week's kit. Pack a week of supplies and a medicine list, and write down how you will keep your insulin cool if the power fails.

This book is intended for education and does not replace personal medical advice. If you have diabetes or take glucose-lowering medication, please consult your healthcare team before changing your diet, exercise, or treatment.