The short answer
- Keep drinks going all daySugar-free drinks, sipped through the day. Diabetes UK says to eat little and often if meals are too much, with some carbohydrate for energy.
- Check more often if they testDiabetes UK says at least every four hours while unwell, overnight too, or as their team advises. Write each reading down.
- Ask for written sick day rules nowSome medicines may need pausing during vomiting, diarrhoea or dehydration. Only the GP, nurse or pharmacist can say which, so ask them while your relative is well.
- Cannot keep drinks down means getting helpRing the diabetes team, GP or 111. Drowsiness, confusion, fast breathing or fruity-smelling breath with high blood sugar means 999.
Checked against NHS, Diabetes UK and TREND Diabetes guidance on 9 October 2026. This page describes England and is general information, not medical advice. Your relative's own diabetes team's plan comes first.
This guide is part of our health conditions section, and it sits with diabetes at home, which covers the day-to-day side. Here the subject is the bad days: a cold, a chest or urine infection, a stomach bug, or a temperature that keeps somebody in bed. With a little planning, a bad day can be looked after at home and the warning signs caught early.
Why illness upsets diabetes
Why being ill makes blood sugar harder to manage
When the body is fighting an infection it responds less well to insulin. TREND Diabetes, a group of diabetes nurses who write leaflets for patients, puts it simply: being unwell usually makes glucose levels rise, even if you are eating less than usual.
Infection pushes blood sugar up
The usual direction
Eating very little can bring it down
If they take insulin or gliclazide
Fever, sickness and diarrhoea dry the body out
Dehydration
Some medicines behave differently
While somebody is dehydrated
The two directions can happen in the same person on the same day, which is why checking matters more than guessing. Somebody with type 2 diabetes who takes metformin on its own is less likely to go low, while somebody on insulin can swing either way. If you are not sure which type your relative has or what each of their medicines is for, what is diabetes? explains the types and treatments in plain terms.
An ordinary illness can also tip into one of two emergencies caused by very high blood sugar. Diabetic ketoacidosis, or DKA, mostly affects people with type 1 diabetes and people with type 2 who take insulin. Hyperosmolar hyperglycaemic state, or HHS, mainly affects people with type 2. Both are explained in the section on when to ring for help, with the signs to look for.
Drinks, food and checks
Keep drinks and small meals going, and check more often
On a sick day the everyday work comes down to drinking enough, eating a little when they can, keeping to their usual medicines unless told otherwise, and writing down what happens.
- Morning
Medicines as usual unless the plan says otherwise
Diabetes UK says to keep taking diabetes medicines even if they do not feel like eating, unless they have been told to stop. If there are written sick day rules, this is the moment to look at them.
- All day
Sugar-free drinks, sipped
Water or sugar-free squash, a few mouthfuls at a time. TREND suggests sipping gently through the day and aiming for at least 2½ to 3½ litres in 24 hours, but if they have been told to limit fluids for their heart or kidneys, ask the GP what applies.
- Mealtimes
Something small with some carbohydrate
If a meal is too much, a small bowl of soup, a glass of milk, a yoghurt or a plain biscuit. TREND lists foods like these as easy ways to keep some energy going.
- Every 4 hours
A check, if they test, and the number written down
Diabetes UK says at least every four hours, including overnight, or as their team advises. If they do not test, watch for thirst, passing more urine and tiredness.
- Any time
Ring early if it is not settling
Diabetes UK says to contact the diabetes team as soon as somebody feels ill. Being unable to keep drinks down needs medical help urgently.
Diabetes UK's phrase is little and often, and it works for drinks as well as food. When somebody feels sick, a few mouthfuls offered every time you pass are easier to manage than a large glass every few hours. If drinks are not going down, dark urine and passing less of it are signs of dehydration on the NHS list, and the symptoms of dehydration in older people sets out what to watch for.
Diabetes UK also suggests letting a fizzy drink go flat if they are being sick, as it can be easier to keep down. TREND says basic over-the-counter painkillers and cough syrups can be used for a temperature or a cough, need not be sugar-free, and that the pharmacist can advise. Show the pharmacist the list of prescribed medicines before buying anything new.
Written sick day rules
Ask the GP or pharmacist for written sick day rules before they are needed
Some medicines are best paused for a short while when somebody is being sick, has diarrhoea or is dehydrated, and then restarted when they are eating and drinking normally again. Which ones, and when, depends on the person. It has to come from the people who prescribe them, in writing, and nobody should stop a medicine on the strength of a website.
Our plan for an unwell day
Ask for this at the next diabetes review, while your relative is well. The answers are written in by the GP, the practice nurse, the diabetes team or the pharmacist, never by a website.
- Name
- Type of diabetes
- Date agreed
- Review by
1Their medicines
Which of their medicines carry on as normal when they are ill, even if they are eating very little?
Should any be paused if they are being sick, have diarrhoea or cannot keep drinks down? When do they restart?
If they take insulin or gliclazide, what should happen if blood sugar runs high, or if they are eating much less?
2Checking
Should they check their blood sugar more often while unwell, and how often?
Should they check for ketones? Is there a meter or strips in the house, and are they in date?
