What are the sick day rules for diabetes?

The core sick day rules for diabetes are: 1) Never stop taking diabetes medication, 2) Check blood glucose every 2-4 hours, 3) Test for ketones if blood glucose exceeds 13 mmol/L (240 mg/dL), 4) Stay hydrated with at least 200ml fluid per hour, 5) Eat small regular portions of easily digestible carbohydrates, and 6) Contact your diabetes team if unsure about medications.

When should someone with diabetes seek emergency help?

Seek emergency help if: blood ketone levels are above 3.0 mmol/L, persistent vomiting prevents keeping fluids or medication down for more than 2 hours, blood glucose remains above 20 mmol/L (360 mg/dL) despite correction doses, signs of DKA appear (deep rapid breathing, fruity breath, abdominal pain), or confusion, drowsiness, or loss of consciousness occurs.

Why does illness affect blood sugar levels in diabetes?

When you're ill, your body releases stress hormones (cortisol, adrenaline, glucagon) as part of the immune response. These hormones trigger the liver to release stored glucose while reducing insulin sensitivity, causing blood sugar to rise sharply even if you're eating less than usual.

What medications should be stopped during diabetes sick days?

Metformin should be temporarily paused during vomiting, diarrhoea, or dehydration due to lactic acidosis risk. SGLT2 inhibitors (like dapagliflozin and empagliflozin) should also be stopped during acute illness as they increase euglycaemic DKA risk. Never stop insulin without medical advice.

What is the difference between DKA and HHS?

DKA (Diabetic Ketoacidosis) is more common in Type 1 diabetes and involves ketone buildup due to insulin shortage. HHS (Hyperosmolar Hyperglycaemic State) is more common in Type 2 diabetes and involves extreme dehydration and very high blood sugar without ketones. Both are medical emergencies requiring urgent care.

What should be in a diabetes sick day kit?

A diabetes sick day kit should include: blood glucose meter with spare strips and batteries, blood ketone meter with strips, thermometer, sugar-free and sugary drinks, easily digestible snack foods (toast, crackers, yoghurt), a written sick day action plan from your diabetes team, and emergency contact numbers (GP, diabetes nurse, NHS 111).

How often should you check blood glucose when ill with diabetes?

When unwell with diabetes, check blood glucose at least every 2-4 hours. If using a continuous glucose monitor (CGM), keep close watch on trends and alerts. If blood glucose exceeds 13 mmol/L, check every 1-2 hours and test for ketones.

What foods should you eat during a diabetes sick day?

During illness, eat small regular portions of easily digestible carbohydrates such as toast, plain crackers, rice, soup, yoghurt, or porridge. The goal is to provide enough carbohydrate to prevent hypoglycaemia while your medication works. Eat small amounts regularly rather than attempting large meals.

Essential Diabetes Care Guide

Sick Day Rules for Diabetes

A Complete Guide to Staying Safe When Illness Strikes

Living with diabetes means every aspect of health requires careful management, and that becomes especially critical when you fall ill. Whether you are dealing with a cold, flu, stomach bug, or infection, sickness can dramatically affect blood glucose levels and increase the risk of serious complications.

View Core Rules Emergency Signs

Understanding the Risk

Why Illness Affects Blood Sugar

When you are unwell, your body releases stress hormones such as cortisol, adrenaline, and glucagon. These hormones are part of the natural immune response, but they also trigger the liver to release stored glucose into the bloodstream while simultaneously reducing insulin sensitivity.

The result is often a sharp and sustained rise in blood glucose levels, even if you are eating less than usual.

Dual Risk for People with Diabetes

Type 1 Diabetes: Increased risk of Diabetic Ketoacidosis (DKA)
Type 2 Diabetes: Risk of Hyperosmolar Hyperglycaemic State (HHS)

Effect of blood sugar levels on body condition showing sugar affecting internal organs liver kidneys heart and stomach

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Stress Hormones

Vomiting and Diarrhoea: A Complicating Factor

These symptoms can complicate matters further by causing dehydration and, in some cases, hypoglycaemia—particularly if you are on insulin or sulphonylureas and cannot keep food down.

