Most days, diabetes fits into your usual routine: meals, movement, medicines and perhaps an HbA1c test every few months. Illness – such as flu, a chest infection, sickness and diarrhoea, or COVID-19 – can suddenly make everything more complicated.

You may hear your team talk about “sick day rules” – a written plan that explains what to do with your diabetes medicines, food, fluids and blood sugar checks when you are unwell. This plan should come from your GP or diabetes team and may look slightly different for each person.

This article:

• Explains the idea of sick day rules in plain language.
• Describes how illness can affect your blood sugar.
• Gives examples of common red-flag symptoms where you should seek urgent help.
• Shows how to use this information alongside, not instead of, your NHS plan.

It links with our other diabetes pieces to give you a joined-up picture:

HbA1c & Daily Life  ·  First Year After Diagnosis  ·  Diabetes Medicines  ·  Mood & Motivation

What Do “Sick Day Rules” Actually Mean?

Sick day rules are simply special instructions for when you are unwell. They usually cover:

• Which diabetes medicines you should continue, reduce or temporarily pause.
• How often to check your blood sugar (and sometimes ketones, if you use insulin).
• What to do about food if you do not feel like eating.
• How much fluid to aim for.
• When to contact your GP, diabetes team or NHS 111.

They exist because illness can make your body behave differently. For example:

• You may not feel like eating, which can increase the risk of low blood sugar (hypos) if you use certain tablets or insulin.
• Infections can make blood sugar rise, even if you are eating less.
• Vomiting and diarrhoea can lead to dehydration and kidney strain, especially if you take specific blood pressure or diabetes medicines.

Your sick-day rules should be written down and tailored to your medicines and other health conditions. If you do not have a written plan, it is reasonable to ask your GP or diabetes nurse for one at your next review.

How Illness Can Change Your Diabetes Control

When you are unwell, your body releases stress hormones to fight the infection or recover from the problem. These hormones can:

• Raise blood sugar, even if you eat less than usual.
• Make your body more resistant to insulin.
• Leave you feeling very tired, foggy or thirsty.

At the same time, practical things can get harder:

• You may forget or struggle to take medicines on time.
• You may find it difficult to keep up with blood sugar checks.
• Cooking, shopping and drinking enough fluid may feel overwhelming.

That is why your sick-day plan may ask you to:

• Check your blood sugar more often than usual.
• Adjust the timing or dose of certain medicines.
• Focus on “easy” foods and fluids that you can manage when your appetite is poor.

Our articles on HbA1c & Daily Life and Building a Diabetes-Friendly Plate on a Budget can help you understand the bigger picture of tests and food choices on steady days.

Common Elements of Sick-Day Rules (General Education)

Every plan is different, but many NHS sick-day guidelines will include some of the following themes. These are educational examples only – always use your own plan first.

1. Medicines

You may be advised to:

• Continue most diabetes tablets and insulin, but adjust doses if you are eating less.
• Temporarily stop certain tablets that affect the kidneys, blood pressure or fluid balance if you are vomiting, have diarrhoea or cannot drink normally.
• Never stop insulin completely without specialist advice if you use it.

Our Medicines for Type 2 Diabetes – What They’re Trying to Do article can help you prepare questions about your specific tablets and sick-day rules.

2. Blood Sugar Checks

Your plan may suggest:

• Checking your blood sugar more often (for example every 2–4 hours during the day).
• Recording readings in a notebook so you can share them with your team.
• Looking out for patterns of consistently high or low readings.

3. Food and Fluids

Common advice includes:

• Trying small, frequent sips of fluid (water, sugar-free drinks, or special drinks suggested by your team).
• Choosing simple, easy foods – such as soup, yoghurt, toast – if you can manage them.
• Seeking help early if you cannot keep any fluids down or have ongoing diarrhoea.

Red-Flag Symptoms – When Illness May Be Urgent

While minor illnesses can often be managed at home with support, some symptoms suggest that your body may be under too much strain. You should seek urgent help (for example from NHS 111, an urgent GP appointment or 999 in an emergency) if you have diabetes and notice:

• Chest pain that is severe, tight, heavy or spreading to your arm, neck or jaw.
• Severe breathlessness, struggling to speak in sentences, or breathing that is fast and deep in an unusual way.
• Confusion, drowsiness or sudden change in behaviour, especially if you are usually clear-minded.
• Very high blood sugars that stay high despite following your plan (for example readings that remain much higher than your usual range – your team should specify numbers for you).
• Signs of dehydration that are getting worse – such as very little urine, dizziness when you stand, or a very dry mouth – especially if you cannot keep fluids down.
• Persistent vomiting (for example, being sick several times and unable to hold down any fluid).
• Severe abdominal pain that is not settling.
• High temperature with shaking, feeling very unwell, or any signs of sepsis (feeling very hot or very cold, confused, breathless or having mottled skin).

If you are unsure whether your symptoms are serious, it is safer to call NHS 111 or your GP practice for advice. They can help decide whether you need same-day assessment or emergency care.

Living Alone with Diabetes on Sick Days

Being unwell is harder when you live alone. There may be no one to notice if you become confused, dehydrated or unsteady on your feet. It can help to plan ahead:

• Keep your sick-day plan somewhere obvious – for example on the fridge or beside your medicine cupboard.
• Let a trusted person know when you are unwell and agree that they will check in by phone.
• Have a small supply of easy foods and drinks that keep well, ready for times when you cannot shop.
• Keep important numbers (GP, NHS 111, out-of-hours, trusted friend) written by the phone.

Our article Diabetes, Mood and Motivation – When You Feel Tired of Trying also explores how it feels to manage diabetes alone and offers ideas for emotional support.

How PHAT Can Support You Between Appointments

PHAT’s gentle Zoom exercise and education sessions are not an emergency service and cannot replace NHS sick-day advice. However, they can:

• Help you build confidence in understanding your condition before you become unwell.
• Give you a regular space to ask general questions about day-to-day routines (within our educational role).
• Encourage you to prepare your sick-day plan in advance so you are not searching for information when you feel poorly.

Our article How Our Zoom Exercise Sessions Fit Into Your Diabetes Care explains how movement and routine can support blood sugar, walking tolerance and mood on your steadier days.

Ten Practical Steps to Prepare for Sick Days

You do not need to do all of these at once. Pick one or two that feel manageable this month:

1. Ask for a written sick-day plan. At your next review, say: “Could we write down my personal sick-day rules for my diabetes medicines?”
2. Keep it visible. Put a copy where you and others can easily see it – fridge, medicine shelf, near your bed.
3. Make a “sick-day box”. Include a thermometer (if you use one), easy foods, oral rehydration sachets if advised, and a notepad and pen.
4. List your medicines clearly. Write the names, doses and times you take them. This helps professionals give better advice if you call.
5. Store key phone numbers together. GP, NHS 111, pharmacy, diabetes team (if you have one), trusted friend or family member.
6. Agree a check-in partner. Ask someone you trust to call or message you daily if you let them know you are unwell.
7. Practise using your meter. If you have a blood sugar meter, make sure you remember how to use it before you become poorly.
8. Know your “usual” numbers. Write down your typical blood sugar range and latest HbA1c so you can compare during illness.
9. Plan for mood as well as body. Decide one comforting activity (music, radio, PHAT video) for days when you feel low and unwell.
10. Review after you recover. When you feel better, note what worked, what didn’t, and what questions to ask next time you see your team.