Which reading means ringing you, and which means ringing 111 or 999?
3Drinks and food
How much should they drink in a day while unwell? Is there a fluid limit because of their heart or kidneys?
What can they have for energy when a proper meal is too much?
4Who to ring
The number for the diabetes team or the practice nurse, and the hours it is answered.
Out of hours, NHS 111. Where the list of medicines is kept, so it can go with them to hospital.
5Who does what at home
If they cannot do their own checks or insulin while ill, who will? A carer can only do this after a nurse has trained them and agreed it in writing.
Who in the family is told when they are unwell, and who goes with them if they are admitted?
Keep the card with the list of medicines, somewhere anyone visiting can find it. Bring it to each review, because tablets change.
Several NHS areas print a card called medicine sick day rules. The one from NHS Somerset, for example, names groups that include some blood pressure tablets, water tablets, anti-inflammatory painkillers and certain diabetes medicines, says they are paused during vomiting, diarrhoea or dehydration, says to restart after 24 to 48 hours of eating and drinking normally, and tells people to ask their pharmacist, GP or nurse if in doubt. TREND's leaflet for type 2 diabetes makes the same point about some tablets and adds that people on insulin or tablets such as gliclazide may need their dose adjusted while ill. Those adjustments are the prescriber's to set.
So the useful thing a family can do is ask in advance. The next diabetes review, the annual medication review or a visit to the pharmacy are all good moments. Take the list of medicines and the questions on the card above, and ask for the answers to be written down. If your relative is on insulin, ask the diabetes nurse for their own written plan for illness, because insulin is adjusted for each person. The card belongs alongside the rest of the routine in a diabetes care plan for home, so everyone who helps knows where to find it.
When to ring for help
The signs that mean ringing the team, 111 or 999
Start with the diabetes team or the GP. A few signs mean ringing 111 straight away, and a few mean 999. These are taken from the NHS and Diabetes UK pages, in their words.
The diabetes team, practice nurse or GP
The same day- They are ill and nobody is sure what to do about their diabetes medicines
- Blood sugar is staying higher than usual, or above 15 mmol/l, if they check it
- You think they have an infection, or the illness is going on or getting worse
From Diabetes UK, TREND Diabetes
NHS 111, if you cannot reach their team
Now, by phone or online- They keep being sick and cannot keep drinks down
- Signs of dehydration: dark pee or much less of it, dizziness on standing that does not pass, unusual tiredness
- If they take insulin: blood sugar is high and the insulin is not bringing it down, or ketones are raised
From NHS: diarrhoea and vomiting, dehydration, diabetic ketoacidosis
999, or A&E
Straight away- High blood sugar with being sick or stomach pain, fast breathing, a fast heartbeat or high ketones
- Drowsy, hard to wake, or confused, or breath that smells fruity
- Blue, grey, pale or blotchy skin, lips or tongue, or skin that feels cold
From NHS: high blood sugar, dehydration
High blood sugar on its own usually comes on gradually, and the NHS lists thirst, passing more urine, tiredness, blurred vision and weight loss as the signs. If your relative tests and the reading stays above the level their team set, or above 15 mmol/l, Diabetes UK says to contact the team.
DKA, which mostly affects people who take insulinSection titled DKA%2C%20which%20mostly%20affects%20people%20who%20take%20insulin
The NHS says the symptoms of diabetic ketoacidosis usually develop over about 24 hours, sometimes faster. They include being very thirsty and passing more urine, stomach pain, feeling or being sick, diarrhoea, deep or fast breathing, breath that smells fruity, tiredness, drowsiness or confusion, and blurred vision. Some people have a meter that measures ketones as well as sugar, and the NHS page on diabetic ketoacidosis gives the readings that mean ringing the team or 111, and the reading that means 999. If they have the symptoms and you do not know their ketone level, the NHS says to ring 999 or go to A&E.
HHS, which mainly affects people with type 2Section titled HHS%2C%20which%20mainly%20affects%20people%20with%20type%202
Diabetes UK describes hyperosmolar hyperglycaemic state as a life-threatening complication that needs treating in hospital. It builds up over several days, from very high blood sugar and dehydration, sometimes with an infection behind it. The signs it lists are passing more urine, being very thirsty all the time, feeling sick, very dry skin, feeling generally unwell, and later confusion, sleepiness and gradually losing consciousness. New confusion during an illness is a reason to ring for help, and not something to put down to age.
Blood sugar can also go too low on a sick day, particularly if they take insulin or gliclazide and have barely eaten. Shaking, sweating, sudden confusion or unusual behaviour can be a hypo, and hypos in older people covers what the NHS says to do and when it is 999.
Vomiting and diarrhoea
Being sick or having diarrhoea needs help sooner
A stomach bug that a healthy adult would sleep off can unsettle diabetes quickly, because food and drink are not staying in and fluid is being lost. Diabetes UK says that if somebody with diabetes cannot keep any fluids down, they need medical help urgently.