Dehydration Risk Low Blood Sugar Dual Risk

The Essential Guidelines

The Core Sick Day Rules

Follow these critical guidelines to stay safe when illness strikes

Never Stop Medication

This is the single most important rule. Even if you are not eating, your body still needs insulin or oral diabetes medications. Stopping medication is one of the most common causes of DKA.

Monitor Blood Glucose

Check your blood sugar at least every 2-4 hours when unwell. If you use a CGM, keep a close eye on trends and alerts. Illness causes rapid and unpredictable swings.

Test for Ketones

If blood glucose rises above 13 mmol/L (~240 mg/dL), test for ketones. Blood ketone levels above 1.5 mmol/L require immediate action.

Stay Hydrated

Aim to drink at least 200ml of fluid per hour. Choose sugar-free fluids when blood sugar is high, and sugary drinks when low or unable to eat.

Eat Little and Often

Replace meals with easily digestible carbohydrates like toast, crackers, rice, soup, yoghurt, or porridge. Small regular portions prevent hypoglycaemia.

Contact Your Team

If unsure about dose adjustments, contact your diabetes team rather than guessing. They can provide personalised guidance for your situation.

Asian woman checking blood sugar level by digital glucose meter healthcare and medical diabetes glycemia concept

2-4h

Check Interval

Blood Sugar Monitoring

Frequent Blood Glucose Checks

Illness can cause rapid and unpredictable swings in blood glucose levels, so more frequent monitoring helps you catch dangerous changes early and respond appropriately.

Recommended Monitoring Frequency

Situation	Frequency
During illness	Every 2-4 hours
Using CGM	Continuous monitoring
When BG > 13 mmol/L	Every 1-2 hours + ketones

Ketone Testing

When and How to Test for Ketones

Ketone testing is particularly important for people with Type 1 diabetes, but anyone on insulin should be prepared to test during illness.

When to Test for Ketones

Blood glucose rises above 13 mmol/L (~240 mg/dL)
Feeling persistently unwell despite normal glucose readings
During any illness with fever or vomiting

Glucometer ketometer lancet and strips for self-monitoring of blood glucose or ketones level diabetes or keto diet

Blood Ketone Levels Guide

Below 0.6 mmol/L Normal

0.6 - 1.5 mmol/L Elevated

1.5 - 3.0 mmol/L High - Call Doctor

Above 3.0 mmol/L Emergency!

Staying Safe

Hydration & Nutrition Guidelines

Older adult holding pill and water taking medication near glucose meter on couch with focused motion diabetes selfcare

Staying Hydrated

Dehydration worsens hyperglycaemia and accelerates the progression towards DKA or HHS. Aim to drink at least 200ml per hour.

Choose Fluids Based on Blood Sugar:

When BG is HIGH

Water, sugar-free squash, clear broth

When BG is LOW or can't eat

Flat lemonade, fruit juice, full-sugar squash

Rustic homemade bread loaf cut in half showing soft crumb texture and crispy crust warm tones

Eating During Illness

If you cannot manage your usual meals, replace them with easily digestible carbohydrate-containing foods. Small amounts regularly are better than large meals.

Suitable Sick Day Foods:

Toast

Crackers

Rice

Soup

Yoghurt

Porridge

Medication Safety

Medication-Specific Considerations

Certain diabetes medications carry additional risks during illness. Understanding these risks helps you take appropriate precautions.

Metformin

Should be temporarily paused during vomiting, diarrhoea, or dehydration because of the risk of lactic acidosis.

SGLT2 Inhibitors

(e.g., dapagliflozin, empagliflozin) Should be stopped during acute illness as they increase risk of euglycaemic DKA.

Insulin

You may need to increase doses during illness. Contact your diabetes team for personalised sick day action plans.

Sulphonylureas / Meglitinides

Risk of hypoglycaemia may increase if food intake is reduced. Monitor closely and have fast-acting glucose available.

Middle aged man sitting at desk consulting with doctor doctor demonstrating insulin pen device during diabetes management appointment

Tip: Ask your diabetes team for a personalised sick day action plan before you need it.

Critical Information

When to Seek Emergency Help

Do not wait to see if things improve on their own. DKA and HHS can progress rapidly, and early intervention dramatically improves outcomes.