What helps
- Small sips of water or sugar-free squash, which the NHS suggests when somebody feels sick
- A flat fizzy drink if that is easier to keep down, as Diabetes UK suggests
- Checking the written sick day rules, or ringing the GP or pharmacist, about any medicine that is paused during vomiting or diarrhoea
- A note of how many times they have been sick or had diarrhoea, and when they last passed urine
- Ringing 111 if they keep being sick and cannot keep drinks down, which is on the NHS list of reasons to call
What to avoid
- Waiting to see if it settles overnight when no drinks are staying down
- Stopping or halving a medicine because somebody is not eating, unless their written rules or a clinician say so
- Fruit juice and ordinary fizzy drinks for thirst, which the NHS says can make diarrhoea worse
- Leaving them alone for long stretches while they are being sick, especially if they are drowsy or unsteady
- Driving them to A&E yourself if they need to go. The NHS says to ask someone else to drive or ring 999
The NHS says vomiting usually stops in one or two days and diarrhoea within five to seven, and that vomiting for more than two days or diarrhoea for more than seven is a reason to ring 111. For somebody with diabetes those limits are a backstop rather than a target: TREND lists persistent vomiting and being unable to keep fluids down as reasons to ring the GP or diabetes nurse for immediate help.
Some people also need their other medicines looked at after a bout of illness, particularly if they take several for the heart, blood pressure or kidneys. Several conditions and many medicines explains how to ask for a structured medication review once they are better.
What a carer can do
What a carer can do on the days your relative is unwell
A carer does not treat diabetes, adjust medicines or decide whether a sick day rule applies. What a carer can do is be there more often while your relative is ill, keep drinks and food going, write down what happens, and ring for help early.
- 1
Extra visits while they are ill
For a few daysA lunchtime or teatime visit added for the days your relative is in bed means somebody sees them more than once a day, refills drinks and notices if they are getting worse. - 2
Drinks and small meals, offered and recorded
Every visitSips of a drink offered more than once, something small to eat, and a note of what went down and what came back up. - 3
Medicines prompted as the plan says
Every visitA carer can prompt and help with prescribed tablets as agreed, and write down what was taken. If there are written sick day rules, they follow them; if not, they help your relative ring the GP or pharmacist. - 4
Readings written down, not acted on
If they testIf your relative checks their own blood sugar, a carer can remind them and write the number in the notebook. Doing the test for them, or giving insulin, happens only where a nurse has trained that named carer and agreed it in writing. - 5
Ringing for help, and telling you
The same visitA carer can ring the team, 111 or 999 when a sign on the ladder above appears, and let the family know straight away.
Without that written delegation, insulin injections and blood sugar testing stay with your relative, the family or the district nurse. If your relative usually does their own insulin and is too unwell to manage it, ring the diabetes team or the surgery for a district nurse visit rather than asking a carer or a relative to guess.
If your relative lives alone and you cannot get there every day while they are ill, you can search for carers near you and compare their rates. You choose the carer, meet them first and agree the visits and the routine with them directly, and you can keep the same person afterwards. There is no way to search for carers by diabetes experience: what a carer says about their experience is their own account on their profile, so ask them about it when you talk. Every carer on PrimeCarers has had their identity and right to work checked, an enhanced DBS check (or PVG in Scotland, Access NI in Northern Ireland) issued within the last 2 years, and an online interview. Carers are insured while they work.
Questions
Questions families ask when someone with diabetes is ill
Diabetes UK says to keep taking diabetes medicines even if they do not feel like eating, unless they have been told to stop. Some medicines may need pausing during vomiting, diarrhoea or dehydration, and some doses may need changing, but only the GP, diabetes nurse or pharmacist can say which. Ask them for written sick day rules, ideally before your relative is ill, and ring them or 111 if there is no plan. Diabetes UK's guidance on illness has the general advice.
TREND Diabetes suggests sipping sugar-free fluids gently through the day, at least 2½ to 3½ litres (4 to 6 pints) in 24 hours. Somebody who has been told to limit fluids because of heart failure or kidney disease should ask their GP what applies to them. If no drinks are staying down, Diabetes UK says to get medical help urgently.
Both are emergencies caused by very high blood sugar. DKA, diabetic ketoacidosis, mostly affects people with type 1 diabetes and people with type 2 who take insulin, and the NHS says it usually develops over about 24 hours. HHS, hyperosmolar hyperglycaemic state, mainly affects people with type 2 and builds up over several days with severe dehydration. Both need hospital treatment.
Only where a healthcare professional, usually the district nurse, has trained that named carer and delegated the task in writing. Otherwise insulin and testing stay with your relative, the family or the nurse. A carer can prompt and help with prescribed tablets as agreed, write down readings your relative takes, offer drinks and food, and ring for help. Insulin at home explains the delegation.
You can search carers near you and message them about extra visits. If you need somebody quickly, the urgent care page explains how PrimeCarers can look for a carer for you, with a one-off fee of £40 charged only if you go ahead with a carer found that way. Carers on PrimeCarers charge £18 to £25 an hour with our fee included.
The client contract on PrimeCarers says a visit the client cancels is paid in full, except where the reason is unplanned hospitalisation, illness, or another reason the client and carer agree. Tell the carer as soon as you can. PrimeCarers charges nothing itself to cancel, but does not set the terms between you and the carer.