Seek Urgent Medical Attention If:

Blood ketone levels above 3.0 mmol/L

This constitutes a medical emergency
Persistent vomiting

Unable to keep fluids or medication down for more than 2 hours
Blood glucose remains above 20 mmol/L (360 mg/dL)

Despite taking correction doses
Signs of DKA

Deep rapid breathing, fruity-smelling breath, or abdominal pain
Confusion, drowsiness, or loss of consciousness

Any altered mental state requires immediate action

Symptoms and complications of Diabetes showing various health indicators

Understanding DKA & HHS

DKA

Diabetic Ketoacidosis

More common in Type 1

HHS

Hyperosmolar State

More common in Type 2

NHS 111 is available 24/7 for urgent medical help when you're not sure what to do.

Be Prepared

Preparing Your Sick Day Kit

Preparation is key. Every person with diabetes should have a sick day kit ready before illness strikes.

Essential Kit Items

Blood Glucose Meter

With spare strips and batteries

Blood Ketone Meter

With spare ketone strips

Thermometer

To monitor fever

Fluids

Sugar-free and sugary drinks

Easy-to-Eat Snacks

Toast, crackers, yoghurt

Sick Day Action Plan

Written guidance from your diabetes team

Emergency Contacts

GP, diabetes nurse, NHS 111

Home first aid kit on blue background elements of the first aid kit

7

Essential Items

Long-Term Health

The Role of General Wellness in Diabetes Management

Effective diabetes management extends well beyond sick day protocols. Long-term resilience depends on consistent self-care.

Quality Sleep

Stress Management

Regular Activity

Proper Nutrition

When the body is well supported on an everyday basis, it is better equipped to handle the additional metabolic stress that illness brings.

Supporting Cognitive Function

Maintaining overall cognitive function and physical resilience is important for anyone managing a chronic condition like diabetes. Many people find that supporting brain health helps them stay alert and make better self-management decisions.

If you are curious about evidence-based approaches to cognitive support, our introduction to nootropics provides a comprehensive starting point.

Learn About Nootropics

Quick Reference

Your Sick Day Action Checklist

Print this checklist and keep it with your sick day kit for quick reference

Essential Sick Day Rules

Never stop your diabetes medication

Unless specifically advised by your healthcare team

Check blood glucose every 2-4 hours

More often if levels are unstable

Test for ketones if BG exceeds 13 mmol/L

Use urine strips or blood ketone meter

Drink at least 200ml fluid per hour

Sugar-free when high, sugary when low

Eat small, regular portions

Easily digestible carbohydrates

Pause metformin and SGLT2 inhibitors

During vomiting, diarrhoea, or dehydration

Seek Emergency Help If:

Ketones above 3.0 mmol/L

Medical emergency - call 999

Vomiting persists

Can't keep fluids/medication down for 2+ hours

BG remains above 20 mmol/L

Despite correction doses

Signs of DKA

Deep breathing, fruity breath, abdominal pain

Confusion or unconsciousness

Any altered mental state

NHS 111 (24/7)

For urgent medical help when you're not sure what to do

Visual Guide

Sick Day Rules Infographic

A visual summary of the key actions to take when you're unwell with diabetes

Sick Day Rules for Diabetes

What to do when illness strikes

Never Stop Medication

Your body still needs insulin or oral meds even if you're not eating

#1 Rule

Check BG Every 2-4h

More often if levels are fluctuating rapidly

2-4 Hours

Test Ketones

If BG rises above 13 mmol/L (240 mg/dL)

>13 mmol/L = Test

Stay Hydrated

At least 200ml per hour

200ml/hr

Eat Little & Often

Toast, crackers, rice, soup, yoghurt

Small Portions

Call Your Team

If unsure about medications or doses

Ask First

Emergency Warning Signs

Ketones >3.0

Persistent Vomit

BG >20 mmol/L

DKA Signs

Confusion

Call NHS 111 or 999 Immediately

Always consult your healthcare team for personalised diabetes management advice

Disclaimer

This article is for informational purposes only and does not constitute medical advice. Always consult your GP, diabetes specialist nurse, or endocrinologist for personalised guidance on managing diabetes during illness. The information provided is based on general guidelines and may not apply to your specific situation.

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